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Mendel University in Brno
Faculty of Forestry and Wood Technology
InWood2015: Innovations in Wood Materials and Processes
International Conference
May 19 – 22, 2015
Conference organisers:
Mendel University in Brno
Zemědělská 1, 613 00 Brno
First Edition 2015
© prof. Dr. Ing. Petr Horáček
ISBN 978-80-7509-255-7
InWood2015: Innovations in Wood Materials and
Processes
Brno, Czech Republic: May 19 – 22, 2015
Edited by P. Horáček, R. Wimmer, P. Rademacher, J. Kúdela, V. Kolářová, and
D. Děcký
Published by:
MENDELU – Mendel University in Brno
Title:
Subtitle:
Editors:
Printing:
Number of pages:
Technical editor:
Petr Horáček, Peter Rademacher, Rupert Wimmer, Jozef Kúdela, Věra
Kolářová, David Děcký
ASTRON Studio CZ a.s.
Green Park, Veselská 699, 199 00 Praha 9
174
David Děcký
Organising Committee
Petr Horáček, Peter Rademacher, Rupert Wimmer, Jozef Kúdela, Vladimír Gryc, Věra
Kolářová, David Děcký
Each paper published in this proceeding was reviewed at least by one member of the
Scientific Committee
Lidia Gurau, František Hapla, Andreja Kutnar, Rastislav Lagaňa, Róbert Németh,
Joris Van Acker, Rupert Wimmer
Acknwoledgement
Supported by the European Social Fund and the state budget of the Czech Republic, project
"The Establishment of an International Research Team for the Development of New Woodbased Materials" reg. no. CZ.1.07/2.3.00/20.0269.
Introduction
Dear participants of the conference InWood2015: Innovations in Wood Materials and
Processes. I would like to welcome you in Brno, Czech Republic, on behalf of the hosting
institution, the Faculty of Forestry and Wood Technology at Mendel University in Brno. We
concentrate on research and academic activities in the areas of forestry, landscaping,
arboriculture, wood processing and furniture design. Our mission is to support sustainable
wood utilization from the perspective of both material and processes. Therefore, we are proud
to organize this conference.
The conference is held within the framework of the project OP VK 2.3 The Establishment
of an International Research Team for the Development of New Wood-based Materials (2013–
2015). During the project we have established cooperation with a number of international
academic and research organisations. I am really glad that we are meeting in Brno and that I
can briefly introduce the visions and strategies we are trying to fulfil.
The forestry and wood processing industry is currently facing many problems and
challenges. It is directly affected by the climate change, the competition within acquiring
timber sources, the changing consumer demand, the increasing competition and complexity of
production processes.
The EU Member States in their National Forest Programmes emphasize the need to improve
the cooperation across industries of the entire forest and wood related sector. One of the
objectives is to create a favourable environment within which the forestry and wood processing
industry can enhance its competitiveness and promote the use and consumption of wood. The
current trend of the global economy development raises the increasingly urgent need to tackle
the problem of limited amounts of exhaustible natural resources. In the context of this global
problem, the EU presented a new challenge in favour of sustainable economic growth, aiming
at the support for economy based on renewable natural resources. It is therefore necessary that
this issue is devoted an increased attention at the level of national economies.
The Czech Republic has sufficient and high-quality supplies of the renewable resource,
which is timber. However, the efficiency of timber utilization is still at a low level, which is
reflected in the lower level of timber appreciation in comparison with the developed EU
countries and the low performance of the forest and wood related sector. The difference is
obvious; while in the Czech Republic primarily wood processing is implemented, in Austria
and Italy there is the production of materials with a higher added value linked to the industry of
finished products, such as furniture and paper, which is a result of the long-term continual
ownership of forest lands and stands with an emphasis on rural areas and with a permanent
innovation process support from the state. The result of the economic policy in the forestry and
wood processing is an economy focused on the export of raw materials and the sale of the
workforce. The specific challenges the forest and wood related sector in the Czech Republic is
currently facing are in particular:
 globalization and supranational management, supranational usage of resources;
 insufficient material, energy and industrial policies;
 the ongoing global climate change – a change in volume, species composition and quality
of timber, including the increasing proportion of hardwood (oak and beech);
 the ongoing socio-economic changes in the society with the importance shifting from the
production to services, and from the primary to the secondary and tertiary processing;
 the differing interests of the stakeholders in the Czech Republic, their large number, the
conflict between global and local processors;
 the dominant position of the state in the timber production;
 financially unexpressed value chain;
 uneven development and usage of yields in the entire chain, including the missing longterm supplier-customer relations, etc.
The problems that remain in the Czech wood processing industry are the low finalisation of
production, a high proportion of exported products with a low level of added value and thus a
low level of added value creation in the sector as well as the unfavourable financial situation of
companies, which are all caused by the absence of an effective cooperation with timber
producers, the disintegration of Eastern markets and a non-standard structure of the timber
trade. In order to find an appropriate solution and increase the efficiency of wood utilization as
well as the competitiveness of wood processors, it is necessary to obtain relevant information,
analyze it and, using the latest scientific knowledge, uncover the causes of the present state and
propose the most appropriate methods, procedures and measures.
These were the bases on which we have built our project. Its aim is to improve the quality
and productivity of science and research at the Faculty of Forestry and Wood Technology,
Mendel University in Brno, by means of a newly established international R&D team. The
outcome of the project is improved current methods and provided new methods of scientific
work, established relationships, and improved quality of the workplace as regards the research
into utilization of wood and wood-based materials with emphasis on applied and industrial
research. The outputs of the involvement of employees in the team is e.g. involvement in
international projects, improvement of competences in science and methodology (research
design, team establishment, communication with research workplaces, intellectual property
protection, presentation and publishing results, etc.), and application of new technologies to
make basic, applied and industrial research at the faculty more efficient. The project focuses on
the research into properties of wood and wood-based materials, modification of the properties,
and development of new materials tailored for their planned utilization. Members of the team
are both junior and senior researchers including foreign experts, whose fields encompass better
utilization of (mainly) beech wood.
There are two key activities in the project – (1) establishment of an international team with
foreign expert leadership and (2) team internationalization – involvement of team members in
international network. These activities are not focused on the research itself, but also the
distribution and sharing of the results. Therefore, at the conference, we would like to present
our own outputs from the project we achieved in cooperation with colleagues from Germany,
Austria, Poland, Slovakia, Slovenia, ... ... ... .... What we appreciate most is the results of the
thermal and chemical modification beech wood properties and the numerical simulations of
these processes.
The final and general result of the project is the establishment of a team with strong
European links, able to present and apply the gained knowledge in the lectures, as well as for
an international scientific forum and the industrial practice.I strongly believe we have been
successful. I am convinced that the prestige of any field is closely related to the effort and will
to achieve excellent results in developing the knowledge and skills. These criteria can be used
to evaluate the lecturing and research performance of our academic staff. Their motivation is
directly linked to the fact that at their lectures and seminars they meet curious and critically
thinking students. Without this inspirational relationship it would not be possible to build a
respected and widely recognized faculty, which in many respects has become a quality
benchmark for others.
I personally believe that the results obtained by all of us will set a very high standard for the
next collaboration and research.
Petr Horáček
Contents
FIRST DAY
Session I: Solid Wood Manufacturing
SHARAPOV, E., KOROLEV, A., KUTNAR, A. & KAMKE, F.A.:
Investigation of the cutting process of thermo-hydro-mechanically treated beech with a simple cutter .................. 13
LAGAŇA, R. & KÚDELA, J.:
Strain development in a wood-solid coating system subjected to asymetric moisture distribution ......................... 15
VAHTIKARI, K., NOPONEN, T. & HUGHES, M.:
Moisture buffering properties of various hardwood species .................................................................................... 17
KOTRADYOVÁ, V., TIŇO, R., ŠPRDLÍK, V. & KALIŇÁKOVÁ, B.:
Potential of natural solid wood surfaces in the built-environment of health care and therapeutic facilities ........... 19
DĚCKÝ, D. & KÚDELA, J.:
Heat load effect on glued joint strength ................................................................................................................... 21
Poster Session
GURAU, L.:
Measuring the roughness of sanded wood surfaces ................................................................................................. 24
ROUSEK, R. & DEJMAL, A.:
Comparison of Hydrothermal and Chemical MethodS of Wood Plasticization ....................................................... 26
HORNÍČEK, S., RADEMACHER, P., KUTNAR, A., KAMKE, F.A. & ROUSEK, R.:
Selected physical properties of viscoelastic thermal compressed wood From fast growing poplar ......................... 28
MILCH, J.,TIPPNER, J., SEBERA, S., KUNECKÝ, J., KLOIBER, M. & NAVRÁTIL, M.:
The numerical assessment of a full-scale truss Reconstructed employing a traditional all-wooden joints .............. 30
Session II: Lignocellulosic Material Science
KOCH, G. & SCHMITT, U.:
Localization of lignin and phenolic compounds in woody tissue by means of scanning UVmicrospectrophotometry .......................................................................................................................................... 33
SERNEK, M., KARIŽ, M., KUTEK KUZMAN, M. & ČOP, M.:
Environmentally friendly materials for wood-basedcomposites: Heat-treated wood, liquefied wood and tannin
foams ........................................................................................................................................................................ 35
FENG, Y. & MEIER, D.:
Supercritical carbon dioxide extraction of value-added chemicals from slow pyrolysis liquids ............................. 37
TRCALA, M.:
Numerical analysis of temperature field in wood during thermal treatment ............................................................ 39
SÁBLÍK, P., NEBEHAJ, E., RADEMACHER, P. & HOFMANN, T.:
Antioxidant assay as a potential assessment of wood extractives antifungal activity .............................................. 41
MISHRA, P.K., CABANE, E., WIMMER, R. & BURGERT, I.:
Using supercritical carbon dioxide as antisolvent for wood modification: preliminary studies ............................... 43
TROPPOVÁ, E. & TIPPNER, J.:
Thermophysical properties of medium density fiberboards measured by pulse transient method ........................... 46
Poster Session
PASCHOVÁ, Z. & RADEMACHER, P.:
Analytical equipment at Mendel University in Brno ............................................................................................... 49
TAUBER, J. & SVOBODA, J.:
Adjustment of air pollution indoors contaminated with cigarette smoke through controlled ionization ................. 51
ŠVEHLÍK, M., TROPPOVÁ, E., TIPPNER, J. & WIMMER, R.:
Heat transfer through a wood-based wall with an air layer ..................................................................................... 53
Session III: Wood and Fiber Property
RADEMACHER, P., WIMMER, R., HORÁČEK, P., GRYC, V. & KÚDELA, J.:
InWood Project: Education and group building for innovations in wood materials and processes ......................... 56
STRAŽE, A., TIPPNER, J. & GORIŠEK, Ž.:
Vibration response of Norway spruce during sorption ............................................................................................ 58
OHLMEYER, M., HELDER, S., BENTHIEN, J.T. & SEPPKE, B.:
Fibre Cube - How to measure fibre size distribution ............................................................................................... 60
ZABIELSKA-MATEJUK, J., FRĄCKOWIAK, I. & STANGIERSKA, A.:
The resistance of composite boards to decaying fungi and mould .......................................................................... 62
BAAR, J:
Evaluation of decay resistance of lignamon ............................................................................................................ 64
ŠTRBOVÁ, M., TESAŘOVÁ, D.& KÚDELA, J.:
Interactions between UV lacquers and wood .......................................................................................................... 66
BRABEC, M., ČERMÁK, P., MILCH, J., SEBERA, V. & TIPPNER, J.:
Analysis of deformation distribution and neutral axis location in thermally modified wood by means of digital
image correlation ..................................................................................................................................................... 68
Poster Session
HLÁSKOVÁ, L. & KOPECKÝ, Z.:
Energy parameters during machining of chemically modified beech ..................................................................... 71
NEVRLÝ, O. & BAAR, J.:
Natural durability of subfossil oak .......................................................................................................................... 73
TABARSA, T.:
Technical report of Paulownia Fortunei planted In Iran .......................................................................................... 75
KLÍMOVÁ, H., TIPPNER, J. & SEBERA, V.:
Elasto-plastic material constants of MDF ............................................................................................................... 77
Session IV: Wood Panels Composites and Processing
NÉMETH, R. & BAK, M.:
Long term, in-service evaluation of strip parquet flooring panels ........................................................................... 80
RUPONEN, J., RAUTKARI, L., OHLMEYER, M. &HUGHES, M.:
Self-bonded birch plywood (Betula pendula, L.): Studies on internal gas pressure during hot pressing and on postmanufacture thermal modification .......................................................................................................................... 82
BUDDENBERG, H., KAMMERLOHER, C. & RICHTER, K.:
Improving quality and yield of rotary peeled beech veneers for plywood production ............................................ 84
ŠIMEK, M. & SEBERA, V.:
Digital image correlation in Furniture testing .......................................................................................................... 86
KWON, J.H. & AYRILMIS, N.:
Effect of heat-treatment of flakes on physıcal and mechanıcal propertıes of flakeboard ......................................... 88
PAAJANEN, O.:
Recent development in the contact drying of veneer ............................................................................................... 90
Poster Session
SELINGER, J. & WIMMER, R.:
A novel low-density sandwich panel made from hemp ........................................................................................... 93
KUMAR, A., RYPAROVA, P., TYWONIAK, J. & HAJEK, P.:
New Innovative process for nanoscale coatings on wood surface using electrospinning technique ........................ 95
SECOND DAY
Session I: Modification of Lignocellulosics
ROWELL, R.M.:
Understanding decay resistance, dimensional stability and strength changes in acetylated wood ........................... 98
FOJUTOWSKI, A., NOSKOWIAK, A. & KROPACZ, A.:
Increase in the resistance to biodegradation of black poplar wood by thermomodification .................................. 100
BICKE, S. & MILITZ, H.:
Weathering stability of PF-treated veneer products from beech wood .................................................................. 103
PORI, P., OREL, B., VILČNIK, A., ŠKAPIN, A.S. & PETRIČ, M.:
Influence of reaction conditions on the crystalline form of hydrothermally deposited TiO 2 on surfaces of spruce
wood....................................................................................................................................................................... 105
ČERMÁK, P.:
Unevenly distributed thermal modification of wood: preliminary study – density profiles ................................... 107
PAŘIL, P., BAAR, J., PRUCEK, R. & KVÍTEK, L.:
Antifungal effect of copper and silver nanoparticles against white-rot and brown-rot fungi ................................. 108
ŠPRDLÍK, V., MIHAILOVIĆ, S., BRABEC, M. & KLÍMOVÁ, H.:
Bonding strength of ammonified beech veneer ...................................................................................................... 110
FODOR, F.P., POZSGAY, B. & NÉMETH, R.:
The effect of the process parameters of thermal modifications on the physical and mechanical properties of wood
............................................................................................................................................................................... 112
Poster Session
ČECH, P. & TESAŘOVÁ, D.:
Comparing the voc emissions of heat treated wood with and without finishing .................................................... 115
KOIŠ, V., DÖMÉNY, J. &TIPPNER, J.:
The effect of microwave plasticization and densification on density and density profile ...................................... 117
BORŮVKA, V., PÁNEK, M., ZEIDLER, A. & DOUBEK, S.:
Improving the dimensional stability of wood modified by silicon-based chemicals ............................................. 119
Session II: Advanced Wood - Polymer Composites
AYRILMIS, N. & KAYMAKCI, A.:
Physical, mechanical, and thermal properties of wood plastic nanocomposites reinforced with multi walled carbon
nanotubes............................................................................................................................................................... 122
RIEGLER, M., SYKACEK, E. & WIMMER, R.:
Processibility of wood-plastic composites on a single-screw extruder ................................................................. 124
FRYBORT, S., KRENKE, T., MÜLLER, U. & MAURITZ, R.:
A novel wood composite material ......................................................................................................................... 126
GHORBANI, M., LIEBNER, F., VAN HERWIJNEN, E., PFUNGEN, L., KRAHOFER, M. & KONNERTH, J.:
Selected characteristics of lignin-phenol-formaldehyde resole adhesives ............................................................. 128
KLÍMEK, P., MEINLSCHMIDT, P. & WIMMER, R.:
Microscopic swelling of components in wood based panels: First trials ............................................................... 130
MAHRDT, E., PINKL, S., SCHMIDBERGER, C., VAN HERWIJNEN, H. W. G & GINDL-ALTMUTTER, W.:
Light-microscopic detection of nanocellulose-reinforced adhesives in particleboards ......................................... 133
Poster Session
KAYMAKCI, A. & AYRILMIS, N.:
Effect of nano-clay on some physical and mechanical properties of wood polymer nanocomposites .................. 136
KWON, J.H., AYRILMIS, N. & HAN, T.H.:
Effect of core layer composıtıon on water resıstance and mechanıcal propertıes of hybrıd partıcleboard ............ 138
AYRILMIS, N., KWON, J.H., LEE, S.H. & HAN, T.H.:
Mechanical performance of laminated veneer lumber bonded with urea-formaldehyde containing mıcrofibrillated
cellulose................................................................................................................................................................. 140
HÝSEK, Š., BÖHM, M. &WIMMER, R.:
Optimization process of natural-fibre nonwovens ................................................................................................. 142
Session III: Innovation Trends, Environment & Markets
TEISCHINGER, A.:
Industry 4.0 – a new approach for wood manufacturing ....................................................................................... 145
RUMINSKI, N. & HAPLA, F.:
Grading of spruce timber using laser induced fluorescence (LIF) ........................................................................ 147
EICHHORN, S., NÉMETH, R. & HAPLA, F.:
Analysis of different wood product lines of sweet chestnut (Castanea sativa Mill.) ............................................ 150
VAN ACKER, J., DEFOIRDT, N., DE BOEVER, L. &VAN DEN BULCKE, J.:
European planted poplar as sustainable resource for multipurpose end uses ........................................................ 153
GURAU, L. & CIONCA, M.:
From secondary wood resource to value added eco-products ............................................................................... 156
JANISZEWSKA, D., FRĄCKOWIAK, I. & ANDRZEJAK, C.:
Some aspects of using post-consumer wood in particleboard production ............................................................. 159
MEINLSCHMIDT, P. &MAURUSCHAT, D.:
Up- and down-cycling of waste wood in Europe .................................................................................................. 161
Poster Session
RANACHER, L. & STERN, T.:
Wood you believe it? Pro-environment is pro-forestry .......................................................................................... 163
SHAKERI, A., TAHMASBI, A. & TABARSA, T.:
Green particleboard using free formaldehyde soya protein binder ........................................................................ 167
KRÁL, P. & KLÍMEK, P.:
Plywood: Novel solutions for sustainable industrial production ............................................................................ 169
Author's Alphabetical Index
First Day
Session I
Solid Wood Manufacturing
InWood2015: Innovations in wood materials and processes
Brno, Czech Republic, 19–22 May 2015
INVESTIGATION OF THE CUTTING PROCESS OF THERMO-HYDROMECHANICALLY TREATED BEECH WITH A SIMPLE CUTTER
E. Sharapov1, A. Korolev1, A. Kutnar2,*, F.A. Kamke3
1
2
Volga State University of Technology, Institute of Forest and Natural Resources Management
3 Lenin sq., Yoshkar-Ola, Republic of Mari El, 424000, Russian Federation
e-mail: [email protected]
University of Primorska, Andrej Marušič Institute, Muzejski trg 2, SI-6000 Koper, Slovenia; University of
Primorska, Faculty of Mathematics, Natural Sciences and Information Technology, Glagoljaška 8, 6000Koper, Slovenia.
*
3
Oregon State University, Department of Wood Science and Engineering
119 Richardson Hall, Corvallis, OR, USA
INTRODUCTION
The ability to control the properties of thermo-hydro-mechanically (THM) treated wood
provides a variety of potential innovative uses for THM modified wood. Past studies have
investigated the structural, chemical and mechanical properties as well as bonding
characteristics of THM treated wood. Although many aspects of THM treatments were studied
in the past, the fundamentals of the influence of densification process on wood cutting process
with simple cutter and generated surface quality of densified wood was not studied in the past.
Therefore, the influence of densification process on the cutting process with simple cutter of
untreated and THM treatedwood was the preliminary objective of this paper.
material and methods
Specimens of beech wood (Fagus sylvatica L.) were conditioned in a controlled
environment at a relative humidity (RH) of 65% and temperature of 20 °C until equilibrium
moisture content of approximately 12 % was achieved. The strips were planed to reduce
thickness to 6 mm (radial), and cut to a length of 400 mm (longitudinal) and width of 50 mm
(tangential).
The viscoelastic thermal compression (VTC) process was performed in a pressurized vessel
equipped with a heated hydraulic press at temperature of 170 °C. The specimens were
compressed from initial thickness of 6.08 mm to 2.88 mm resulting in density ratio of 103%.
After the VTC process the specimens were conditioned to equilibrium at 20 °C and 65% RH.
Longitudinal cutting of specimens was studied on Pendular laboratorymachine. The
influence of wedge angle β and nominal chip thickness (h) on mechanical work of cutting
process with simple cutter A (J) were determined.
The cutting was performed in the longitudinal direction on specimens that were supported
with two specimens. The values of wedge angle β examined were 20, 25, 30, 35, and 40
degrees, while the examined nominal thicknesses of chips h were 0.05, 0.1, 0.15, 0.2, 0.25, and
0.3 mm. Every combination of input factors had 10 repetitions. The fixed cutting parameters
were clearance angle α = 12 deg., Υ - rake angle (Υ=90-(α+β) andinitial edge rounding ρ0= 6-7
μm.
13
RESULTS
The cutting process using simple cutter of untreated and THM treated beech specimens
showed that the increased density of THM treated wood influences the actual chip thickness h.
The influence is increasing with increased nominal thickness and increased sharpness angle
(Figure 1).
For untreated wood mean value of work of cutting process A is decreasing with decreasing
edge angle β and increasing with increasing nominal thickness hnom (Figure 2). On the other
hand, work of cutting process A of THM treated wood first decreases with the wedge angle β,
reaches minimum values at wedge angle β near 30° and increases again with increased wedge
angle β (Figure 2).
Actual chip thickness hact, mm
0,5
0,4
0,3
0,2
0,1
0,0
35
Wed 30
ge a
25
ngle
,
0,20
0,15
20
0,25
ess
ickn
ip th
0,05
al ch
in
Nom
0,30
, mm
h nom
0,10
Figure 1: Actual chips thicknesshact, mm of untreated (filled graph) and THM treated (frame graph) beech
specimens in dependence onwedge angle β, deg.
Figure 2: Experimental points (mean values) and estimating surface for work of cutting process A [J] of untreated
specimens (left) and THM treated (right) wood.
CONCLUSION
Thecutting of densified wood is comparable with the cutting of undensified wood, while
with certain initial parameters of wood specimens and cutting operation the work of cutting
process can be lower. Therefore, in the case of densified wood optimal cutting parameters can
be selected when machining it.
14
STRAIN DEVELOPMENT IN A WOOD-SOLID COATING SYSTEM
SUBJECTED TO ASYMETRIC MOISTURE DISTRIBUTION
R. Lagaňa* & J. Kúdela
Technical University in Zvolen, Faculty of Wood Sciences and Technology, Department of Wood Science
T. G. Masaryka 24, 96053 Zvolen, Slovakia
*
e-mail:[email protected]
INTRODUCTION
The main cause of cracks in solid coatings applied on wood is assigned to stresses generated
in the coating already during the curing or drying of the coating material or stresses generated
by moisture, heat and mechanical loading to the system wood – solid coating. Wood is a
hydrophilic material; consequently, the stresses associated with moisture loading are especially
important.
Stresses in solid coatings are determined by various methods. The most frequent method for
stress determination in coating films is the method of beam deflection. The coating material is
applied on a metal strip with clearly defined properties and the strip´s deflection is measured
experimentally. The method is used for determining stresses occurring in solid coatings during
curing or under heat loading. There also exist several methods for calculating these stresses [1−4].
As the coating adhesion to the substrate is affected not only by the properties of the coating
material but also by the properties of the substrate and by the interactions at the phase boundary
substrate – coating material, it is reasonable to suppose that the interactions of this material with
wood will be different from its interactions with a metal. This means that the stress patterns will
be different, too. In addition, the ‘metal strip’ method is not feasible for determining stresses
developed under moisture loading. For these reason, the metal strip has been substituted by a
wooden one. In this case, however, the equations used for stress calculation from the beam
deflection give very changed stress results [4]. So, there is a need to study strain distribution
across the whole system – coating during moisture loading in more details.
The aim of this paper is to describe complex development of strains in wood – coating
system subjected to asymmetric water diffusion. The focus was on study of strain profiles
across the specimen thickness and over their coated and uncoated faces.
MATERIAL AND METHODS
The experimental works were conducted on radial beech specimens (Fig.1). Before the
testing, the specimens were conditioned to a moisture content of about 8 %. The specimens
were treated on the surface with a commercially produced polyurethane lacquer, applied in 4
layers. The lacquer was applied only to one face of each specimen.
Sample sides were coated with a thin silicone film in order to prevent moisture movement in
longitudinal and radial directions. A random pattern required by DIC method was applied to
one cross section of each sample. The samples were placed on two stable rakes inside of a glass
vessel. The distance between samples was 11 mm. Thereafter, the vessel was closed and
supplied with redistilled water. The uniform humidity distribution throughout the vessel (≈100
%) was attained with a fan. Displacement field of RT surface points were mapped with the
system Aramis 3D.
The radial strain was evaluated from points (facets) spaced 4.5 mm in the radial direction.
This distance was small enough to allow us to neglect the sample curvature in strain calculation
15
and long enough to cancel out the local shrinkage of early/late wood. The distance between the
radial strain lines in the tangential direction was 0.26 mm. Simultaneously, the specimen´s
deflection was measured in the specimen´s center as a distance between the 70 mm central line
and the midpoint. The test lasted for 2 weeks and strain measurements were repeated every
30min.
42
42
Figure 1: Test specimen; a) before surface treatment, b) after surface treatment.
RESULTS AND DISCUSION
The results revealed a linear character of the strain profiles across the thickness of the bent
samples (Fig.2). Asymmetric water movement resulted in uneven swelling across the thickness. This
caused bending of the samples and continuous shifting of the neutral axis from the center towards the
coated face (Fig.2). In the initial phases of bending, the nature of strains in the coating film was
compressional, later, with equilibrated moisture distribution in the specimen it was changing to
tensional – as a result of wood swelling across the whole thickness (Fig.3).
Figure 2: Strain distribution across the thickness
of wood-coating sample during the first 3.5 hours
in moist environment
Figure 3: Bending deflection and coating strain
in moist environment
CONCLUSION
A basic principle that “plane sections remain plane” is valid also for bending caused by
asymmetric water distribution.
Strain at the coated surface is initially in compression and later when water progresses in
wood it continuously changes to tensional strain due to the prevailing wood swelling.
REFERENCES
[1] Perera, D. Y. (1998) Measurement of Stress in Multicoat Systems. J Coat Technol 70:69–75
[2] Saderson T. (2008) On the evaluation of residual stresses in bi-layer materials using the bent strip
method. Surf Coat Technol 202(8):1493–1501. doi: 10.1016/j.surfcoat. 2007.07.004
[3] de Meijer, M., Nienhuis, J. (2009) Influence of internal stress and extensibility on the exterior
durability of wood coatings. Prog Org Coat 65:498–503
[4] Kúdela J., Rešetková, M. (2012) Stresses in solid coatings on surface treated beech specimens,
calculated from deflection values during wetting. Acta Facultatis Xylologiae. 54(2):67–78
16
MOISTURE BUFFERING PROPERTIES OF VARIOUS HARDWOOD
SPECIES
K. Vahtikari1, T. Noponen2, M. Hughes3
1
Aalto University, School of Chemical Technology
Vuorimiehentie 1, 02150 Espoo, Finland
2
Aalto University, School of Engineering
Sähkömiehentie 3, 021450 Espoo, Finland
3
Aalto University, School of Chemical Technology
Vuorimiehentie 1, 02150 Espoo, Finland
INTRODUCTION
Moisture buffering has been studied from various perspectives, but research has mainly
focused on softwood species, especially on spruce and pine. Sometimes, especially in the field
of construction, wood has been presented without specifying the species. Nevertheless, there is
a need for information regarding the moisture buffering behavior of wood, since designers and
architects have a growing interest in using wood in interiors. Information about the
performance of wood material in different temperature and humidity conditions should be
easily accessible to support the aim to create functional wooden surfaces. Another significant
perspective is different surface treatments and their effect on the performance of wooden
surfaces, e.g. moisture buffering capacity. This study will present the results from the initial
screening of the performance of six hardwood species in two humidity levels: RH33 and
RH75.
The moisture buffering test followed for the most part the protocol of Nordtest Method [1].
The species in the study were ash, birch, black alder, elm, maple and oak. Dimensions of the
planed test boards were 325mm*80mm*13mm. Only one side of the board (radial or tangential
surface) was exposed to water vapor; the other five sides were sealed with aluminum tape. The
exposed surfaces had the same area in both grain directions. The set value for the high
humidity load was RH75, but according to the monitored values using Scanntronik Hygrofox
Mini data logger, the higher level of relative humidity was 80%. Similar 5% difference was
also found on the lower RH level: instead of 33% the value was 38%. Test boards were preconditioned in RH50, T=23ºC for several weeks before testing.
RESULTS
Figure 1 shows that in most cases the tangential surfaces adsorbed more water than radial
surfaces. Tangential surfaces reveal the cross section of ray cells which increases the porosity
of the surface along with the pores. Elm, ash and oak are all ring-porous hardwoods, but there
are differences in the amount of tyloses: they are abundant in oak, fairly abundant in ash and
usually sparse in elm [2]. Black alder, maple and birch belong to diffuse-porous hardwoods
and the size of the pores is small. The flow of water vapor in birch is inhibited by small pits
17
which may, at least partly, explain the difference to maple [2]. Figure 2 presents the density of
the samples at the end of the test after 16 hours in RH33. All ring-porous species in this study
have similar density whereas the density of diffuse-porous species varied.
Figure 1: The change of the moisture content (%) during adsorption and desorption cycles. Adsorption cycle lasted 8
hours and desorption 16 hours. X-axis does not show the time scale. The small t and r stand for tangential and radial and
capital letters for the species: E=elm, A=ash, B=birch, BA=black alder, M=maple and O=oak.
Figure 2: The density of the samples at the end of the test.
CONCLUSIONS


The size and number of apertures does not solely explain the differences in the
moisture buffering.
The density of the studied species had only a small variation and thus the following
tests will focus on the effect of density.
ACKNOWLEDGEMENTS
Aalto Energy-efficiency research programme AEF (project Wood Life) and Wood Wisdom
Net project Wood2New have funded this work.
REFERENCES
[1] Rode C, Peuhkuri R, Mortensen LH, Hansen KK, Time B, Gustavsen A, Ojanen T, Ahonen J,
Svennberg K, Harderup LE, Arfvidsson J (2005) Moisture Buffering of Building Materials.
Report. Technical University of Denmark.
[2] Hoadley BR, (1990) Identifying wood. The Taunton Press, Newton
18
POTENTIAL OF NATURAL SOLID WOOD SURFACES IN THE BUILTENVIRONMENT OF HEALTH CARE AND THERAPEUTIC
FACILITIES
V. Kotradyová1,*, R. Tiňo2, V. Šprdlík3, B. Kaliňáková2
1
2
Slovak University of Technology in Bratislava, Faculty of Architecture
Námestie Slobody 19, 81245 Bratislava, Slovakia
*
Slovak University of Technology in Bratislava, Faculty of Chemical and Food Technology Radlinského 9,
81237 Bratislava, Slovakia
3
Mendel University in Brno, Faculty of Forestry and Wood Technology,
Zemědělská 3, 61300 Brno, Czech Republic
INTRODUCTION
Natural solid wood as material with a high potential for humanisation of environment and
reaching a state of complex comfort, particularly in health care and wellness facilities, has
disadvantages such as more demanding maintenance to keep the surfaces clean, disinfected and
water resistant/hydrophobic or superhydrophopic. To prevent these issues, high resistant
chemical/synthetic finishes are used in the standard conditions. But with chemical finishing of
its surface many positive effects of the wood on healthy microclimate are lost.Paper presents
the main advantages of wood in its natural form for the microclimate and its anti-stress impact
for users.
There are two hypotheses contributing to the statement that wood is suitable for the spaces
with higher maintenance conditions. First is that wood without additional chemical finishing
has an natural antibacterial (antimicrobial) effect [1], [2]. Second is that it is possible to
provide a surface modification with the aim to reach the state that wood can be hydrophobic, or
even superhydrophobic and thus easy to maintain after modification by plasma or by finishes
based on nanotechnologies and biomimetic. Hydrophobic character of the wood surface
provide environment, which is not suitable for various microorganisms to live as the water is
essential for their life.
Low temperature plasma operating in an oxidizing atmosphere such as air is efficient in
introducing polar functional groups to the wood surface [3]. These are consequently
responsible for improved surface wettability [4]. However, similarly to other polymers, the
effect of plasma assisted enhancement of wood wettability is not stable in time [5]. So called
aging effects manifest itself as a slow (in order of days) gradual recovery from hydrophilic
character to the initial character of wood surface and continues further towards the
hydrophobic state that never completely gets back again to the initial state. Plasma activation
can be also used for the creation of hydrophobic thin coatings on the wood surfaces [6].
Typically a spray-casting technique is employed, in which nanoparticle-polymer suspension is
atomized and dispersed on a wood surface. Plasma provides multifunctional treatment of the
wood. Due to presence of UV light and reactive chemical species in the plasma discharge,
plasma sterilization is welcomed side-benefit. A significant reduction in the number of viable
microorganism colonizing the wood structure before application of the coating system leads to
19
avoidance, or slowdown of the biological degradation by growth of microorganism colonies
(bacteria and fungi) underneath the paint film.
At the end, the combination of the first two hypotheses - wooden surfaces after plasmatic
modification and its natural antimicrobial effect - is explored. The paper presents examples and
authors’ own tests supporting these hypotheses.
Figure 1: Survival of the bacteria on the surface of a pine block at 0.5 and 20 hours, respectively.
CONCLUSIONS
Studies about antibacterial activity of wood together with results of our own microbiological
test show that wood, as a natural material, does not support growth and reproduction of
bacteria; quite the opposite, bacterial survival ability on the wooden surface decreases with
time. It appears that the wooden surface (floor, furniture) may be suitable in an environment
with a higher amount of bacteria such as health care facilities – in ambulances, inpatient wards
and waiting areas.
ACKNOWLEDGEMENT
This work was supported by the Slovak Research and Development Agency under the
contract No. APW-04594-12 – Interaction of Human and Wood – Humanisation Potential of
Wood.
REFERENCES
[1] Stingl R, Domig K (2011) Holz und Hygiene (State of the Art in Kurzform), IHF, BOKU
Vienna
[2] Milling A, Kehr R, Wulf A, Smalla K (2005) The use of wood in practice – a hygienic risk?
Holz als Roh-und Werkstoff 63:463-472. doi:10.1007/s00107-005-0064-x
[3] Ondrášková M, Ráhel' J, Zahoranová A, Tiňo R, Černák M (2008) Plasma Activation of Wood
Surface by Diffuse Coplanar Surface Barrier Discharge. Plasma Chem Plasma Process 28:203211. doi:10.1007/s11090-007-9117-8
[4] Bonn D, Eggers J, Indekeu J, Meunier J (2009) Wetting and Spreading. Rev Mod Phys 81:739805. doi:10.1103/RevModPhys.81.739
20
HEAT LOAD EFFECT ON GLUED JOINT STRENGTH
D. Děcký1,* & J. Kúdela1,2
1
2
Mendel University in Brno, Faculty of Forestry and Wood Technology
Zěmědělská 3, 61300 Brno, Czech Republic
*
T. G. Masaryka 24, 96053 Zvolen, Slovak Republic
INTRODUCTION
Glues used in wood bonding provide high quality joints [1]. However, the quality of
adhesively bonded joints in wood structures is influenced by the environment to which the
construction is exposed. A special risk to glued construction bearing elements is heat loading.
The negative influence of heat is evident on altered properties of wood itself and of glue [2].
This influences directly the service behaviour of constructions elements [1]. From this
viewpoint, proper type of glue is important [3].
The aim of this work was to assess experimentally permanent changes in performance of
joints glued with selected adhesive types exposed to heat load.
MATERIALS AND METHODS
Permanent changes in shear strength of glued joints loaded with heat were studied on wood
panels obtained by gluing 9 spruce prisms. The panels had a surface 478  650 mm2 and a
thickness 33 mm (Fig.1a). Their moisture content was 12%. The glue types used were three –
polyvinyl acetate (PVAc), epoxide and phenolic-resorcinol (PR). One surface of each panel
was exposed to heat emitted from a thermal radiation source with a power of 50 kW·m–2 (over
25 minute period). Thermocouples were mounted on the other surface of the panel to measure
obtain temperature profiles across the panel surface and the panel thickness during heat
loading. Thereafter, the panels were cooled. From the cooled panels and from the control (heat
untreated) panels, there were sawn specimens for shear testing (Fig. 1b) (). Shear strength was
assessed with specimens conditioned at φ = 65 %, t = 20 °C.
Figure 1: The shape and dimensions of a panel (a) and a test specimen (b)
RESULTS
Table 1 shows obtained shear strength results of the tested adhesive bonds both before and
after heat loading. There were not manifested significant differences due to the glue type in the
specimens before heat loading. In all cases, the failure occurred in wood.
21
Table 1: Basic statistical characteristics of shear strength in glued joints
Basic
statistical
characteristic
x [MPa]
s [MPa]
n
FR
glue
5.63
1.28
87
Before heat loading
Epoxide
PVAC
glue
glue
5.03
1.06
77
4.97
1.38
73
FR
glue
4.87
1.23
76
After heat loading
Epoxide
PVAC
glue
glue
1.58
0.88
80
3.03
1.21
87
The heat loading induced qualitative changes in the glued joints in the panels, which was
also reflected on the strength as such. In all cases, the shear strength was significantly lower
than in the corresponding controls. The lowest difference was obtained in case of panels glued
with (PR) glue, the biggest in panels glued with epoxide glue.
The examination with the aid of differential raster calorimetry identified a considerable
degradation of (PR) glue as late as at 530 °C. This was observed only on the panel surface, to a
depth of ca 1–2 mm, where strong wood degradation occurred. With increasing depth, there
were no distinct changes in (PR) glue and impairments occurred in wood.
The response of epoxide glue to heat load was more sensitive. The impaired shear surfaces
manifested three degradation zones differing in quality. On the panel surface, wood
degradation as well as glue decomposition was considerable. In the second zone, the glue melt
due to heat and could not re-join the wood after cooling. In the third zone, the heat caused such
glue degradation that the joint was destroyed. Moreover, the wood in this zone was impaired
by shear. The proportions of these three zones correlated with temperatures measured on the
cross section. In the cases when the glued points were loaded with heat, this third zone did not
occur.
In case of joints glued with (PVAc) glue, there were observed similar changes as in the case
of epoxide glue. The (PVAc) decomposition started at lower temperatures than in epoxide, but
the shear strength values were higher. This was because the (PVAc) softened under heat, but
after cooling this glue could restore its bonds with wood. The quality of these secondary bonds
was lower compared to the original.
CONCLUSIONS
In all three cases, heat loading caused permanent changes in the glued joints. The extent of
these changes depended on the glue type, with the highest resistance observed in the phenolicresorcinol glue. The biggest permanent changes were observed in panels glued with the
epoxide glue.
REFERENCES
[1] Custódio J, Broughton J, Cruz H (2009) A review of factors influencing the durability of
structural
bonded
timber
joints.
Int
J
Adhes
Adhes
29:173-185.
doi
10.1016/j.ijadhadh.2008.03.002
[2] Clauß S, Joscak M, Niemz P (2011) Thermal stability of glued wood joints measured by shear
tests. Eur J Wood Prod 69:101-111. doi 10.1007/s00107-010-0411-4
[3] Frangi A, Fontana M, Mischler A (2004) Shear behaviour of bond lines in glued laminated timber
beams at high temperatures. Wood Sci Technol 38:119-126. doi 10.1007/s00226-004-0223-y
22
Session I
Solid Wood Manufacturing
Poster Session
MEASURING THE ROUGHNESS OF SANDED WOOD SURFACES
L. Gurau
Transilvania University of Brasov, Faculty of Wood Engineering
B-dul Eroilor 29, 500036 Brasov, Romania
INTRODUCTION
No agreed guidelines exist in wood surface metrology for measuring the roughness of wood
surfaces. The existing general standard methods are not usually applicable to wood. Measuring
and filtering wood surface data is complex because wood contains a specific anatomical
structure that creates a surface texture independent of any processing. When this anatomical
roughness is greater than the roughness due to processing, it creates distortions when
processing the data and the surface appears rougher than it really is [8].Therefore, the effect of
wood anatomy on the measuring results is important and a reliable metrology method capable
of overcoming the biasing anatomical effect must be developed [1].
Roughness parameters can be calculated from measured surfaces that allow comparisons to
be made between different processing variables. If these parameters are to be useful, they must
be repeatable, which implies some standardisation of factors affecting their measurement and
calculation. Such factors include the measuring instruments, measuring and filtering methods
and the choice of standard or non-standard parameters applicable to wood.
MATERIAL, METHODS AND RESULTS
The choice of instrument type. A Taylor Hobson instrument, TALYSCAN 150, was used
that could apply two of the most common measuring techniques, laser triangulation and stylus
scanning, with a single handling of the specimen. Since only the scanning head was changed,
this instrument offered the advantage of inspecting exactly the same area with both methods.
Their suitability for wood surfaces was evaluated in terms of their repeatability and their ability
to detect peaks and valleys.The stylus was better able to detect surface irregularities than the
laser triangulation device, and was more accurate and repeatable.
The choice of measuring resolution.The best resolution is the lowest resolution that still
allows an accurate evaluation of roughness parameters.The effect of varying the resolution was
investigated on beech and spruce specimens sanded with P1000 grit size and oak specimens
sanded with P1000 and P120 grit size, scanned at 1 m resolution. Lower resolutions of 2, 5,
10, 20, 50 and 100 m were obtained as sub-sets of the original data. Since the datasets were
from the same surfaces and differed only in their resolution, the effect of choosing different
resolutions on the roughness parameters could be clearly observed. It was found that although
the resolution was sensitive to the grit size, a value of 5 m was reliable enough to be
recommended for measuring wood surfaces sanded with commercial grit sizes.
The choice of evaluation length. The reliability of the evaluation of any roughness
parameters depends on the length of the profile that is evaluated. A long evaluation length
increases the reliability of the roughness parameters since it increases the probability of
recording a profile that contains the variation of the surface. The sensitivity of the roughness
parameters Raand RSm from [3] and Rk from [5] to the evaluation length was investigated on
profiles from tangential surfaces of oak and spruce sanded with P120 grit. The roughness
parameters were initially calculated over a 5 mm length, taken as the first 5 mm of the profile.
The evaluation length was gradually increased to 50 mm. It was found that wood does not
24
comply with the evaluation length requirements of the general standard [2]because of its
variable anatomy. An evaluation length of 50 mm was the most suitable for wood, because the
amount of variation of the roughness parameters stabilised.
Filtering the primary profile. The presence of wood anatomy causes distortion when
filtering with common filters as [4] and [6]. A number of profile filters were examined and the
one that introduced the least distortion was the Robust Gaussian Regression Filter (RGRF),
described in [7]. It is a modification of the Gaussian filter from [6] and is applied iteratively to
a data set until a convergence condition is met.
Separating the processing roughness from the wood anatomy. A straightforward tool for
separating the wood anatomy from processing data is by thresholding the profile by means of
second derivatives in the material ratio curve of the roughness profile. Processing roughness
was defined as the core roughness of a profile where the outlying peaks and valleys have been
replaced with zeros. The anatomical roughness was taken as the valleys below the lower
threshold, while the peaks above the upper threshold represent the fuzziness.
Calculation of processing roughness parameters. The general standards give a variety of
quantitative measures of surface roughness. A single value of these parameters is defined on a
nominal interval called the sampling length. The length used for assessing the profile is called
the evaluation length, which in generalshould contain five sampling lengths. However, given
the variability in wood anatomy, roughness parameters calculated over the evaluation length
were more reliable than those defined on sampling lengths, and therefore are recommended for
a wood surface.
CONCLUSIONS
A comprehensive set of recommendations to evaluate sanded wood surfaces was developed
by the author and presented in this paper. The recommendations cover the choice of instrument
type, the measuring resolution, the minimum evaluation length, aspects of filtering and
separation of processing roughness and anatomical irregularities and calculation of roughness
parameters. This paper presented a review of this method and its potential in assessing the
quality of sanded wood surfaces eliminating the biasing effect of wood anatomy.
REFERNECES
[1] Gurau L, Mansfield-Williams H, Irle M (2011) Evaluating the roughness of sanded wood
surfaces. In: J. Paulo Davim (ed) Wood Machining. ISTE-Wiley, London, pp 217-267
[2] ISO 4288 (+ Cor 1: 1998), Geometrical product specifications (GPS) – Surface texture. Profile
method. Rules and procedures for the assessment of surface texture.
[3] ISO 4287 (1997) + Amd1 (2009) Geometrical product specifications (GPS). Surface texture.
Profile method. Terms. Definitions and surface texture parameters
[4] ISO 13565-1 (1996)+ Cor 1 (1998) Geometrical product specifications (GPS) – Surface texture.
Profile method. Surfaces having stratified functional properties. Part 1: Filtering and general
measurement conditions
[5] ISO 13565-2 (1996) + Cor 1 (1998) Geometrical product specifications (GPS) – Surface texture:
Profile method. Surfaces having stratified functional properties. Part 2: Height characterisation
using the linear material ratio curve
[6] ISO 16610-21 (2011) Geometrical product specifications (GPS) -- Filtration -- Part 21: Linear
profile filters: Gaussian filters
[7] ISO/TS 16610-31 (2010) Geometrical product specification (GPS) – Filtration. Part 31: Robust
profile filters. Gaussian regression filters
[8] Tan PL, Sharif S, Sudin I (2012) Roughness models for sanded wood surfaces, Wood Sci
Technol 46(1-3): 129-142
25
COMPARISON OF HYDROTHERMAL AND CHEMICAL METHODS
OF WOOD PLASTICIZATION
R. Rousek*& A. Dejmal
Mendel University in Brno,Faculty of Forestry and Wood Technology, Department of Wood Science
*
INTRODUCTION
The process of wood plasticization and densification has been known for decades. It is used
for improvement of mechanical properties of low density wood. Many scientists also focus on
modification of medium density beech wood (Fagus sylvatica) [3,4], which is widely used in
industry.
Prior to densification wood can be plasticized by hot saturated steam at temperatures close
to 100°C [3,5,6]. Then it is compressed and stabilized by drying [5,6]. To prevent compression
set recovery in wet condition, compressed wood is post-treated in saturated steam at
temperatures from 140°C to 200°C [1]. It can be one stage of complex thermo-hydromechanical wood processing [2,3].
The most promising chemical method is plasticization with anhydrous ammonia, which is
very rapid and effective [3,4]. Shaping with this method results in permanent shape to which
the wood will return even after soaking with water [3]. Ammonified and densified material
called lignamon, which was produced in industrial scale, was developed by Stojčev [4].
In this study the influence of growth ring angle on densification process of European beech
wood (Fagus sylvatica) was evaluated. Two different methods of wood plasticization were
compared. Specimens were plasticized by hot steam or gaseous ammonia and then compressed
in the transverse direction with a speed of 8 mm.min-1.
RESULTS
Results obtained by digital image correlation method (DIC) show a significant influence of
the growth ring angle on strain distribution (Figure 1). Variability of vertical strain εyy was the
highest for growth ring angle of 15° (almost radial compression). The lowest variability of
vertical strain εyy was observed in a specimen with growth ring angle of 75° (almost tangential
compression). A strong linear correlation between the growth ring angle and the mean value of
Poisson ratio was found. Specimen compressed in the radial direction showed the highest
value.
0°
15°
30°
45°
60°
75°
90°
Figure 1: Set of European beech specimens and DIC (Digital Image Correlation) results of transversal compression test
(26% compression) after hot steam plasticization. Color shows vertical strain εyy (Lagrange) where blue and violet
represent maximum strain and red indicates minimum.
26
Both plasticization methods show a significant decrease in the pressure necessary for the
densification but hot steam showed slightly better results (Figure 2). Conditions were:
temperature of specimens after hot steam plasticization was 100°C and moisture content was
33.5%.
Specimens exposed to ammonia gas increased weight (WPG) by 12% and were tested at a
normal temperature (24°C). Maximal saturation of standard specimens (20x20x30mm) can be
reached after 3 hours.
Stress σ [MPa]
Tangential compression
Reference
Ammonia
gas
Hot steam
Strain ε
Figure 2: Compression strength test of European beech wood (Fagus sylvatica) in tangential direction - detail.
Specimens were plasticized with ammonia gas or hot steam or remained untreated as reference specimens.
CONCLUSIONS
Results show that densification process of European beech wood (Fagus sylvatica) is
significantly influenced by the direction of thick rays and growth rings. The most uniform
densification was in nearly tangential direction. Also expansion of a specimen in the direction
perpendicular to applied force was the lowest for the tangential compression. Radial
compression of thick material is not recommended because of significant influence of thick
rays on product quality.
Ammonia plasticization effect at 0.2 MPa gas pressure reduces the compression force
significantly and it is sufficient for densification. Compared to hot steam, it was less efficient.
On the other hand, ammonia gas plasticization works fast at a normal temperature and low
moisture content.
REFERENCES
[1] Inoue M, Norimoto M, Tanahashi M, Rowell MR (1993) Steam or heat fixationof
compressedwood.Wood and Fiber Science, 25(3):224–235
[2] Kamke FA, Sizemore H(2005) Viscoelastic thermal compression of wood. U.S. Patent No.
US2005/0006004A1,<http://www.freepatentsonline.com/20050006004.pdf>
[3] Navi P, Sandberg D (2012) Thermo-hydro-mechanical wood processing. CRC Press, Boca
Raton
[4] Stojčev A, Kleparník V, Černý R, Valášek V, Chadžiev N (1979) Lignamon – zušlech-těné
dřevo, výroba, vlastnosti a použití (Lignamon – improved wood, production, pro-perties and
utilization). SNTL, Praha
[5] Trebula P (1996) Sušenie a hydrotermická úprava dreva (Drying and hydro-thermal treatment
of wood). Technická univerzita vo Zvolene, Zvolen
[6] Vaněk J (1952) Ohýbaný nábytek (Bent wood furniture). Průmyslové vydavatelství, Praha
27
SELECTED PHYSICAL PROPERTIES OF VISCOELASTIC THERMAL
COMPRESSED WOOD FROM FAST GROWING POPLAR
S. Horníček1,*, P. Rademacher1, A. Kutnar2, F. A. Kamke3, R. Rousek1
1
2
Mendel University in Brno, Faculty of Forestry and Wood Technology, Department of Wood Science,
*
University of Primorska, Andrej Marušič Institute, Muzejski trg 2, SI-6000 Koper, Slovenia; University of
Primorska, Faculty of Mathematics, Natural Sciences and Information Technology,
Glagoljaška 8, 6000-Koper, Slovenia
3
Oregon State University, Department of Wood Science and Engineering
119 Richardson Hall, Corvallis, OR, USA
INTRODUCTION
Densification of wood has been known for several decades; the first patent appeared at the
beginning of the 20th century [1]. Nowadays, it is combined with other treatment processes to
improve additional wood properties. An innovative example of this combination is the
viscoelastic thermal compression (VTC) process.
The VTC process was developed to improve the properties of wood and combines several
procedures in rapid and continuous treatment of thin lamina. This process uses a combination
of steam, heat, and mechanical compression [2, 3].
In this study, material of poplar wood from fast growing short rotation plantation (SRP),
modified by VTC process, was used for investigation and results were compared with nonmodified native wood of plantation grown poplar. Selected physical properties, i.e., density,
equilibrium moisture content (EMC), and modulus of elasticity (MOE) were investigated.
The material used for investigation was plantation grown poplar clone Max-4 (Populus
nigra x Populus maximowiczii) from the Czech Republic. Samples were prepared from split
and debarked logs, stored under room conditions. Dimensions of samples were 4x70x550 mm3
(RxTxL) for the first group (VTC1) and 6x90x550 mm3 for the second group (VTC2), 12
pieces per group. The samples were conditioned before treatment in a conditioning chamber
with air humidity of 65% and a temperature of 20 °C.
The process of VTC was carried out in a pressurized vessel equipped with a heated
hydraulic press [4]. Temperature during compression was 170 °C for 2.5 minutes, which was
increased to 200 °C for 4 minutes. Compression ratio depended on the group. The first group
(VTC1) was compressed from an initial thickness of 4 mm to 2 mm, in the second group
(VTC2) thickness change was from 6 mm to 2 mm. After cooling the samples were
conditioned in a conditioning chamber with 65% air humidity and a temperature of 20 °C.
Measurements of physical and mechanical properties were carried out by non-destructive
methods; each treatment group consisted of 12 replications of original size (see above),
including all knots and other failures in order to show semi-practical material quality for future
utilization. EMC (EN 13183-1) and MOE (Fakopp 2D ultrasonic timer) were measured after
conditioning of all samples in 65% air humidity and 20 °C compared to dried samples in
103 °C (density [ρ0]). MOE was measured in several areas without knots and other failures by
28
means of each of 12 full size samples per treatment, using a distance of 100 mm between
source and target sensors and fitting to the gap between knots and other failures.
RESULTS
Density ratios after compression of materials were 1 : 2.3 : 2.9. Significant decrement of
EMC was observed in the case of both treated materials (Fig. 1), showing similar behavior for
both densification ratios. The same improvement is visible (Fig. 1) in the case of MOE with
three times higher values of both compressed materials compared to control. Higher densities
of materials – native as well as compressed – result usually in higher mechanical properties.
Due to high variability of MOE for semi-practical sized samples no differences could be
determined in this study between varied intensities of densification.
Figure 1: Selected physical properties of density [ρ0], EMC65%, and MOE65%.
CONCLUSIONS
Results show that compression and heat treatment in the viscoelastic thermal compression
process lead to significant changes in physical and mechanical properties of the treated
material.
The density of material depends on the degree of densification and has a crucial effect on
properties. This effect is visible in the case of EMC and MOE (Fig. 1). The goal of this study
was to examine the improvement of properties of SRP poplar clone after applying the VTC
densification process.
Property improvement of plantation grown poplar wood has a huge potential for future use
of this low-cost and fast-growing material, which would save high value materials for special
uses.
REFERENCES
[1] Kollmann FP, Kuenzi EW, Stamm AJ (1975) Principles of Wood Science and Technology.
Vol. II: Wood Based Materials. Springer, Heidelberg
[2] Navi P, Girardet F (2000) Effects of Thermo-Hydro-Mechanical treatment on the structure and
properties of wood. Holzforschung 54(3):287–293
[3] Kamke FA, Sizemore H (2008) Viscoelastic thermal compression of wood. U.S. Patent
Application No. US Patent No. 7.404.422
[4] Kutnar A, Kamke FA, Sernek M (2008) Density and morphology of viscoelastic thermal
compressed (VTC) wood. Wood Sci. Technol. 43(1):57–68
29
THE NUMERICAL ASSESSMENT OF A FULL-SCALE TRUSS
RECONSTRUCTED EMPLOYING A TRADITIONAL ALL-WOODEN
JOINTS
J. Milch1,*, J. Tippner1, V. Sebera1, J. Kunecký2, M. Kloiber2, M. Navrátil2
1
Zěmědělská 3, 613 00 Brno, Czech Republic
*
2
The Institute of Theoretical and Applied Mechanics AS CR, v. v. i.
Prosecká 76, 19000, Prague, Czech Republic
INTRODUCTION
The assessment of mechanical behaviour of all-wooden joints used in historical timber
structures such as churches, castles etc. is currently paid a big attention in the Czech Republic,
and Central Europe as a whole. The reasons are (a) a high number of such structures; (b) their
significance to the national cultural heritage and maintenance for preserving their cultural
value; and (c) missing information about global mechanical behaviour of joints and whole truss
structures when loaded. Generally, valuable historical monuments need to be evaluated as
regards the structure and safety of all timber elements in the structure for their future
preservation [1].
The present paper shows a novel methodology for virtual assessment of mechanical
behaviour used in a historically valuable gothic truss structure of St. James's Church in Brno,
which is very valuable from both structural and architectural points of view. The church was
constructed between1220 and 1724, the used styles including the Romanesque, the Gothic and
the Neogothic. Also carpentry master Anton Ebenberger participated [2]. The aim of this paper
was to describe the real loading of a joint that corresponds to the real function of a joint in the
truss structure during the loading owing to new positions of replacement joints in the truss.
Currently, the truss of St. James’s church shows large defects including decayed members;
therefore, renovation is needed. The restoration of the truss should be carefully implemented in
the structure and analyzed beforehand. Therefore, the numerical approaches based on FEM
were used to evaluate the mechanical behaviour of the beam truss with a detailed 3D solid
joint.
The numerical finite-element 3D model of the truss structure was virtually assessed and
parametrically built in ANSYS computational system using the Ansys Parametric Design
Language (APDL, v.14.5). The truss structure geometry of the central nave consists of 52 frames
of two kinds, full frames and common ones amongst them. Total length of the nave is approx. 77
m, width span is approx. 23 m; the truss is placed at four supports; height of truss is approx. 14.8 m
with 52° slope. The model of 3D beam structure was created by meshing of lines with the
BEAM189 finite element. The connections between the beams are assumed as “semi-rigid” and
modeled with a technique called constraint equations (CE). CE allows defining simple linear
relationships of degrees of freedom (DOF's) between groups of selected nodes of both connected
beams. The displacements and rotations of the first beam in the joint are scaled by linear factor and
then applied to the second beam. Several alternatives of different rigidity of joints were computed;
factors for displacements and rotations 1.0 (fully rigid), 0.8, 0.5 and 0.2 were used. The model of
30
full frame consists of 234 beams and 68 joints, model of each common frame consists of 61 beams
and 19 joints. The frames are connected by longitudinal purlins (21 in total connected via 63
joints). The longitudinal stiffness of the whole truss is achieved using longitudinal purlins and
Andrew's crosses. The 3D beam model of truss consists of approx. 3,170 FE’s. The total count
of CE’s is 438. The 3D sub-model of joint implemented at different positions into truss consists of
approx. 59,000 to 75,000 solid FE’s and with approx. 5 000 contact-target elements. The total
count of FE’s corresponds to the total length of the replaced beam.
The load of the truss was applied according to standards EN 1991-1-1, EN 1991-1-3, EN 19911-4. The truss structure was loaded using a combination of applied loads: self-weight, cladding,
snow and wind load by the location of St. James's Church in Brno, Czech Republic.
The principle of sub-structuring was used to allow detailed 3D solid & contact modeling of the
wooden joint with corresponding loading coming from simplified 3D beam structure of the whole
truss. The 3D solid joint was inserted into the truss using a contact pair with a “master node”.
Material model of 3D beam structure and detailed 3D solid model of joint assumes the elastic and
fully orthotropic properties of Norway spruce (Picea abies L.).
Table 1: Elastic and fully orthotropic material model for Norway spruce used in FE computation. ρ: density; EL/ER/ET:
normal elastic moduli; GLR/GLT/GRT: shear moduli; νLR/νLT/νRT: Poisson’s ratios.
Species
ρ
EL
ER
ET
GLR
GLT
GRT
νLR
νLT
νRT
Norway spruce
420
13.650
0.789
0.289
0.573
0.474
0.053
0.023
0.014
0.557
EL, ER, ET and GLR, GLT, GRT are in (MPa); νLR, νLT, νRT are in (-); ρ are in (kg∙m-3)
RESULTS, DISCUSION AND CONCLUSIONS
The 3D finite element analysis was used to predict the mechanical behaviour of a truss
structure. Further, the detailed 3D solid joints were implemented and computed at different
positions in the truss in order to determine the mechanical response of replaced joints during
the load from restoration. Results showed very good design of the assessed truss in the global
mechanical behaviour while the rigidity of joints varied in the longitudinal and transverse
directions of frames. Changes in global truss behaviour were found, but the changes in the
objective vertical displacement are not high. The differences depending on rigidity level
(factors) were not more than 7% in maximum vertical displacement of beams. Each member of
the truss has an appropriate structural function in the global truss rigidity and stability. Minor
differences were also recognized in the global truss behaviour owing to new positions of
implemented replaced joints in the truss (i.e., emphasis should be placed on correct orientation
of replaced joints). This supports the idea that each connection should be adapted to the
particular conditions in the truss structure or restoration.
ACKNOWLEDGEMENTS
This paper was funded by the grant no. 49/2014 of Internal Grant Agency of Faculty of
Forestry and Wood Technology at Mendel University in Brno and Ministry of Education,
Youth and Sports of the Czech Republic (grant no. 6215648902) and by the project NAKI
“Design and Assessment of Timber Joints of Historical Structures” reg. No,
DF12P01OVV004, provided by the Ministry of Culture of the Czech Republic.
REFERENCES
[1] Abruzzese D, Miccoli L, Yuan J (2009) Mechanical behavior of leaning masonry Huzhu
Pagoda, J Cult Herit 10:480-486. doi:10.1016/j.culher.2009.02.004
[2] Navrátil M (2013) Průvodní zpráva k technologickým postupům oprav a sanace
poškozenýchdřevěných částí krovu, Brno (in Czech)
31
Session II
Lignocellulosic Material Science
LOCALIZATION OF LIGNIN AND PHENOLIC COMPOUNDS IN
WOODY TISSUE BY MEANS OF SCANNING UVMICROSPECTROPHOTOMETRY
G. Koch & U. Schmitt*
Thünen Institute of Wood Research
Leuschnerstr. 91, 21031 Hamburg, Germany
*
INTRODUCTION
Cellular UV-microspectrophotometry is an established technique for characterizing lignin in
situ and for its semi-quantitative determination in the various layers of woody cell walls. The
technique is based on the ultraviolet illumination of semi-thin transverse sections. Lignin
displays a characteristic UV-absorbance spectrum with maxima around 212 nm and 280 nm
due to the presence of associated phenylpropane groups with several chromophoric structural
elements. No other component in the mature wood cell wall shows UV-absorbance properties
in the same spectral region. Furthermore, the intensity of absorbance can be related to the
concentration of lignin across the cell wall.The UV-absorbance maximum is sensitive to
structural differences of the lignin allowing discrimination between hard- and softwood lignins
due to different ratios of their guaiacyl- and syringylpropane units. Softwood lignin is mainly
composed of guaiacylpropane units with an absorbance maximum at 280nm, whereas
hardwood lignin consists of guaiacyl- and syringylpropane units in varying ratios characterized
by a shifted maximum between 270–278nm. Two analyzing modes are possible using the UVspectroscope, i.e., point and scanning analyses. Point analyses are carried out with varying
wavelengths, for scanning analyses a constant wavelength is used.
RESULTS
Occurrence and distribution of lignin and phenolic compounds in woody tissue can be
determined on a cellular level by scanning UV microspectrophotometry (UMSP). This
improved analytical technique enables the localization of aromatic compounds within
individual cell wall layers [1]. The technique is based on the absorbance of UV radiation in
semi-thin transverse sections of woody tissue. Besides the localization, also concentration of
lignin within cell wall layers and phenolic compounds in walls or lumens can be determined
semiquantitatively. Furthermore, the shift of the UV-absorbance maximum indicates structural
differences of the lignin allowing discrimination between natural and modified lignin structures
due to their different absorbance behaviour. For demonstration, untreated as well as thermally
and chemically modified wood samples of 1 µm thickness were scanned at a defined
wavelength of 280 / 278 nm and evaluated with the scan program APAMOS® (AutomaticPhotometric-Analysis of Microscopic Objects by Scanning). This software digitizes
rectangular fields with a local geometrical resolution of 0.25x0.25 µm2 and a photometrical
resolution of 4096 grey scale levels which are converted into 14 basic colours to visualize the
absorbance intensities. The scans can be depicted as two- or three-dimensional image profiles
including a statistical evaluation (histogram) of the semiquantitative lignin distribution.
33
Several examples on lignin localization in developing wood tissue, in modified wood
and pulp fibres are presented to demonstrate the power of the technique. Fig. 1 shows scanning
micrographs of normal and compression wood tracheids with the distinctly higher lignin
content in compression wood.
Figure 1: Topochemical detection of lignin in spruce tracheids (Picea abies L.) by scanning UV-spectrophotometry:
Compression wood tracheids (right) with much higher lignin content than tracheids in normal wood (left).
CONCLUSIONS
Scanning UV-microspectrophotometry was found to be ideally suited for the determination
of lignin on a cellular level in differentiating and mature woody tissue as well as in wood
products. The high resolution enables clear differentiation between varying lignin contents in
the different wall layers. The preparation of woody material with embedding in epoxy resins
does not affect the lignin distribution because no dehydrating solvents are applied during
processing.
REFERENCES
[1] Koch G, Kleist G (2001) Application of scanning UV microspectrophotometry to localize
lignins and phenolic extractives in plant cell walls. Holzforschung 55:563-567
[2] Koch G, Schmitt U (2013) Topochemical and electron microscopic analyses on the lignification
of individual cell wall layers during wood formation and secondary changes. In: Fromm J (ed)
Cellular Aspects of Wood Formation, Plant Cell Monographs 20. Springer, Berlin Heidelberg,
41-69
34
ENVIRONMENTALLY FRIENDLY MATERIALS FOR WOODBASEDCOMPOSITES: HEAT-TREATED WOOD, LIQUEFIED WOOD
AND TANNIN FOAMS
M. Sernek*, M. Kariž, M.Kutek Kuzman, M. Čop
University of Ljubljana, Biotechnical Faculty,Department of Wood Science and Technology
Jamnikarjeva 101, SI-1000 Ljubljana, Slovenia
*
INTRODUCTION
Wood and bark are two common natural renewable resources that can be most easily used
for creating bio-based polymers and composites. New processing technologies for this natural
and renewable materials have been developed, which increased the variety of possible
applications. This paper describes three recently developed processes and products, which can
be used for manufacturing of environmentally friendly composites: (1) heat-treated wood, (2)
liquefied wood and (3) tannin foams.
BONDING OF HEAT-TREATED WOOD
The heat treatment of wood at elevated temperatures ranging from 160 to 260 °C improves
dimensional stability and biological durability of wood. This process represents an attractive
"non-biocidal" alternative to traditional preservation treatments, and broadens the use of less
durable wood species. Several studies have shown that heat-treated wood can be sufficiently
bonded with most of industrial wood adhesives, but usually some modifications of bonding
process and/or adhesive need to be made [1]. It was determined that the shear strength of the
dry adhesive bonds decreased with a higher degree of thermal modification. However, this
decrease was more pronounced for PVAc adhesive bonds than for MUF and PUR adhesive
bonds. After soaking in water the shear strength of the MUF and PUR adhesive bonds dropped
to half the initial dry strength, whereas in the case of PVAc reduction of adhesive bonds
strength was higher. The delamination with PUR and MUF adhesive was small and met the
standard requirements, but the PVAc adhesive bonds exhibit high delamination [2].
BONDING WITH LIQUEFIED WOOD
Liquefied wood is a product of a liquefaction process in which wood particles (wood
residues) are dissolved in organic solvents, with or without a catalyst, at moderate temperatures
(100–250 °C). During liquefaction the basic wood components are degraded into oligomers or
monomers. Liquefied wood has the potential to be used for bonding of wood. One of
disadvantages of adhesives made from liquefied wood is low shear strength of the adhesive
bond. This shortcoming can be resolved in different ways: with addition of synthetic resin or
by optimizing the pressing parameters [3]. It was found that a press temperature of 180 °C
(Figure 1) and a pressing time of 12 minutes were determined to be optimal for bonding of the
5 mm thick beech wood lamellas with liquefied wood. However, the shear strength was too
low (6–7 N/mm2) to attain the standard requirements. Despite this, wood failure of the bond
was high (90–100%).
35
Figure 1: The influence of press temperature on the bond performance of specimens bonded with liquefied wood.
TANNIN-BASED FOAMS
Bark is less attractive for commercial use and is typically a waste product that is used for
burning. It contains natural protective compounds called tannins, which are also suitable for the
production of foams. The resulting thermosetting material can be used as a thermal or sound
insulator. The results showed that the curing process was delayed when the proportion of
glycerol or tannin in the mixture was increased, but for the catalyst, it was observed that an
optimum amount existed [4].
ACKNOWLEDGMENT
This research was performed within the research project J4-2177 and framework of the
BIOFOAMBARK project. The study was funded by the WoodWisdom-ERA Net Research
Program, which is a trans-national R&D program jointly funded by national funding
organisations within the framework of the ERA-NET project WoodWisdom-Net 2. The
research was also funded by the Slovenian Ministry of Education, Science, and Sport. Also, the
authors gratefully acknowledge the financial support by the Slovenian Research Agency.
REFERENCES
[1] Hill CAS (2006) Wood modification. Chemical, thermal and other processes. John Wiley& Sons,
Chichester
[2] Kariž M (2011) Vpliv termične modifikacije lesa na utrjevanje lepil in kakovost lepilnih slojev.
PhD Thesis, University of Ljubljana
[3] Ugovšek A, Sernek M (2013) Effect of pressing parameters on the shear strength of beech
specimens bonded with low solvent liquefied wood. J Adh Sci Tech 27(2):182-195
[4] Čop M, Laborie MP, Pizzi A, Sernek M (2014) Curing characterisation of spruce tannin-based
foams using the advanced isoconversional method. Bioresources 9(3):643-4655
36
SUPERCRITICAL CARBON DIOXIDE EXTRACTION OF VALUEADDED CHEMICALS FROM SLOW PYROLYSIS LIQUIDS
Y. Feng1,* & D. Meier2
1
University of Hamburg
*
2
INTRODUCTION
Facing the depletion of fossil energy resources, as well as economic and environmental
issues, alternative energy sources need to be developed to substitute the traditional fossil
sources such as coal, petroleum and natural gas [1]. Biomass, an abundant renewable and
sustainable material, has been widely studied as a new energy carrier. Thermochemical
conversion processes such as fast pyrolysis convert biomass predominately into liquids, the socalled bio-oil with a yield of approximately 75 wt% (incl. 25 wt% water) [2]. Bio-oil may be
further upgraded into transportation fuels through various catalytic hydrotreating methods [3].
Apart from the fuels, bio-oil could provide value-added or platform chemicals, which is a great
advantage over other new energy sources (wind, solar). Materials derived from bio-oil could be
used in adhesives, bitumen, preservatives, etc [4]. Since bio-oil is a complex mixture of
chemical components, it needs separation or extraction before further application [5].
Extraction with supercritical carbon dioxide (scCO2) – a promising green solvent – has several
advantages such as high solubility at low temperature, adjustable selectivity by changing the
process conditions and no solvent residue in the extract.
Table 1: Elemental analysis, higher heating value (HHV), water content of slow pyrolysis liquids, extracts and residues
on dry basis.
Sample
C (wt%)
H (wt%)
O* (wt%)
HHV (MJ kg-1)
H2O (wt%)
SP
SP-15 extr.
60.02
59.15
6.87
7.23
33.11
33.62
24.24
24.37
1.13
0.83
SP-20 extr.
58.70
7.21
34.09
24.11
1.19
SP-25 extr.
59.35
7.18
33.48
24.39
1.61
SP-15 res.
61.80
6.68
31.52
24.86
1.28
SP-20 res.
61.98
6.69
31.33
24.97
0.84
SP-25 res.
62.54
6.66
30.79
25.21
1.51
*calculated by difference
SP: slow pyrolysis liquids; -15, -20, -25: pressure in MPa.
RESULTS
Pyrolysis liquids used in the experiments are dark brown with pungent odor and contain
very litter water (less than 2 wt%) due to pretreatment. The scCO2 extracts after extraction are
transparent reddish liquids with a stronger odor and much lower viscosity, leaving high
37
molecular compounds in the residue. The extracts could not be dissolved in water. No more
pyrolytic lignin (water-insoluble material) exists in extracts. Extraction yield could reach more
than 50 wt% which is dependent on the CO2 flow rate and pressure. After scCO2 extraction,
only slight changes of elemental composition are noticed. Consequently, the change of the
heating value is not obvious (see Table 1).
Figure 1: Successive scCO2 extraction.
Figure 2: Fixed pressure scCO2 extraction.
For gas chromatography (GC) detectable components, which mainly include acids, esters,
ketones, furans, phenols, guaiacols and syringols, are effectively enriched in the extracts.
However, the carbohydrates such as levoglucosan could not be extracted by scCO2 but are left
in the residue. The compositional analysis of both successive extractions (150-250 bar) and
fixed pressure extraction (100, 200, 250 bar) shows that the scCO2 extraction pressure between
150 and 250 bar does not influence the chemical substances significantly. Future work should
be focused on the selectivity improvement using different adsorbents and adding modifiers.
CONCLUSIONS
From the different extraction methods applied in the pyrolysis liquids, scCO2 proves to be a
promising one while high value-added chemicals could be selectively enriched in the scCO2
extracts, leaving the high molecular compounds in the residue. The quality of the extract is also
greatly improved in comparison with the crude pyrolysis liquids.
ACKNOWLEDGEMENT
The authors would like to thank China Scholarship Council (CSC) forfinancial support (File
No. 201206510004).
REFERENCES
[1] Huber GW, Iborra S, and Corma A (2006) Synthesis of transportation fuels from biomass:
Chemistry, catalysts, and engineering.Chem Rev 106(9):4044-4098
[2] Bridgwater AV, Meier D, Radlein D (1999) An overview of fast pyrolysis of biomass. Org
Geochem 30(12):1479-1493
[3] Elliott DC (2013) Transportation fuels from biomass via fast pyrolysis and
hydroprocessing.Wires Energy Environ 2(5):525-533
[4] Meier D, Faix O (1999) State of the art of applied fast pyrolysis of lignocellulosic materials - a
review. Bioresource Technol 68(1):71-77
[5] Mohan D, Pittman CU, Steele PH (22006) Pyrolysis of wood/biomass for bio-oil: A critical
review.Energ Fuel 20(3):848-889
38
NUMERICAL ANALYSIS OF TEMPERATURE FIELD IN WOOD
DURING THERMAL TREATMENT
M. Trcala
Mendel University, Faculty of Forestry and Wood Technology, Department of Wood Science
INTRODUCTION
Numerical analysis of temperature field during thermal modification of wood was carried
out. The numerical solution – based on finite element method, FEM – of the 3D problem of
transient nonlinear heat transfer in wood is presented. The numerical model was enhanced for
describing chemical reactions of cellulose, hemicelluloses and lignin (pyrolysis model), which
takes into account the exothermic reactions as an internal source of heat energy in a partial
differential equation describing heat transfer in wood. The influence of sample dimensions
(sample geometry) and wood species was studied. The influence of wood species on heating
time to reach the highest temperaturewas negligible. As expected, the sample size played an
important role in the heating duration and in terms of the exothermic reactions of wood (in the
range of higher temperatures).
MODEL
The mathematical model used in the present work is formed by a partial differential
equation for temperature field.
C
T
   λT  f  0
t
(1)
where T is the temperature (K), λ is the matrix of thermal conductivity coefficients of wood
(W.m-1.K-1), C is the specific heat of heat (J.kg-1.K-1), ρ is the wood density (kg.m-3), f is heat
of pyrolysis (W.m-3).
The term f within equation (1) represents the internal source of heat energy generated as a
result of the chemical reaction of the constituents of the wood cell wall during thermal
modification[1, 2].
f  h1k1 H  h2k2  S1   h3k3  h4k4  C  h5k5 L
(2)
where hi is the enthalpy of reaction i, ki is the reaction rates of wood compounds, ρH, S1, L is the
density of hemicellulose, lignin and coal or tar.
Then it is possible to deduce the system of ordinary differential equations describing
degradation of the wood components, hemicelluloses, cellulose and lignin, respectively:
d G
d S
d H
 k1 H
 0.43k1 H
 k2  S  0.57k1 H
dt
; dt
; dt
;
1
1
1
39
d G2
dt
 0.56k2  S1
d  S2
;
dt
 0.44k2  S1
(3)
where ρH represents the mass of hemicellulose; k1 and k2 are the reaction rates for
hemicellulose; and ρSi , ρGi are, respectively, the masses of the coal or tar and volatile matters
produced during reaction i = 1, 2.
d G
d C
   k3  k 4   C
 k4  C
dt
; dt
4
(4)
where ρC is the mass of cellulose and k3 and k4 are the reaction rates for cellulose.
d G
d L
  k5  L
  k5  L
dt
; dt
5
(5)
where ρL is the mass of lignin and k5 is the reaction rate for lignin.
RESULTS
Figure 1: Experimental and numerical course of temperature in the core of sample
CONCLUSIONS
Finite element analysis of the temperature field during thermal modification of wood was
performed. The numerical results have been compared with experimental measurements and
are generally in good agreement. The results could be improved by a more exact consideration
of wood components for each type and wood species and more accurate conditions in the
pyrolysis model.
REFERENCES
[1] Turner I, Rousset P, Rémond R, Perré P (2010) An experimental and theoretical investigation
of the thermal treatment of wood (Fagus silvatica L.) in the range 200-260°C. Int J Heat Mass
Transfer 53:715-725
[2] Perré P, Rémond R, Turner, I (2013) A comprehensive dual-scale wood torrefaction model:
Application to the analysis of thermal run-away in industrial heat treatment processes. Int J
Heat Mass Transfer 64:838-849
40
ANTIOXIDANT ASSAY AS A POTENTIAL ASSESSMENT OF
WOOD EXTRACTIVES ANTIFUNGAL ACTIVITY
P. Sáblík1,*, E. Nebehaj2, P. Rademacher1, T. Hofmann2
1
Mendel University in Brno, Faculty of Forestry and Wood Technology, Department of Wood Science
*
2
University of West Hungary, Institute of Chemistry
Ady Endreu. 5, 9400 Sopron, Hungary
INTRODUCTION
Research studies described defense mechanisms of plants. Tree builds defense against stress
or disease in several ways, physical or chemical. The chemical composition of a tree is
considered one of its main defense system [1]. Wood and plant extracts have been proven to
have antifungal and insecticide properties.
Heartwood extracts from a wide range of plant and tree species show activity against fungi
and insects and many of them can potentially serve as wood protective agents alone or in
combination [2]. Extracts from heartwood of Gmelina arborea were positively tested for their
antifungal activity against basidiomycetes [3] [4]. Recent research has shown that a great
number of plants contain chemical compounds exhibiting bioactivity such as antioxidant and
antimicrobial properties [5, 6].
Interest in active oxygen species has grown with experimental evidence that free radicals
play important roles in a variety of pathological conditions such as ischemiareperfusion,
autoimmune diseases, cardiovascular diseases, cancer initiation, and aging processes [7]. As a
consequence, antioxidative materials are now thought to be prospective protective agents also
against wood degrading organisms. Although natural antioxidants such as a-tocopherols and Lascorbic acid are widely used, investigations are being carried out to discover more potent,
safer antioxidants [8].
When a tropical tree is cut down, only 40% of the tree is used as timber, the rest (sawdust,
bark, etc.) is most often not valued, discarded or used as firewood [9]. Waste recovery is a
challenge increasingly important for industrial processes economically sustainable and
environmental. This volume of wood based material, now being usually combusted for energy
[10], could provide components suitable for upgrading to higher value products like the
suggested wood protective agents.
Aims of this research were to find a relation between the antioxidant activity of extracts and
increasing durability after their impregnation into low durable wood species;and to determine
dependency between single phenolic compounds and an increasing ratio of these compounds in
the extract to antioxidant capacity of agent. This research should lay the foundations of future
industrial usage of waste wood soluble compounds and its rapid evaluation.
Air dried heartwood of African padauk (Pterocarpus soyauxii Taub.) and black locust
(Robinia pseudoacacia L.) and barkof black locust and European beech (Fagus sylvatica L.) were
used for extraction. 10.0 ±0.1g of material, separated with sifting on a 50-mesh was usedfor the
extraction with fexIKA apparatus. Because of the polar aspect of phenolic compounds, water with
high polarity index 10.2 was used. There could be lot of other nonpolar compounds, therefore also
41
methanol (polarity index 5.1) was added into investigation.After extraction process, samples were
evaporated using a rotary evaporator. After evaporation, samples were used for AO assay, HPLC
analysis and impregnation. AO assay was carried out with a spectrophotometer based on FRAP
methodology.The miniaturised wood-block test was used for extract efficiency evaluation against
wood-rotting fungi. The methodology is based on EN 113. It employed wood blocks with a length
of 30 mm and a cross section of 10*5 mm2 prepared from European beech and Scots pine (Pinus
sylvestris L.). Wood used for the experiment has to be without cracks, coloration, rot, insect
damage or any other visible defects.The samples impregnation was conducted in compliance with
EN 113. A specific process of impregnation was chosen for each group, based on vacuum phase
only, without any overpressure phase. Impregnated samples were placed into the conditioning
chamber with a temperature of 22 °C and 60% of relative humidity.Impregnated and nonimpregnated wood samples were sterilized by gamma radiation (28 kGy) and put into Petri dishes
with agar soil covered by fungi culture. Two treated and one reference untreated sample were
placed into each Petri dish on a stainless mesh. Petri dishes were stored in the climate box for 6
weeks at a temperature of 22 °C and 65% of relative humidity. After this time, the samples were
carefully cleaned and dried at 103 °C and the mass loss was calculated for each sample.
RESULTS
Results proved that there is dependency between extractives concentration and
antioxidant activity. Data obtained from rapid durability test also demonstrated activity of
extracts against wood degrading fungi.
ACKNOWLEDGEMENTS
Supported by the European Social Fund and the state budget of the Czech Republic, project
"The Establishment of an International Research Team for the Development of New Woodbased Materials" reg. no. CZ.1.07/2.3.00/20.0269.
REFERENCES
[1] Novriyanti E, Santosa E, Syafii W, Turjaman M, Sitepu IR (2010) Antifungal activity of wood
extract against agarwood-inducting fungi. Journal of Forestry Research Vol. 7 No. 2, 2010: 164
155-165
[2] Sen S, Tascioglu C, Tirak K (2009) Fixation, leachibiliy and decay resistance of wood treated
with some commercial extracts and wood preservative salts. Int Biodeterior Biodegrad
[3] Kawamura F, Ohara S (2005) Antifungal activity of iridoid glycosides from the heartwood of
Gmelina arborea. Holzforschung
[4] Kawamura F, Ohara S, Nishida A (2004) Antifungal activity of constituents from heartwood of
Gmelina arborea. Part 1. Sensitive antifungal assay against basidiomycetes. Holzforschung
[5] Nakano H, Nakajima E, Hiradate S, Fujii Y, Yamada K, Shigemori H, Hasegawa K (2004)
Growth inhibitory alkaloids from Mesquite (Prosopis juliflora) leaves. Phytochemistry
[6] Miliauskas G, Venskutonis PR, Van Beek TA (2004) Screening of radical scavenging activity
of some medicinal and aromatic plant extracts. Food Chem 85:261–237
[7] Springfi eld EP, Amabeoku G, Weitz F, Mabusela W, Johnson Q (2003) An assessment of two
carpobrotus species extracts as potential antimicrobial agent. Phytomedicine 10:434–439
[8] Cerutti PA (1985) Prooxidant states and tumor promotion. Science 227:375-381
[9] Shimizu K, Kondo R, Sakai K (2002) Antioxidant activity of heartwood extracts of Papua New
Guinean woods. J Wood Sci 48:446-450
[10] Kemppainena K, Siika-ahoa M, Pattathilb S, Giovandoc S, Kruusa K (2002) Spruce bark as
an industrial source of condensed tannins andnon-cellulosic sugars. Industrial Crops and
Products 52 158– 168
42
USING SUPERCRITICAL CARBON DIOXIDE AS ANTISOLVENT FOR
WOOD MODIFICATION: PRELIMINARY STUDIES
P.K. Mishra1,2,3,*, E. Cabane2,3, R. Wimmer1, I. Burgert2,3
1
Zemědělská 3, 613 00 Brno, Czech Republic
*
e-mail: [email protected], [email protected]
2
3
ETH Zurich, Institute for Building Materials, Zurich, Switzerland
Empa – Swiss Federal Laboratories for Material Testing and Research, Applied Wood Research
Laboratory, Dübendorf, Switzerland
INTRODUCTION
Supercritical carbon dioxide (scCO2) has been widely studied as a solvent for wood
modification purposes due to its favorable properties of zero surface tension, greener nature,
high diffusivity and tunable solubility by adjusting temperature and pressure [1]. The major
drawback comes from the limited solubility of modification agents, which can be addressed by
using a co-solvent or by utilizing scCO2 as an anti-solvent [2]. Using scCO2 as an anti-solvent
requires the dissolution of a compound in an expandable solvent (i.e. scCO2 is miscible in
solvent but does not dissolve the solute). There is a wide range of scCO2 expandable solvents
which can dissolve theoretically any compound. Another advantage of using scCO2 as antisolvent is the possibility to precipitate the solute and the easy recollection of solvent during the
process.
Dioxane soluble fraction of kraft lignin (Sigma Aldrich) was used as impregnation material
and called D-lignin in this work. A 1.8% (w/v) solution of D-lignin in Dioxane was vacuum
impregnated in previously dried (65 °C, 48 hours in vacuum oven) spruce wood cubes
(10×10×10 mm3) for 48 hrs. These cubes were transferred to supercritical CO2 reactor and
processed for 6 hrs. Collected cubes from previous steps were weighed and placed in vacuum
oven at 65 °Cfor overnight drying and weighed again. Two controls with solvent only
impregnation(con.2) and no impregnation(con.1) were also considered.For water absorption
test con.2 was considered as control. Samples were characterized using optical microscopy and
water absorption (percentage weight gain with time) for 8 hours.
RESULTS
Controls without any impregnation showed a before drying (BD) weight gain of 5–6 %.
That means BD weight gain (figure 1) for every sample has a 5–6 % contribution of residual
CO2 at the time of weight measurement. This observation also gives an idea of the actual
amount of solvent present in the samples. In optical microscopic evaluation of samples,
presence of lignin can be clearly seen on lumen-cell wall interface (figure 2). The water
absorption test done for 8 hours (preliminary)shows a clear decrease in water absorption
(percentage weight gain with time) due to lignin impregnation. With weight gain of 7–8%, a
very thin layer of lignin on cell wall lumen interface can be observed in figure 2, which can be
seen as a prime source of hydrophobicity improvement due to the hydrophobic nature of Dlignin. Utilization of scCO2 and this technique brings some advantages over classical methods
43
such as: 1)solvent recollection (major proportion) during processing. 2) Possibility of
functional biomaterial impregnation, since the temperature does not go beyond 65 °C.
Utilizing ScCO2 as anti-solvent serves as a tool to transport temperature sensitive materials in a
fast and efficient way.
25
percentage weigt gain
20
BD= before drying
AD= after drying
15
10
5
0
Lig. BD
-5
Lig.AD con.1BD con.1 AD con.2 BD Con.2
AD
Figure 1.Weight gain for different samples and controls.
Figure 2.Optical microscopy of samples and arrow mark thin layer of deposited lignin
80
percentage weight gain
70
60
50
40
untreated
30
control
20
lignin
10
0
2hrs
4hrs
6hrs
8hrs
time in hours
Figure 3:Preliminary test on water absorption
44
CONCLUSIONS
 Solubility limitation of CO2 as solvent was successfully addressed, using it as anti-solvent.
ScCo2 insoluble compound was precipitated using it as anti-solvent.
 Location of lignin was observed to be on cell wall–lumen interface.
 Water absorption test shows a clear decrease in water uptake due to treatment.
REFERENCES
[1] Acda MN, Morrell JJ, Levien KL (2001) Supercritical Fluid Impregnation of Selected Wood
Species with Tebuconazole. Wood Sci Technol 35(1-2):127–136. doi:10.1007/s002260100086
[2] Cooper AI (2000) Polymer Synthesis and Processing Using Supercritical Carbon Dioxide.
JourMaterChem 10 (2): 207–234. doi:10.1039/a906486i
45
THERMOPHYSICAL PROPERTIES OF MEDIUM DENSITY
FIBERBOARDS MEASURED BY PULSE TRANSIENT METHOD
E. Troppová* & J. Tippner
*
INTRODUCTION
Medium density fiberboard (MDF) is a widely used composite material made of wood
fibers. Its favorable physical and mechanical properties enable usage mainly in furniture and
construction production. Even though the knowledge of MDF thermal properties is important
in drying and modification processes, there are only few studies available. Different methods
can be used to measure thermal properties. Transient methods, as for example hot strip method
or transient plane source technique, enable measurement of a full set of thermophysical
parameters within a single measurement. The used RT-lab device based on the pulse transient
method allows measurements in various atmosphere types (air or vacuum) in controlled
temperature regimes. The basic principle of the transient technique is based on the generation
of a heat pulse by a planar heat source and on registration of temperature response by a
thermocouple [1]. Investigation of moisture influence on thermal parameters of building
materials was carried out by [2].
Commercially available MDFs with three various thicknesses of 12, 18 and 25 mm were
cut to approximate dimension (width and length) of 100 x 100 mm. All 30 samples (10 samples
of each MDF thickness) were conditioned under 20 °C and a relative humidity of 65% in a
Sanyo MTH 2400 air chamber to reach the equilibrium moisture content. An X-ray
densitometer (X-RAY Dense-Lab, Germany) was used to scan all samples with a scanning step
length of 0.01 mm. An average density profile from each type of sample was established. The
RTB device was used to measure MDF thermal parameters. The measured specimen consists
of three MDF samples where a heat source and a thermocouple are placed between the contact
surfaces. A planar heat source is placed between the first and the second part of the specimen,
while a thermocouple is located between the second and the third part. An electrical current
coming through the metallic foil generates the heat pulse and furthermore the non-stationary
temperature field within the specimen [3]. The temperature response is measured by a
thermocouple. The specific heat, thermal diffusivity and thermal conductivity are calculated
from the parameters of the temperature response (the time and the magnitude of the maximal
temperature increase).
RESULTS
The thermal conductivity, thermal diffusivity and specific heat capacity were derived
from the measurements based on the pulse transient method. Thermal conductivity increases
with an increasing density of samples, as stated by e.g. [4]. The dependence on density was
confirmed by the measured data of MDF samples with thicknesses 12 and 18 mm. The
inaccuracy in data evaluation in the case of MDFs with the thickness of 25 mm is mostly
caused by underestimated parameters influencing the measuring process. [5] published a
46
thermal conductivity value of 0.192 W.m-1.K-1 at 7.2% moisture content and 20 Celsius
degrees for MDF with a density of 640 kg.m-3 measured by the hot-wire method. The thermal
conductivity (0.195 W.m-1.K-1) at 25 Celsius degrees for oven-dried MDF with a density of
765 kg.m-3 established according to the light flash system was published in [6]. Variety of
factors strongly influences the thermal conductivity values (density, moisture content,
temperature, measuring method, technological process, sample preparation), as seen from the
difference between the data available in literature and our measured values. The influence of
some selected parameters on the final thermal properties will be presented at the InWood
conference.
Table 1: Mean thermophysical properties of MDFs.
Thickness
Density
-3
Thermal conductivity
-1
-1
Thermal diffusivity
7
2 -1
Specific heat capacity
[mm]
[kg.m ]
[W.m .K ]
[10 m .s ]
[J.kg-1.K-1]
12
18
25
745.3
764.5
714.4
0.123
0.171
0.287
0.976
1.261
1.505
1625.4
1772.1
2675.0
CONCLUSIONS
Main thermophysical parameters (thermal conductivity, thermal diffusivity, specific heat
capacity) of MDF samples with different thicknesses were measured by the pulse transient
method. Density strongly influences thermal properties. The influence of measuring time, pulse
duration and temperature on the final thermal properties will be later presented.
REFERENCES
[1] Boháč V, Dieška P, Kuničár L (2007) The Heat Loss Effect at the Measurements by Transient
Pulse Method. Measur Sci Rev 7(3):1-4
[2] Boháč V, Kubičár L, Dieška P, Némethy L (2009) Investigation of Moisture Influence on
Thermophysical Parameters of Porfix Aerated Concrete, in Thermophysics 2009, Proc. of the
Meeting of the Thermophysical Society - Working Group of the Slovak Physical Society 13-19
[3] Kubičár L, Boháč V, Vretenár V, Barta Š, Neuer G, Brandt R (2005) Thermophysical
Properties of Heterogeneous Structures Measured by Pulse Transient Method. IntJ Thermophys
26(6):1949-1962
[4] Kühlmann G (1962) Investigation of the Thermal Properties of Wood and Particleboard in
Dependency from Moisture Content and Temperature in Hygroscopic Range. Holz als Rohund Werkstoff 20(7):259-270
[5] Yapici F, Ozcifci A, Nemli G, Gencer A, Kurt S (2011) The Effect of Expanded Perlite on
Thermal Conductivity of Medium Density Fiberboard (MDF) Panel. Technology 14(2):47-51
[6] Zhou J, Zhou H, Hu Ch, Hu S (2013) Measurements of Thermal and Dielectric Properties of
Medium Density Fiberboard with Different Moisture Contents. BioResources 8(3):4185-4192
47
Session II
Lignocellulosic Material Science
Poster Session
ANALYTICAL EQUIPMENT AT MENDEL UNIVERSITY IN BRNO
Z. Paschová* & P. Rademacher
*
INTRODUCTION
In the last year, a new modern analytical laboratory was established at theFaculty of
Forestry and Wood Technologyof the Mendel University in Brno. Laboratory equipment
allows an analysis of a wide range of volatile, semi-volatile and non-volatile organic
compounds in different matrices, complying with specific research demands.
The new laboratory is equipped with the latest technology in the field of chromatography
instrumentation. A combination of gas chromatography and mass spectrometry (GC-MS)
enable to identify unknown volatile substances in complex mixtures, with use of thermal
desorption (TD) to be able to analyse air samples collected in the field; head-space (HS)
analysis enables us to analyse some volatiles directly, without a complicated sample
preparation. The modular system for high performance liquid chromatography (HPLC) with
connection to a diode array detector (DAD) enables sensitive qualitative and quantitative
determination of the range from less volatile to nonvolatile compounds. In the laboratory also
the performance of spectrophotometric determination and all extraction and preparatory works
required for analysis are possible.
EQUIPMENT
Gas chromatography: Modular system from Agilent Technologies, series 7890 for GC and
series 5977 for MS, consistingof gas chromatograph with flame-ionization detector (FID),
autosampler for 150 samples, thermostatted column compartment and MS single quad, was
composed.Another possibility of our modular system is a connection to the thermal desorption
(TD) Markes Unity II with possibility of concentration of samples by cryofocusing and using
of an additional module for Markes Unity TD – so called head-space analysis. Figure 1 shows
complete instrumentation of GC-FID-MS-TD-HS and a sample chromatogram of qualitative
analysis of bio-oil. Dominant peaks in the chromatogram belong to compounds such as
syringol, guaiacol, p-cresol, furfural, acetol acetate, 1-acetoxy-2-butanone, p-ethyl quaiacol or
1,2,4-trimethoxy benzene, partly known as biocides and used in frame of project, for example
in impregnated beech or poplar wood.
Figure 1: GC-MS-FID-TD-HS instrumentation and chromatogram of analysis of pyrolysis bio-oil.
49
High performance liquid chromatography: Modular system from Agilent Technologies,
series 1260, consisting from quaternary gradient pump, autosampler for 100 samples,
thermostatted column compartment and DAD,was composed. Figure 2 shows complete
instrumentation of HPLC-DAD and a sample chromatogram of quantitative analysis of extracts
from robinia heartwood, focused mainly on flavonoids and other phenolic compounds. The
dominant peak in the chromatogram is flavonoid dihydrorobinetin.
Figure 2: HPLC-DAD instrumentation and determination of flavonoids in the extracts of robinia heartwood
chromatogram.
Spectrophotometry: Single-beam UV-VIS spectrophotometer Metash Instrumentswas
chosen. Figure 3 shows spectrophotometric determination of total phenolic and polyphenolic
compounds in extracts from subfossil oak. The method is based on a colour reaction of
phenolic compounds with Folin-Ciocalteu reagent in the presence of sodium carbonate.
Absorbance is measured after 30 min at 700 nm. The amount of phenolic compounds is
expressed as gallic acid equivalent (GAE). Gallic acid is used as a standard of phenolic
compounds.
Figure 3: Spectrophotometric determination of total phenolic compounds in extracts from subfossil oak –
spectrophotometer, calibration series for gallic acid, used for ultrasonic extraction of wood from subfossil oak.
CONCLUSION
The current analytical options of the laboratory, supplemented by cooperation with other
national (Academy of Sciences) or international universities and research centers (e.g. Vienna,
Hamburg, Göttingen, Ghent, Zvolen, Sopron, Ljubljana, Poznan) allow us to achieve analytical
efficiency.
50
ADJUSTMENT OF AIR POLLUTION INDOORS CONTAMINATED
WITH CIGARETTE SMOKE THROUGH CONTROLLED IONIZATION
J. Tauber* & J. Svoboda
Department of Furniture, Design and Habitat
*
INTRODUCTION
Humans may live one or two weeks without food, one or two days without water, but not
even five minutes without air. Air and its composition, mainly from the chemical point of
view, influences the overall state of well-being of everyone. The interior environment, where
we spend most of our time, is polluted by various harmful substances. Some of the significant
substances polluting this space are organic volatile substances, then cigarette smoke, dust
particles and other impurities. These substances may cause lifestyle diseases and it is only
natural to try to restrict their negative influence on the human organism. One of the ways we
can reduce the substances emitted into the air is removing them using atmospheric negative
ions.
BASIC CHARACTERISTICS OF ATMOSPHERIC IONS
Atmospheric ions are electrically charged molecules, parts of molecules or molecular
clusters, which come into existence through ionization of the gaseous components of the
atmosphere. To ionize the air an ionizing energy is needed and the sources of such energy
constantly work on the terrestrial surface. That is why the natural air is ionized at every
moment.Division of ions based on polarity: Positive – represented by nitrogen ions in the
nature, Negative – represented by oxygen ions and water-vapor ions.
ARTIFICIAL AIR-IONIZATION
Nowadays, various home air ionizers can be found on the market. These are so-called ion
generators, which produce either ions of both polarities, or they are constructed in such a way
that positive ions are captured inside the generator immediately and only negative ions are
released. Thus the generator provides only those ions which are beneficial and required in
terms of biological effect on humans. Such generators operate on various principles.
GOAL
The goal of this paper is to show a possible enhancement of the quality of the interior
environment using the controlled air-ionization. With the help of the described measurements,
the influence of negative ions on the concentration of selected substances comprised in a
cigarette smoke setting was observed. A special testing device was designed for the individual
measurements, which measured the influence of the concentration of ions on the cigarette
smoke in the interior. A number of measurements were carried out, when the space was
polluted by smoke emissions of NO, CO and NO2 from two burning tobacco cigarettes. The
measurements helped to identify how long the testing environment remained polluted, the
concentration of smoke emissions after the pollution and the changes in concentration during
ionization recorded at previously set time intervals.
51
MEASUREMENT RESULTS
The concentration of individual substances was first measured before turning the artificial
ionization on, the figures are shown as 0 min. After turning the ionization on, changes in
concentration were taken down every 15 minutes. The highest and the lowest average figures
of CO are shown in Fig. 1. The change in concentration decreased gradually with time. Trend
y= -0.8179x+340.37, with a reliability R2=0.9949, was discovered through the regression
analysis.
Figure 1: The change in average concentrations of carbon monoxide (CO) in a test environment using artificial
ionization
CONCLUSIONS
Artificial ionization enriches the interior environment by beneficial, light, negatively
charged particles and at the same time the elimination of pollutants occurs, both those which
arose from smoking tobacco cigarettes, and other polluting substances or particles. Through
laboratory measurements it was discovered that the average concentration of CO decreased by
almost a half in 180 minutes. At time t=0 minutes the concentration was around 344.8 ppm on
average, and the value decreased to 195.8 ppm at 180 minutes. Reducing the amount of CO in
the test device showed a practically continuous linear trend. Regarding the second tested
substance, NO, a complete elimination of NO was achieved by the artificial ionization after 45
minutes. The artificial ionization created NO2, which cannot be avoided when using the ionizer
based on the principle of corona discharge. The concentration of NO2 increased gradually with
the influence of ionization.
REFERENCES
[1] Spenggler J, McCartny F, Samet M (2001) Indoor Air Quality Handbook, McGraw-Hill
Professional, ISBN 9780074455494
[2] Jokl M (2002) Zdrave obytne a pracovni prostredi, 1. ed. Praha: Academia, 261 p., ISBN 80200-0928-0
[3] Lajčíková A (2007) Syndrom nemocnych budov, Kancelar, 10, 38-39
[4] Svoboda J, Muzikař Z, Čech P (2010) VOC latky a jejich vliv na iontovou rovnovahu interieru
budov, Trendy v nabytkarstvi a bydleni 2010, Brno: ES Mendel university, 2010, p. 121-128.
ISB 978-80-7375-451-8
52
HEAT TRANSFER THROUGH A WOOD-BASED WALL WITH AN AIR
LAYER
M. Švehlík1, E. Troppová1, J. Tippner1, R. Wimmer2
1
2
University of Natural Resources and Life Sciences
Konrad Lorenz Strasse 20, 3430 Tulln, Austria
INTRODUCTION
The aims of this work are to characterize heat transfer in a part of a wooden construction
with an air cavity and to investigate a possible increase in the thermal resistance by means of
low emissivity aluminium foil.
Multi-layer insulation material consisting of plywood, aluminium reflective foil and air gaps
was investigated by [1].[2] studied the impact of cavity thickness on a block of exterior wall
thermal conductivity by the means of a guarded hot box.The thermal resistivity of an enclosed
air cavity with reflective surfaces was investigated by [3] at different inclinations and
directions of a heat flow.
MATERIALAND METHODS
Diffusion-opened, dry-processed, 32 mm thick insulation fibreboards with hydrophobic
treatment were investigated. The average thermal conductivity is 0.063 W.m-1.K-1 at a mean
density of 270 kg.m-3, based on ISO 8301:1991.
Ten samples were cut to a size of 600 x 600 mm, conditioned in a Sanyo MTH 2400
chamber at 20°C and 65% relative humidity until reaching weight constancy (< 0.1%). A frame
from the same material was placed between the two fibreboards to create an air gap 5–20 mm
thick at 5 mm increments.
The effective thermal conductivity of the construction was measured across the thickness
using the heat flow meter HFM 436 Lambda by Netzsch® set to 20°C mean temperature and
10°C difference between the hot and the cold plates. Samples were wrapped in polypropylene
foil (0.01 mm thick) to avoid the air movement and moisture content changes.
At first, solely fiberboards were measured to compare thermal conductivity values with the
normative ones. Afterwards, measurements with different air gap thicknesses were held.
Finally, reflective foils with aluminium cover were placed on both inner sides of fibreboards to
enclose the air cavity. Thermal measurements were then repeated at the same cavity
dimensions. All used materials were diffusion-opened which enabled air movement within the
entire structure. Thermal conductivity was calculated based on the following equation:
x  x.(qupper  qlower )

T
2.T
where q is the heat flow [W]; λ the thermal conductivity [W.m-1.K-1]; A the area [m2]; ΔT
  N.
53
the temperature difference [K]; Δx the thickness of the sample [m]; N the calibration factor
[W.m-2].
The heat transfer through a multilayer structure consists of heat conduction in the solid
materials, convection in the air cavity and radiation between the inner cavity surfaces. The ratio
of change in transferred heat via radiation depends on the temperature difference between
surrounding plates and the air cavity thickness. The presumption is therefore that at low
temperature differences the radiation part of the total heat flow is also low.
REASULTS AND CONCLUSIONS
According to experimental data, the thermal conductivity values increase with an increasing
air gap thickness for the measurement without reflective foil. This was also proved by e.g.[1].
This happens at a rising pace as the influence of thermal convection escalates relatively to the
conduction. The coefficient of variation increases with the air gap thickness, which is probably
caused by the air movement in the cavity. This assumption is supported by the increased
measuring time.
Table 1: Experimental thermal conductivity values of the system with air gaps (values in parentheses describe
coefficient of variation)
Air gap thickness [mm]
Effective thermal conductivity
λ [W.m-1.K-1]
0
5
10
15
20
0.0536 0.0537 0.0557 0.0588 0.0617
Without reflective foils
(0.09) (0.24) (1.62) (1.92) (2.13)
0.0541 0.0531 0.0508 0.0517 0.0532
With reflective foils
(0.99) (2.10) (1.70) (1.19) (0.76)
Experimental measurements also proved that addition of a reflective foil lowers the thermal
transmittance at each air gap thickness. The higher the air gap thickness, the bigger the
difference in the thermal conductivity between the setting with and without reflective foils.
Table 2: Experimental thermal transmittance values of a composition with air gaps (values in parentheses describe
coefficient of variation)
Air gap thickness [mm]
0
5
10
15
20
0.8400 0.76054 0.7393 0.7337 0.7145
Without reflective foils
(0.09)
(0.14)
(1.11) (1.96) (2.04)
0.8002 0.7462 0.6678 0.6316 0.5797
With reflective foils
(0.84)
(2.34)
(1.56) (1.29) (1.03)
Thermal transmittance
U [W.m-2.K-1]
REFERENCES
[1] Pasztory Z, Peralta PN, Peszlen I (2011) Multi-layer Heat Insulation System for Frame
Construction Buildings. Energy and Buildings 43:713–717.
[2] South J, Blass B (2001) The future of modern genomics. Blackwell, London
[3] Aviram DP, Fried AN, Roberts JJ (2001) Thermal Properties of a Variable Cavity Wall.
Building and Environment 36:1057–1072
[4] Saber HH (2012) Investigation of Thermal Performance of Reflective Insulations for Different
Applications. Building and Environment 52:32-44
54
Session III
Wood and Fiber Property
INWOOD PROJECT: EDUCATION AND GROUP BUILDING FOR
INNOVATIONS IN WOOD MATERIALS AND PROCESSES
P. Rademacher*, R. Wimmer, P. Horáček, V. Gryc, J. Kúdela
*
INTRODUCTION
In summer 2012 the EU/CZ-funded project InWood was started. The objectives of the
project were: to educate and to build up a new group of young wood researchers, to investigate
native wood properties of a wide range of wood species, to detect existing discrepancies in
availability and demand of wood quantity as well as in native wood quality and demanded
technical requests for higher value, to improve wood properties by wood modification, and to
make new materials available for new innovative products.
Wood modification can help to improve insufficient wood properties. In contrast to
conventional wood protection with biocide treatment, wood modification works on the basis of
structure changes of wood components, influencing a lot of wood properties, like anatomical
structure, moisture behavior (humidity uptake, swelling/shrinkage), physical and elastomechanical properties as well as durability of solid wood or wood based fiber materials.
In addition, the mainly toxic-free composition of wood modification agents leads to
environmental friendly process conditions and non-complex admission requirements.
Furthermore, not only toxic-free, but also sustainable and renewable production and
application processes, using native solutions from plant growing components have been
developed by Mendel wood research group. Investigated and modified wood species were the
main important species used in practice as well as lesser known or lesser used species and their
assortments and materials of forest, plantation or agricultural origin.
METHODOLOGY [1-5]
Based on methods or examination facilities available at Mendel-University as well as exchanged with other European wood research centers, following studies have been carried out:
 Anatomical-structural tests of wood, using light- [Brno], electron-microscopic, digital
image technics (FE-SEM [Zvolen], UMSP [Hamburg], Nanotome [Göttingen], Computer-tomography [Telc]); process behaviour and modelling of data (FEM [Ghent, Br]
 Moisture related investigations of dimensional stability (emc, ASE, swelling/ shrinkage
[Br], DVS [Vienna], Bulking, DIC-camera-technique [Br]
 Physical tests (density [mass/ vol., X-ray, comp.-tomography], surface roughness [Zv])
 Elasto-mech. tests (bending-, compression-, tensile-strength [Zwick: Br], 0-Span [Gö]
 Chemical analysis (structure components, inorganic [WIESE, TAPPI, ICP: Ha,
Eberswalde],VOC[GC:BR],extracts[GC, HPLC,Spectrophotometer:Br],UMSP[Ha]
 Thermal conductivity [Netzsch-HFM436:Br], Ultra-Sonic Sound-Timer [Fakopp: Br]
RESULTS
With help of investigations listed, lots of solid (beech, forest/ plantation poplar, for./ plant.
robinia, ash, oak, Eur. chestnut, hornbeam, spruce, pine) and peeled, defibrated or
56
chippedwood based materials have been investigated concerning their natural quality, their
possible utilization, the lack of quality or need for property improvement for higher value
demands.
Following applied treatments and material developments can be named as examples of a
wide range of new established materials and innovative products (furniture, flooring, cladding): Lignamon process ([1] Beech wood ammonification + heat treatment + densification),
wood densification (+Koper), heat treated wood ([2] KATRAS Comp.[be, sp, as, po, oa]),
microwave treated wood ([3] ROWMIL [be, po, sp]), impregnation of wood ([4] be, po, pi, ro,
ho) with native-renewable agents (extractives [+Sopron], pyrolysis [+Ha], HT and HTC [Eb]
solutions, liquid-wood [+Ljubljana]), alternative layered wood-based panels (residues, cork
[6]), 3-D-imprints, agricultural process residues as particle board and glue alternatives.
Figure 1: Modified beech wood after densification, pyrolysis impregnation, material mix and NH3-treatment (l-r)
CONCLUSIONS






Establishment of a young wood research group at Mendel University.
Education with help of international exchange on new methods, processes and materials.
Properties of > 10 applied wood species or those used less have been characterized.
Most of them showed lack in natural quality, preventing higher value utilization.
Use of different modification techniques and alternative use of materials and adhesives.
Establishment of new properties of modified materials for innovative new products.
REFERENCES
[1] Pařil P, Brabec M, Maňák O, Rousek R, Rademacher P, Čermák P, Dejmal A (2014)
Comparison of selected physical and mechanical properties of densified beech wood plasticized
by ammonia and saturated steam. Eur J Wood Prod 72(5):583-591
[2] Čermák P, Horáček P, Rademacher P (2014) Measured temperature and moisture profiles
during thermal modification of beech (Fagus sylvatica L.) and spruce (Picea abies L. Karst.)
wood. Holzforschung 68(2):175-183
[3] Koiš V, Dömény J, Tippner J (2014) Microwave Device for Continuous Modification of Wood.
BioResources 9(2):3025-3037
[4] Sáblík P, Rademacher P (2014) Varied extract gain of 'Accelarate FEX-IKA Extraction' and influences of different process parameters. In: R. Nemeth, A. Teischinger, U. Schmitt (eds): Ecoefficient Resource Wood. Hardwood-Conference/ Sopron/ Vienna, 15.– 18. Sept. 2014, 43-44
[5] Brabec M, Tippner J, Sebera V, Milch J, Rademacher P (2015) Standard and non-standard
deformation behaviour of Eur. beech and Nor. spruce during compression. Holzforsch.1
[6] Král P, Klímek P, Mishra PK, Rademacher P, WimmerR (2014) Preparation and characterization of cork layered composite plywood boards. BioResources 9(2):1977-1985
57
VIBRATION RESPONSE OF NORWAY SPRUCE DURING SORPTION
A. Straže1,*, J. Tippner2, Ž. Gorišek1
1
University of Ljubljana, Biotechnical Faculty
Jamnikarjeva 101, SI-1000 Ljubljana, Slovenia
*
2
INTRODUCTION
The dynamic material testing often uses vibration response for fast and reliable nondestructive determination of mechanical properties. The homogeneous distribution of material
mass with zero- or balanced stress distribution is the usual presumption at these tests [1]. Due
to the hygroscopic nature of wood, the state is only achieved in steady state circumstances,
after long enough climate conditioning. On the other hand, the exposure of wood and wood
based materials to variable climate causes redistribution of internal moisture and consequently
induces moisture- and stress-strain gradient. Such conditions need to be researched for proper
dynamic characterization of mechanical properties of wood.
Clear wood Norway spruce specimens (n = 20), having two sizes (A: 15 × 15 × 270 mm and
B: 30 × 30 × 470 mm (w2×L; w - width, L - length)), were conditioned at 20 °C and 33%
relative humidity (RH). Specimens were exposed afterwards to 75% RH, periodically weighed
where also impact forced free-free flexural vibration was imposed, using steel ball.
Displacement was measured at a belly of vibration by a condense microphone (PCB–130D20),
where the signal was acquired by NI-9234 data acquisition module.
Diffusion coefficient (D) was determined by traditional unsteady state method, using
fractional change in average MC (Eq. 1) [2], in the first part of average dimensionless mass ( E
) – time (t) response (Eq. 1). The first resonant frequency (f1) was used from which the
dynamic modulus of elasticity (MOE) was deduced according to the Euler-Bernoulli equation
(I – moment of inertia, A – cross section) (Eq. 2). The damping coefficient (tan δ) was
calculated using least-squares regression analysis of the decay curve, using coefficient of
temporal damping (α) (Eq. 3).
E  w
D
2
3
5.1  t
4 2 L4 f12 A
MOE 
I  4.734
tan  
58

  f1
(1)
(2)
(3)
RESULTS AND DISCUSSION
The dominated internal moisture flow resistance (DA = 3.31×10-10 m/s2; DB = 3.71×10-10
m/s2) caused first order response of mass of specimens during adsorption. The time constant in
adsorption was 26.2 h and 50.1 h at A- and B-size specimens, respectively. The change of
natural frequency was 70% faster at A-size specimens (τ = 15.2 h), and almost doubled at Bsize specimens (τ = 26.3 h). The differences in time constants between mass change and
frequency change caused non-linear dependence of modulus of elasticity on average wood
moisture content. The fastest change was noticed at damping of vibrations (τA = 16.6 h; τB =
9.1 h)
Figure 3 The change of moisture content (left), natural frequency (middle) and vibration damping (right) in adsorption
of A-size (1st row) and B-size specimens (2nd row).
Figure 4: Dependence of modulus of elasticity on moisture content at A-size (left) and B-size specimens (right).
CONCLUSIONS
The sorption of spruce wood followed the First-Order-System response, where the fastest
changes were confirmed at vibrationdamping, slightly slower at natural frequency change, and
the slowest at mass of specimens. Due to the difference in response rate of tested values the
steady state conditions without MC gradient are needed for an accurate determination of
natural frequency and vibration damping.
REFERENCES
[1] Brancheriau L, Bailléres H (2002) Natural vibration analysis of clear wooden beams: A
theoretical review. Wood Sci Technology 36:347-365
[2] Stamm AJ (1960) Combined bound-water and water-vapour diffusion into sitka spruce For
Prod J 10:644-648
59
FIBRE CUBE - HOW TO MEASURE FIBRE SIZE DISTRIBUTION
M. Ohlmeyer1,*, S. Helder1, J.T. Benthien1, B. Seppke2
Thünen-Institute of Wood Research
Leuschnerstrasse 91c, D-21031 Hamburg, Germany
*
e-mail: martin.ohlmeyer
e-mail: sabrina.heldner, [email protected]
1
2
University of Hamburg, MIN Faculty, Department of Informatics, Cognitive Systems Laboratory
Vogt-Kölln-Str. 30, D-22527 Hamburg, Germany
INTRODUCTION
Particle size distribution and morphology are classified as important factors for the
industrial production process and the resulting product properties of wood-based panels.
However, fibre quality control for medium-density fibreboard (MDF) production is mainly
performed on a quite low sophisticated level because adequate measurement systems are still
not available.
Current fibre characterization approaches appear to be limited in reproducibility and/or do
not fit to process control purposes. Therefore, our aims are to (1) introduce a recently
developed particle analysis system that fulfils the requirements for MDF fibre characterization,
and (2) show how defibration conditions, fibre size distribution, and fibreboard properties
correlate with each other. Several different fibre types were produced by e.g. varying the
steaming time and temperature of a thermo-mechanical refiner process - fibre size distribution
was determined and analysed. Furthermore, the system was tested in an industrial plant in
order to follow the fibre size distribution for various panel types as well as over the life span of
the refiner disc.
EXPERIMENTAL
Despite the importance of fibre quality for MDF production, its evaluation is still just done
on a low technical level as a worldwide survey of MDF plants showed recently. The overall
majority of fibre quality control is yet performed by skilled personnel (haptical and visual),
followed by the application of various sieving methods and optical measuring systems with
obviously limited capabilities. Based on this initial situation, an alternative mass image-based
fibre analysis system was developed by the Thünen Institute of Wood Research (Hamburg,
Germany); Hamburg University (Hamburg, Germany), in particular Department of Wood
Science and The Cognitive Systems Laboratory (KOGS); and Fagus-GreCon Greten GmbH &
Co. KG (GreCon) (Alfeld, Germany). As a result of the conducted research projects, and on
basis of the algorithms presented herein, an offline fibre characterization system has proved to
work stable in a three-month industrial trail.
The technical set-up of the measuring device hardware component can be roughly
partitioned into three sections: mechanical fibre separation, image acquisition, and cleaning
(Fig. 1). The mechanical fibre separation is arranged by means of specially tuned airflows, and
finishes when the fibres land as a fine scattered film on the continuously rotating glass plate,
which can be considered as the objective plate. Passing the photo unit, the fibres are imaged
with an industrial high-resolution grey scale.
60
The image-analysis software, which was developed for this particular purpose, facilitates
two different methods in order to measure fibre-size in a sub-pixel accuracy and to separate
possibly overlapping fibres: fibre-tracing and image moment methods. This enables the
determination and calculation of various fibre characteristics, i.e. fibre length, width and
slenderness ratio as well as the relative fibre number, some fineness characteristics and shive
content.
Hardware&
With this method it was possible to show the effect of the refining process on the fibre size
characteristics, i.e. wood species, refiner disc gap, and others, which will be given in the
presentation.
Mo5va5o
SoVwar
Hardwar
Performan
Figure 1: Diagram of the experimental setup of FibreCube.
slide&9&
9"Oct"2014"
CONCLUSIONS
Ohlmeyer&et&al.&
9th"EWBPS"
 FibreCube is a suitable new method to measure fibre size distribution.
 The system is able to measure minimum 250k fibres in less than 10 minutes with a
resolution of 23.2 µm.
 The results clearly indicate the effect of refining parameters on the fibre size distribution
as well as their influence on panel properties.
 The potential for further research under laboratory and industrial conditions can be
demonstrated.
61
THE RESISTANCE OF COMPOSITE BOARDS TO DECAYING FUNGI
AND MOULD
J. Zabielska-Matejuk1,*, I. Frąckowiak2, A. Stangierska1
1
2
Wood Technology Institute, Wood Protection Department
60-654 Poznan, ul. Winiarska 1, Poland
*
Wood Technology Institute, Department of Wood-based Materials and Glues
60-654 Poznan,ul. Winiarska, Poland
INTRODUCTION
In Europe the increasing demand for wood-based panels contributed to widening of their
assortment and production capacity. Currently, the general trend is the production of intendeduse boards that are human and environmentally friendly. Wood-based panels are used in the
furniture industry for furnishings, in construction, in the packaging industry, etc. The
development of wooden construction requires new solutions in the area of protecting these
materials against biological corrosion. The problem of mould growth on lignocellulosic boards
limits the range of their indoor and outdoor applications in conditions of high humidity. In
order to increase the resistance of wood-based panels, one uses preservatives applied on the
surface or by pressure impregnation, which entails reduction of the strength properties, both
mechanical and physical, of the panels [1,2,3]. In the past, the boards were effectively
protected through introduction in the technological process of toxic biocides such as: copper
naphthenate, pentachlorophenol, acidic ammonium fluoride, etc. [4]. The Wood Technology
Institute developed technologies of protection of wood-based composite panels in the
production process using environmentally friendly fungicides.
EXPERIMENTAL
In this paper a study on the resistance of wood composite boards, glued with silicone
adhesive and obtained from chips of Scots pine Pinus silvestris L. and willow Salix viminalis
L., to basidiomycetes and mould were presented. The boards were protected in the production
processes with fungicides based on metal nanoparticles, as well as on derivatives of 1,2,4triazole, benzimidazole, and thiazole. Mycological examination was carried out in relation to
white-rot fungiTrametes versicolor and Pleurotus ostreatus and brown-rot fungus Coniophora
puteana and to a mixture of mould fungi and Chaetomium globosum. The complete resistance
of the composite boards to decay caused by brown-rot fungi was obtained by the adding a
mixture of fungicides in an amount of 0.5% wt (average mass loss of 1.1%, DSI index 3.1)to
the silicone adhesive.
62
CONCLUSIONS
 The developed ecological composite boards protected with fungicides on the basis of
azole demonstrated full resistance to basidiomycetes and mould.
 They can be used in buildings, in high humidity conditions conducive to the occurrence of
biological corrosion of lignocellulosic materials.
REFERENCES
[1] Hall H J, Gertjejansen RO, Schmidt EL, Carll C G, DeGroot RC (1982) Preservative treatment
effects on mechanical and thickness swelling properties of aspen waferboard. For Prod J 32:1926
[2] Tsunoda K, Muin M (2003) Preservative treatment of wood-based composites with 3-iodo-2propynyl butylcarbamate using supercritical carbon dioxide impregnation. JWood Sci49:430436
[3] Tascioglu C, Tsunoda K (2010) Laboratory evaluation of wood-based composites treated with
alkaline copper quta against fungal and termite attack. Int Biodeter Biodegr64:683-687
[4] Gardner D J, Tascioglu C, Walinger M E (2003) Wood composite protection. In: Wood
deterioration and preservation: advances in our changing world. B. Goodell, D.D. Nicholas, and
T.P. Schultz, eds; American Chemical Society, Washington D.C.: 399-419
63
EVALUATION OF DECAY RESISTANCE OF LIGNAMON
J. Baar
INTRODUCTION
Wood densification after its plasticization is a well-known technique providing
improvement of the wood mechanical properties, such as hardness or compression strength.
The product of this technology process, where beech wood is plasticized by ammonia gas and
then densified in perpendicular direction to wood fibers, is called Lignamon. The changes in
density, mechanical properties, colour or swelling and shrinking are well documented [1, 2, 3,
4]. On the other hand, the modification of decay resistance following from alternation of
chemical and anatomical structure due to ammonification, densification and thermal treatment
is not known.
For the experiment, samples were cut from 15 prisms with dimensions of 740×80×35
mm3which came from an old production process of Lignamon. The samples origin and process
itself is described in Pařil et al. [4]. Two specimens with dimensions of 50×25×15 mm3 were
prepared from each prism. One specimen from the couple was subjected to leaching test
according to standard EN 84 for fourteen days. Mass loss due to fungus Trametes versicolor
was measured in laboratory test according to standards EN 350-1 and EN 113. Beech wood
was used as a reference. Decay susceptibility, which is considered to be a more reliable value
when comparing specimens of different density [5], was calculated as follows:
DS  (m0  m1 ) V [g/cm3],
where m0 is the original dry weight [g], m1 is the dry weight after decay [g] and V is the
volume of the sample [cm3].
RESULTS
The average mass loss of the beech reference samples equals to 35.5 %. Lignamon decay
resistance was considerably higher (Table 1). Only four samples showed mass loss higher than
3.5 % after the durability test. The nonobservance of technological process parameters
involving inadequate chemical changes in wood is probably the main reason for different
behaviour of the samples. The weight loss after leaching ranged from 1.35 to 3.88%, but the
effect of leaching on decay resistance was not clear. An increase as well as a decrease in
durability were observed. Skyba et al. [3] examined durability against T. versicolor of thermohygro-mechanically densified beech wood and stated lower mass loss compared to control
samples. This was attributed to restriction of fungal growth by the occlusion of cell lumens. On
the other hand, decay susceptibility was comparable or slightly higher in THM beech wood,
which means that this material was still susceptible to fungi decay. In case of Lignamon, DS
was four to six times lower when compared to reference samples. The role of chemical
structure alternation during the process and a higher amount of nitrogen (1.5 %) must be
considered to find reasons for higher durability of Lignamon.
64
Table 1: Mean values of specimens mass loss (ML), decay susceptibility (DS), moisture content (MC) after fungi
exposure and absolute dry density (ρ0) (coefficient of variation in parenthesis).
ML [%]
6.37 (97.0)
3.96 (93.3)
35.5 (25.4)
Leached Lignamon
Unleached Lignamon
Beech
40
leached
35
Mass loss (%)
DS [g/cm3]
0.06 (96.5)
0.04 (92.2)
0.24 (23.6)
MC [%]
45.6 (21.7)
51.9 (23.2)
71.6 (23.0)
ρ0 (g/cm3)
1.068 (8.8)
1.071 (8.5)
0.677 (6.5)
unleached
30
25
20
15
10
5
0
B
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15
Figure 1: Mass losses of beech and leached and unleached Lignamon specimens after 16 weeks incubation with
Trametes versicolor.
CONCLUSIONS
 Lower mass losses and decay susceptibility of Lignamon when compared with native
beech wood.
 The mean value of leachability was 1.85%, but the effect on durability was not clear.
 High amount of nitrogen in Lignamon.
REFERENCES
[1] Bach L, Hastrup K (1973) Compression densification of beech wood plasticized with
anhydrous ammonia, Matériaux et Construction 6:137-139. doi. 10.1007/BF02475146
[2] Czerny R, Valasek V (1974) Lignamon – a new pattern material. Russ Cast Prod 12:506-507
[3] Holan J, Merenda L (2008) Selected mechanical properties of modified beech wood. Acta
Universitatis
et
Silviculturae
Mendelianae
Brunensis,
56:245-250.doi:
10.11118/actaun200856010245
[4] Pařil P, Brabec M, Maňák O, Rousek R, Rademacher P, Čermák P, Dejmal A (2014)
Comparison of selected physical and mechanical properties of densified beech wood plasticized
by ammonia and saturated steam. Eur J Wood Wood Prod 72:583-591. doi: 10.1007/s00107014-0814-8
[5] Nilsson T, Daniel G (1992) On the issue of % weight loss as a measure for expressing results
of laboratory decay experiments In The International Research Group on Wood Preservation.
Document No:IRG/WP/2394-92
[6] Skyba O, Niemz P, Schwarze FWMR (2009) Resistance of thermo-hygro-mechanically (THM)
densified wood to degradation by white rot fungi. Holzforschung 63:639-646. doi:
10.1515/HF.2009.087
65
INTERACTIONS BETWEEN UV LACQUERS AND WOOD
M. Štrbová1,*, D. Tesařová2, J. Kúdela1
1
Ul. T. G. Masaryka 24, 960 53 Zvolen, Slovak Republic
*
2
INTRODUCTION
The interactions between coating materials and wood significantly influence the quality of
wood surface treatment and, consequently, the quality of the end products. The modern
ecological trends prefer using coating materials with reduced volatile organic compound
(VOC) content, such as UV cured coatings. The aims of this work were to study the
interactions between beech wood and two types of UV lacquers in liquid and solid phase
through their thermodynamical characteristics and to compare the results obtained
experimentally with the actual condition at the interface lacquer-wood.
The experimental material consisted of radial and tangential beech specimens with dimensions
of 20  100  200 mm and a moisture content of about 10 %. The specimen surface was sanded.
We used two commercially produced UV cured high-solids lacquers (priming and finishing).
Surface free energy was assessed with a goniometer Krüss DSA30S – the method used for
liquid lacquers was pendant drop, the method used for wood and solid lacquers (free films) was
sessile drop. The test liquids were apolar and apolar-polar.
The disperse and polar components of surface free energy of wood and lacquers were
determined by the methods described in [1, 2], for liquid lacquers based on the contact angle values
of a sessile drop on paraffin, the parameters of which are known.
These values were used in calculation of thermodynamical characteristics describing the
interactions between coating material and wood. The stability of the system wood – solid coating
was verified by a pull off test and the location of the break was determined with the aid of electron
microscopy.
RESULTS
The surface free energy values of the two tested UV lacquers in liquid phase were equal or
higher than the values of solvent-based lacquers studied in [1]. The surface energy values of
lacquers in this work were similar to the values of surface free energy of water-based lacquers
[1]. Higher surface free energy of the priming UV lacquer followed from the higher value of its
disperse component compared to the finishing lacquer as well as compared to the lacquers
discussed in [1]. The values of polar component of surface free energy of the finishing UV
lacquer were three times higher than the corresponding values of the priming lacquer. Surface
free energy of solid surfaces, determined according to the methods reported in [3], was 79.1
66
mJ∙m–2 for wood, 57.1 mJ∙m–2 for the priming and 54.3 mJ∙m–2 for the finishing UV lacquer in
solid phase.
The surface energy values of wood and lacquers were used for calculation of
thermodynamical characteristics describing the interface between wood and coating materials:
work of lacquer adhesion to wood, work of wood cohesion, work of lacquer cohesion, and
spreading coefficient of lacquer on wood.
The results imply that the adhesion of coating materials in liquid phase to wood is
determined by interactions among nonpolar and polar forces at the interface between wood and
coating material, mostly interactions within disperse components of surface free energy of the
neighbouring phases, because of the low polarity of coating materials. The cohesion of coating
materials in liquid phase is lower than their adhesion to wood. Therefore, the spreading
coefficients of lacquers on wood are higher than 0, which means that the studied lacquers
should spread spontaneously over the wood surface.
During the curing of UV lacquers, their surface free energy increased, as well as their
adhesion to the substrate. In the priming UV lacquer, this was mainly due to interactions
between the polar components of surface free energy of the neighbouring phases; in the
finishing lacquer, interactions between the disperse components dominated. This is in
accordance with the non-polar behaviour of lacquers. Cohesion of lacquers in solid phase was
lower than their adhesion to beech wood and lower than the wood cohesion. This suggests that
lacquers are the weakest part of the system.
The pull off test confirmed that the most common type of break was cohesion failure of
lacquer in close proximity to the interface with wood. This corresponds well to the adhesion
and cohesion work values determined theoretically.
The obtained results of adhesion work as well as the results of mechanical tests show that
the adhesion of the tested UV lacquers to beech wood is good. This is in accordance with [4].
CONCLUSIONS
 Adhesion of UV lacquers in liquid phase to wood is the result of interactions among nonpolar and polar forces at the phase boundary between wood and lacquer.
 Surface free energy of solid UV lacquers after curing was higher than in their liquid phase.
Due to curing, also adhesion work of lacquers to wood increased.
 The calculated cohesion values of lacquers were lower than their adhesion to wood,
manifesting that the weakest spot of the system was in the lacquer. This was also
confirmed through the pull off test.
ACKNOWLEDGEMENT
This work was funded by: the Scientific Grand Agency of the Ministry of Education SR and
the Slovak Academy of Sciences (Grant No. 1/0893/13), the European Social Fund and the
state budget of the Czech Republic, project "The Establishment of an International Research
Team for the Development of New Wood-based Materials" reg. no. CZ.1.07/2.3.00/20.0269.
REFERENCES
[1] Liptáková E, Kúdela J, Sarvaš J (2000) Study of the system wood - coating material I. Wood –
liquid coating material. Holzforschung 54(2):189−196
[2] Liptáková E, Kúdela J (2002) Study of the system wood – coating material. Part 2. Wood –
solid coating material. Holzforschung 56(5):547−557
[3] Kúdela J (2014) Wetting of wood surface by liquids of a different polarity. Wood Research
59:11−24
[4] Bongiovanni R et al. (2002) High performance UV-cured coatings for wood protection. Prog.
Org. Coat. 45:359-363
67
ANALYSIS OF DEFORMATION DISTRIBUTION AND NEUTRAL AXIS
LOCATION IN THERMALLY MODIFIED WOOD BY MEANS OF
DIGITAL IMAGE CORRELATION
M. Brabec*, P. Čermák, J. Milch, V. Sebera, J. Tippner
*
INTRODUCTION
Thermally modified timber (TMT) has been long recognized as an efficient and eco-friendly
alternative to tropical species and wood treated by other techniques [1]. Nevertheless, the range
of feasible applications for TMT is limited by undesired side effects, such as reduction of
mechanical properties [2]. Therefore, the exploration of the mechanical performance of TMT
has always been a big issue, especially when considering it in structural applications. The
assessment of wood mechanical behaviour by means of bending tests is considered to be the
most reliable with a high predictive ability [3]. Based on [3, 4 and 5] it is evident that the
knowledge of the neutral axis (NA) location in the bended sample allows us to assess the wood
stiffness in tension compared to compression and reveal hidden wood defects, such as local
fibres deflection, knots, etc., that strongly influence the stiffness of the wood parallel to grain.
As was reported [6, 7 and 8], NA can be successfully located by means of the full-field optical
techniques.
It is hypothesized that the thermal modification affects the tensile and compressive wood
stiffness parallel to grain on a different level, so the location of NA changes. Therefore, this
paper aims to obtain the full-field axial strain data by the optical technique applying the
principles of the digital image correlation (DIC) for the NA localization in thermally modified
wood bended by the three-point loading method.
MATERIAL, BENDING LOADING AND STRAIN DATA MINING
The samples were cut from untreated and differently thermally modified (180°C and 200°C)
wood of the European beech (Fagus sylvatica L.) as clear special orthotropic blocks with a
square cross section - radial (R) × tangential (T) = 14 × 14 mm2 and length (L) equal to
15 × (R, L) = 210 mm meeting the requirements of the BS 373 (British Standard Institution
1957). Before the sampling, all source material was conditioned in a climate chamber at 20°C
and 65% relative humidity until the equilibrium moisture content (EMC) was reached. In order
to improve the image matching during DIC computation, a basic matt white paint followed by
a fine pigmented black paint was sprayed on one samples' side.
The three-point loading of the samples in the tangential direction was carried out using the
universal testing machine Zwick Z050/TH 3A equipped with a 50 kN load cell. The
deformation induced in the samples was determined by the full-field optical system consisting
of two CCD cameras at the stereovision configuration (3D). The system was calibrated to an
area of interest (AOI), which was 210 × 14 mm2, with help of calibration images at various
geometric orientations. The images were captured every 0.25 s (4 Hz) together with the applied
force. The strain fields at the AOI from the partial derivatives of the displacement using
Lagrange notation were calculated in Vic-3D (Correlated Solutions Inc.).
68
RESULTS, DISCUSSION AND CONCLUSIONS
Figure 1 shows that the variety of the zero axial strain position, i.e. NA location within the
sample height, increased as the distance from the loading point at the midspan increased. This
finding is attributable to the decreasing axial strain towards the sample ends that was apparent
as the decreasing density of the axial strain contours. As a consequence, the proportion of the
noise related to the strain values increased and the NA location became increasingly distorted,
if the constant noise throughout the AOI is taken into account. However, the NA was located
approximately in the middle of the sample cross-section height for all types of treatments.
Based on the existing results, the following can be concluded; the thermal modification did not
result in a change of the NA location.
Figure 1: Axial strain plots before the failure of European beech a) untreated; b) thermally modified at 180°C; and c)
thermally modified at 200°C.
REFERENCES
[1] Hill CA (2006) Wood modification: Chemical, thermal and other processes. Chichester, UK,
John Wiley & Sons
[2] Widmann R, Fernandez-Cabo JL, Steiger R (2012) Mechanical properties of thermally
modified beech timber for structural purposes. Eur J Wood Prod 70:775-784. doi:
10.1007/s00107-012-0615-x
[3] Kollmann FFP, Côté WA (1984) Principles of wood science and technology. Berlin, SpringerVerlag
[4] Gere JM, Timoshenko SP (1997) Mechanics of materials. Boston, PWS Pub Co
[5] Betts SC, Miller TH, Gupta R (2010) Location of the neutral axis in wood beams: A
preliminary study. Wood Mater Sci Eng 5:3-4. doi: 10.1080/17480272.2010.500060
[6] Davis PM, Gupta R, Sinha A (2012) Revisiting the neutral axis in wood beams. Holzforschung
66:497-503. doi: 10.1515/hf.2011.180
[7] Sinha A, Voigt LR, Miller TH, Gupta R (2012) Neutral axis of full-size lumber with multiple
knots. ACEM 1:1-15. doi: 10.1520/ACEM20120007
[8] Lukacevic M, Füssl J, Griessner M, Eberhardsteiner J (2014) Performance assessment of a
numerical simulation tool for wooden boards with knots by means of full-field deformation
measurements. Strain 50:301-317. doi: 10.1111/str.12093
69
Session III
Wood and Fiber Property
Poster Session
ENERGY PARAMETERS DURING MACHINING OF CHEMICALLY
MODIFIED BEECH
L. Hlásková* & Z. Kopecký
Mendel University in Brno, Faculty of Forestry and Wood Technology, Department of Wood Processing
*
INTRODUCTION
Wood, whether in native or modified form, has to be machined to the final shape to fulfill its
intended purpose. In wood processing industry, the circular-saw blade cutting is the most frequent
way to machine materials on the basis of wood. It is assumed that new wood-based materials will be
machined on existing woodworking machines and therefore it is necessary to know its behavior
during cutting.
Due to the energy consumption during machining, it is important to know cutting resistance,
which is a very significant property of the material machined. Nowadays, different modifications of
two basic methods are used for theoretical purposes and in practice – the technological and physical
method, and the analytical method [1].This paper presents a new calculating model which might be
applied for estimation of energetic effects and which uses the application of fracture mechanics[2].
The cutting process was performed with a circular saw blade, which is produced by Flury Systems
AG. This standard circular-saw blade of 350 mm diameter with straight teeth is designed for
longitudinal cutting of wood. The cutting was performed under the optimum operation speed n =
3800 min-1. Feed velocity varied within the range of vf = 2 – 22 m∙min-1with measuring step 2 m∙min1
. This corresponded with the changing feed per tooth fz and mean chip thickness hm. The experiment
was performed on a testing device used for research into circular-saw blade cutting. This device
simulates the conditions of circular-saw blade cutting in the real operation. The parameters of the
cutting process were recorded by sensors installed in the measuring stand. The signals were
transferred in the data switchboard Spider 8 and in the software Conmes Spider and subsequently
processed into tables and graphs.
In order to verify the validity and function of the new calculation model, the samples of native
beech and samples of ammonia refined wood material Lignamon (ρ1 = 1066 kg∙m3, ρ2 = 1107 kg∙m3,
ρ3 = 1185 kg∙m3) were used in the experiment. The samples were dried (relative moisture content
9%) and unified in the same thickness e = 21 mm on a thicknesser.
Data which were obtained through the experiment are very important for the determination of the
main model parameters shear yield stress Ƭγand fracture toughness R[2]. Knowing these parameters,
it is possible to make prognosis for the cutting power and cutting resistance.
Fig. 1 shows the relation of cutting force and size of mean chip thickness. Almost linear increase
in the cutting force occurred along with the growing chip thickness, which confirms the theoretical
assumptions. Samples of native beech compared to Lignamon show slightly increased values of
cutting resistance (force) at lower feed speed, however, at greater feed speeds, cutting resistance does
not increase as steeply as for native beech, see Figure 1. Regression line slope of Lignamon exhibits
accordance to the conventional methods. This is valid particularly for samples having density of 1066
71
and 1107 kg.m-3. For sample with the highest density (1185 kg.m-3), regression line slope is not as
steep as in the previous samples. The difference of regression line slope depends on whether during
cutting the sample was oriented so that the direction of compression was the same as the cutting
direction or not.
60
y = 50058x + 3,675
y = 38304x + 10,99
50
y = 39281x + 10,10
Fc [N]
40
y = 29947x + 13,97
30
20
10
0
0
0,00002
0,00004
0,00006
0,00008
0,0001
0,00012
0,00014
h m [m]
lignamon 1185
lignamon 1066
lignamon 1107
native beech
Figure 1: Cutting force as a function of mean chip thickness
The determination of the main parameters of the model is based on the regression analysis. The
R
fracture toughness ||  (for 2 = 29.3º, Fig. 1) was determined from the line Y-intercept and shear

yield stress  ||  from its slope [2,3 and 4]. The application of experimental data in the designed
model brings significant data for the longitudinally transversal cutting model to the circular saw blade
cutting process, see (Table 1):
Table 1: Results obtained by the application of fracture toughness
Beech
Lignamon 1
Lignamon 2
Lignamon 3
 (kgm-3)
µ (-)
 (°)
Φc (°)
γ (-)
Qshear (-)
  ||  (MPa)
691
1066
1107
1185
0,014
0,06
0,09
0,09
0,83
3,54
5,66
4,97
54,58
56,77
57,83
52,512
1,53
1,54
1,55
1,53
0,98
1,07
1,11
0,92
44,83
89,05
78,32
68,68
R|| 
(Jm-2)
1020,83
3052,77
2805,55
2902,77
CONCLUSIONS
On the basis of experimental measurement results we were able to determine the fracture
toughness and shear yield stress for longitudinal transversal model of cutting beech and
modified material Lignamon by a circular-saw blade. Knowing these two parameters, it is
possible to make prognosis for the necessary cutting power and cutting resistance. This model,
which is based on fracture mechanics,is useful for technologists who work in the field of wood
processing and also designers who design new saw blades.
REFERENCES
[1] Lisičan J et al. (1996) Theory and wood technology. Zvolen: Matcentrum. 626 p
[2] Atkins A G (2005) Toughness and cutting: a new way of simultaneously determining ductile
fracture toughness and strength. Eng Fract Mech 72:849-860
[3] Orlowski K, Palubicki B (2009) Recent progress in research on the cutting processes of wood.
A review COST Action E35 2004–2008: Wood machining – micromechanics and fracture.
Holzforschung, Vol. 63, iss. 2: 181–185. ISSN 0018-3830
[4] Orlowski K (2010) The fundamentals of narrow-kerf sawing: mechanics and quality of cutting,
Technical University in Zvolen, pp. 1-123, ISBN 978-80-228-2140-7
72
NATURAL DURABILITY OF SUBFOSSIL OAK
O. Nevrlý* & J. Baar
*
INTRODUCTION
The aim of this study is to investigate differences in the natural durability of recent oak and
subfossil oak. Based on a microscopic analysis, all samples of subfossil oak were identified as
the English Oak (Quercus robur L.). For this reason, the results were further compared with
the recent oak of the same species. Three subfossil oak trunks of different ages were found in
the bank of the Bečva River, near Osek nad Bečvou. All trunks were dated by radiocarbon
dating. The individual trunks come from these periods: A - 1131-804 BC; B - 208 BC - 137
AD; C - after year 1018).
Wood has a number of excellent properties and it is one of the most sustainable and
environment friendly materials. However, it also has weaknesses. One of the most obvious
properties, and also the one we decided to analyze, is its susceptibility to degradation by fungi.
The wood buried under the water surface and fully saturated with water often survived many
hundreds even thousands of years. It is exciting to know if this oakwood stays naturally
durable or its durability changes.
average mass loss (%)
The natural durability tests were carried out using European standards EN 350-1 and EN
113. Three species of wood-decay fungi were used to test natural durability, two brown-rot
fungi: Poria placenta (Fr.) Cooke and Laetiporus sulphureus (Bull.) Murrill, and one white rot
fungus Trametes versicolor (L.) Lloyd. Fungi were inoculated in malt agar medium in Kolle
flasks under sterile conditions. After complete covering of medium surface the sterilized
samples were put into flasks. As reference samples the wood of beech (T. versicolor and L.
sulphureus) and pine sapwood (P. placenta) were used. Ten samples from each set were
exposed to fungi degradation for 16 weeks, at a temperature of 22 ºC and 65% air humidity.
Finally, they were dried at 103 ºC, weighed and the differences in weight loss were recorded.
TV
40
PP
LS
30
20
10
0
English
oak
A
B
C
Beech/Pine
Figure 1: Average mass loss
73
CONCLUSIONS
Because of the changes in the chemical structure of oak wood during thousands of years, its
natural durabilitychanged. Recent oak has average mass loss two to three times lower than
subfossil oak in general. As the next step, we decided to do tannin content determination,
because tannins are responsible for the durability of native hardwood species.
74
TECHNICAL REPORT OF PAULOWNIA FORTUNEI PLANTED IN
IRAN
T. Tabarsa
Gorgan University of Agricultural Sciences and Natural Resources (GUSNER), Faculty of Wood and Paper
Engineering, Gorgan
Golestan, Iran
INTRODUCTION
Paulownia fortunei has been imported from China to Iran and it was grown in the North of
Iran educational forest of GUSNER in 1995. Many studies have been conducted on it.Data
presented below have been obtained by large research which was conducted during last 19
years. All results support plantation of Paulownia in Iran.
SUMMARY OF CONDUCTED STUDIES
Growth rate of Paulownia at the age of 14 was investigated. Paulownia fortunei height at
this age in the north of Iran (Gorgan) reached up to 21.66 m and its diameter was up to 0.41 m.
The greatest growth rate, 80 mm, was obtained at the age of three. Wood production yield in
three different plantation patterns are shown in Table 1.
Table 1: Volumetric growth at different age [m3]
Age (year)
10
11
7
8
9
0.42
0.68
0.61
0.52
0.96
0.75
0.63
1.01
0.89
0.75
1.13
1.03
0.87
1.21
1.16
12
13
14
0.98
1.28
1.31
1.09
1.32
1.46
1.20
1.34
1.59
Plantation
Pattern
5x6 m
6x8 m
7x7 m
Wood production per 10000 m2 from 277 trees was 345 m3 (Saeidi and Azadfar
2010).Physical and mechanical properties of Paulownia fortunei grown in Gorgan/Iran is
illustrated in Table 2. Strength to density ratio of Paulownia fortunei grown in Iran is 159.32
while that of Balsa is 122.25 Mpa. (Khazaeian et al. 2009).
Table 2: Physical and mechanical properties of Paulownia fortunei grown in Iran
Density [gr/m3]
MOR [Mpa]
0.26
MOE [Mpa]
41.2
Compression [Mpa]
3896.30
21.93
Table 3: Fibre dimension of Paulownia fortunei grown in Iran (Afra and Hoseini 1995)
Dimension [µm]
1
Fibre length
Fibre diameter
Cell wall thick.
800
31.000
4.140
2
895
30.850
4.383
3
920
31.381
5.810
Annual ring
4
5
948
31.273
4.628
987
32.126
5.651
6
1003
34.523
6.015
7
1097
31.490
5.893
8
1113
33.183
5.983
Table 4: Chemical component of Paulownia fortuneigrown in Iran [%] (Afra and Hoseini 1995)
Lignin
Cellulose
hemicellulose
Extractives
29.77
46.20
24.66
6.94
75
Table 5: Thickness swelling (TS) of treated and control (untreated ) Paulownia fortunei
specimen
Properties
Density
[gr/m3 ]
0.22
0.57
Control
Treated
Longitudinal TS
[%]
0.28
0.18
Radial TS
[%]
2.79
1.75
Tangential TS
[%]
5.38
3.57
Volumetrical
[5]
8.59
5.56
Paulownia fortunei is a light wood which would improve the properties of products in
particleboard industry, see Table 6 (Tabarsa et al. 20) and Table 7 (Norbakhsh et al. 2009).
Table 6: Properties of PB made of Eucalyptus and Eucalyptus plus Paulownia
PB made of:
MOR [Mpa]
Properties
IB [Ma]
TS [%]
5.96
12.21
0.04
0.18
53
16.42
Eucalyptus
Eucalyptus+Paulownia
Table 7: Properties of PB made of mixture of Paulownia and industrial particles
Percentage of
Paulownia in
Mixture
MOR [Mpa]
100
75
50
25
25.25
21.90
18.62
15.63
Properties
MOE [Mpa]
IB [Mpa]
2392
2065
1789
1524
0.91
1.09
1.28
1.16
TS [%]
8.59
8.60
10.99
14.97
During densification, Paulownia reacts like a spring because its cell walls are thin and when
the degree of compression is low most of the deformation returns to the original level. Blocks
of Paulownia fortunei grown in Iran/Gorgan were compressed at different temperatures (130 oC,
140oC and 160oC) and at 16%, 33% and 50% compression. The results are shown in Table 8.
Table 8: Densification characteristics of Paulownia fortunei grown in Iran/Gorgan
Compression
SP
Comp. set
MOE
MOR
Shock
[%]
[%]
[%]
[MPa]
[MPa]
[N/m]
16
33
50
12
19
35
8
22
33
4500
5100
6000
55
72
81
15
15
20
REFERENCES
[1] Saeidi Z, Azadfar D (2010) Effect plantation pattern on growth properties of paulownia.
Journalof Iran forest, Association of Iranian Forest 2(2)
[2] Khazaeian A, Yagmaei F, Tabarsa T(2009) Study of bending and compression strength of
paulownia planted in Iran. Journal of wood and forest science and technology16(3): 35-88
[3] Afra A, Hosseini SZ (1995) Investigation on paulownia fiber dimension and chemicals grown
in Gorgan. J. of Iran natural resources vol. 58(3)
[4] TabarsaT, Dosthoseini K, Farsi M (2010) Investigation on improving effect of paulownia in
manufacturing particleboard from Eucalyptus. Journal of Forest and wood products63(1):23-30
76
ELASTO-PLASTIC MATERIAL CONSTANTS OF MDF
H. Klímová*, J. Tippner, V. Sebera
*
INTRODUCTION
Elasto-plastic material constants describing non-linear mechanical behavior are important
e.g. for numerical simulations. Medium Density Fibreboard (MDF) is wood-based composite
exhibiting anisotropic elasto-plastic behavior. Such materials can be simplified by Hill theory
and implemented in numerical simulations as showed in [1-2]. The development of a FE
model, which incorporates nonlinear material to predict the load-deflection behaviour using
anisotropic plasticity of wood was presented in [3]. Summary of the factors influencing the
differences between the theoretical results and idealized tests on wood specimens with different
types of openings for joining components was made in [4]. [5] compiled a list of existing
measurement methods for obtaining properties of composite materials, which are described and
analyzed with respect to the further development and research in this field.
The global goals of this work were to measure material constants of MDF and to create
orthotropicelasto-plastic material model using standard and non-contact experimental methods
for later use in FE verification bending analyses.
First, specimens of MDF were scanned by the X-ray densitometer to obtain vertical density
profiles (VDP) to determine the density distribution in particular MDF layers. Furthermore,
these samples were tested by three-point bending and compressive tests in all three directions.
Data from experimental tests were processed using 3D form of Digital Image Correlation (3DDIC) to obtain elastic moduli (E1), Poisson's ratios (ν) and shear moduli (G) with respect
to strain rate and proportional limit. Plastic behavior is described by bilinear material model,
where yield stress and tangent moduli (E2) are needed. These constants were measured and
evaluated for each direction – longitudinal, radial, tangential, and their combinations. Finally,
material constants were used as the input to the finite element (FE) model of MDF at threepoint bending test suitable for verification of combined loading.
An example of measured (average density for individual layers and E1) and calculated
(ν and G for all directions) material constants for 18 mm and 25 mm MDF from experimental
compressive tests are showed in Table 1. These results are presented for face and core layer
separately without dividing the tested samples computed with use of DIC method.
Results from the experimental three-point bending test in comparison with three-point
bending values derived from global deflection and reaction force calculated by numerical
simulation show very small differences between MOE values – from 0.77 to 1.46%.
These differences are caused by different stiffnesses of experiment and FE model.
Nevertheless, this FE model with linear-elastic material model can be indicated as a successful
numerical model.
77
Table 1: Obtained material constants of 18 mm and 25 mm MDF.
Ex
Ey
Ez
xy
xz
yz
Gxy
Gxz
Gyź
[kg·m ]
[MPa]
[MPa]
[MPa]
[-]
[-]
[-]
[MPa]
[MPa]
[MPa]
18
mm_Face
775
3271,3
915,4
2044,6
0,184
0,328
0,149
1381
1231
398
18
mm_Core
700
3251,2
223,9
2032,0
0,191
0,132
0,072
1364
1436
104
25
mm_Face
775
2547,74 1080,9
1698,5
0,174
0,354
0,102
1085
940
490
25
mm_Core
700
2619,1
1746,0
0,174
0,365
0,114
1115
959
111
Density
-3
248,8
CONCLUSIONS
In this work, material constants for 3D FE structural analysis of MDF as one of wood-based
composites were presented and successfully implemented in the commercial ANSYS software.
The focus of this work was to obtain elasto-plastic material constants for simulation of bilinear mechanical behavior. In conclusion, final results are:
 the linear-elastic material constants were evaluated in dependence on the VDP,
 used properties were implemented into finite element model that exhibited 2% error of
MOE in comparison with experimental three-point bending test,
 FE analysis with combination of data gained by experiment using DIC is a suitable
process for the evaluation of mechanical properties of wood-based composites.
Moreover, the created parametric 3D FE model of MDF and results from standardized
experimental testing describe following relationships:
 with increasing thickness the mean values of Young's moduli decrease,
 parameters for face and core layer vary in dependence on density of individual
layers,differences between Young's moduli E1 and tangent moduli E2 are from 15 to 20%
for all thicknesses in each direction of loading.
Research is still in progress and further improvements and developments, such as shear
yield stress and tangent moduli as material constants for plasticity of MDF dependent on the
VPD, will be addressed in future research work.
ACKNOWLEDGEMENT
Supported by Internal Grant Agency (IGA) of Faculty of Forestry and Wood Technology, Mendel
University in Brno, (IGA I 5/2014).
REFERENCES
[1] Kharouf N, Mcclure G, Smith I (2003) Elasto-plastic modeling of wood bolted connections.
Comput Struct 81:747-754
[2] Xu BH, Bouchair A, Taazount M, Racher P (2013) Numerical simulation of embedding
strenght of glued laminated timber for dowel-type fasteners. The Japan Wood Research Society
59:17-23
[3] Raftery GM, Harte AM (2013) Nonlinear numerical modelling of FRP reinforced glued
laminatedtimber. Composites: Part B 52:40–50
[4] Zhou T, Guan Z(2006) Review of existing and newly developed approaches to obtain timber
embedding strength. Prog Struct Engng Mater 8:49–67
[5] Grédiac M (2004) The use of full-field measurement methods in composite material
characterization: interest and limitations. Composites: Part A, 35:751-76
78
Session IV
Wood Panels Composites and Processing
LONG TERM, IN-SERVICE EVALUATION OF STRIP PARQUET
FLOORING PANELS
R. Németh1 & M. Bak2
1
University of West Hungary
Bajcsy-Zsilinszky u. 4., 9400 Sopron, Hungary
2
Bajcsy-Zsilinszky u. 4., 9400 Sopron, Hungary
INTRODUCTION
Due to its extraordinary hardness, decorative appearance and possible small dimensions,
black locust wood is assumed to be an excellent material for strip parquet flooring. The
favourable colour changes achieved by controlled steam treatment further increased the
utilization potential of this material. Flooring was installed on a student dormitory stair landing
in heavy use. Due to the very high exposure of the flooring, 5 years was considered a long
enough period to compare the different face layer materials during an in-service test (Figure
1.). Oil was used as a coating to avoid the remarkable protecting effect of hard film-forming
varnishes (acrylic, etc.) against abrasion.
The main question initiating this research was whether oak (O) top layers could be replaced
by different black locust top layers (natural - N, light steamed - L, dark steamed - D). Technical
parameters, such as abrasion resistance and surface hardness, and their change due to steaming
and the in-service test, were analysed in depth. Another important question of the investigation
was whether the black locust top layers could withstand moisture-induced stresses
(delamination, deformations) at least to the same extent as oak. On the other hand, as it was an
in-service test, it was considered useful from a practical point of view to include observations
concerning visible colour changes during the service as additional information in the article.
Figure 1: The original (left) and after exposure (5 year) conditions (right) of the flooring.
CONCLUSIONS
 Under the prevailing conditions – a stair landing in a student dormitory under very heavy
traffic – the appearance of the flooring elements changed rapidly, changes clearly visible
to the naked eye after a short period (Figure 1.). However, the landing did not suffer
significant changes in structure or performance.
80
 Based on this experiment, the effect of steaming on the abrasion resistance of the flooring
top layers was found to be significant. Oiling significantly increased the abrasion
resistance of the steamed specimens, but the obtained differences in abrasion resistance
are more likely due to differences in the density and annual ring orientation (radial,
tangential) than to the surface treatment. In general, the measured differences between the
samples, although sometimes statistically significant, were small from a practical point of
view (Figure 2.). This is especially true when comparing the abrasion properties of the
black locust with those of the oak, as with one method the oak attained superior ratings,
while with the other, the black locust performed better.
 Regarding dimensional changes and deformation, the tests yielded similar results for the
oak and the natural black locust, whereas the light steamed black locust performed even
better. The dark steamed black locust proved to be inferior to all the other materials
(Figure 3.).
 To summarize the results obtained by this study on flooring element performance, both the
in-service and the laboratory tests indicated that the wood density, grain orientation and
element structure (three-ply) appear to effect the performance of the floor to a much
higher degree than the different structure and treatments of the materials used. The black
locust wood definitely proved to be the most suitable for in-door flooring applications.
Figure 2: Abrasion values measured after Taber test and indoor service (5 years).
Figure 3: Mean curvature values lengthwise and across the width at 65%, 35%, 84% RH (positive values: convex
curvature; negative values: concave curvature).
(D – dark steamed Robinia; L – light steamedRobinia; N – naturalRobinia; O – oak)
81
SELF-BONDED BIRCH PLYWOOD (BETULA PENDULA, L.): STUDIES
ON INTERNAL GAS PRESSURE DURING HOT PRESSING AND ON
POST-MANUFACTURE THERMAL MODIFICATION
J. Ruponen1,*, L. Rautkari1, M. Ohlmeyer2, M. Hughes1
1
Aalto University School of Chemical Technology
Vuorimiehentie 1, P.O.Box 16300 FI-00076 Aalto, Finland
*
Leuschnerstrasse 91c, D-21031 Hamburg, Germany
2
INTRODUCTION
During the past ten years, several researchers studied self-bonding possibilities for plywood
[1, 2, 3] to find substituting methods for conventional plywood manufacturing processes.
Several wood species, e.g. beech (Fagus sylvatica, L.) [1], sugi (Cryptomeria japonica, L.) [2]
and birch (Betula pendula, L.) [3] have shown self-bonding potential. This paper discusses the
development of internal gas pressure in the manufacture of parallel laminated self-bonded
plywood from 1.5 mm thick rotary-cut birch veneers. Additionally, the influence of postmanufacture thermal modification on the moisture stability of the bonds is presented.
EXPERIMENTAL
Ordinary plywood production utilises dried veneers of 4–5% MC on average. Compared to
this, the veneers for self-bonding process are conditioned at a relative humidity of 65% and at a
temperature of 20 °C to ensure a sufficient moisture level required for bonding. After
conditioning, the birch veneers have approximately 10–11% MC [3]. The presence of water on
such a high level is essential to enable wood-to-wood bonding. As higher moisture content
increases the risk of delamination at the hot-press opening, it was studied how the internal gas
pressure develops during the hot-pressing process.
The MC of adhesivesused commonly for plywood production is around 50%. The adhesivewood ratio varies but could be, for instance, 5%. Finally, the proportional amount of water in
lay-up is in the same range, 11–13%, as in the self-bonding process. The water is, however,
differently distributed and fully in the cell wall in the self-bonding process. In this study, the
maximum internal gas pressure was 253 kPa and the hot press temperature 150 °C [4]. Such a
gas pressure is clearly greater than those measured at particle board and MDF processes: 70
kPa and 100 kPa, respectively [5]. The high level of gas pressure stayed above 200 kPa until
hot press opening [4]. Thus, the opening may break fresh bonds that most probably have not
stabilised to full strength but are still somewhat flexible at the hot press opening.
Previous studies [1, 2] reported poor moisture stability, for instance rapid delamination, of
self-bonded plywood when immersed in water. Therefore, it was tested whether postmanufacture thermal modification could lessen or eliminate this feature. Similar treatment
clearly enhanced the bond stability of linear friction welded birch when immersed in water
[6, 7]. The self-bonded plywood boards were thermally modified for 4 hours at 200 °C under
82
atmospheric pressure using superheated steam [3]. The weight loss due to thermal modification
was 6.9% on average. The soaking test lasted for 150 hours and during the test the untreated
reference specimens delaminated within first hours in most of the bonds. The visually
evaluated bond integrity reached soon a level of approximately 5% on average, yet slowly
decreasing until the end of the test. Similar to this, also thermally modified specimens showed
delamination behaviour, especially at the outmost bonds beneath the surface veneers. However,
the bond integrity of the inner bonds did not decrease below 75% and thereby the bond
stability was clearly greater to that of non-modified reference specimens [3].
CONCLUSIONS
 The internal gas pressure of the lay-up is relatively high during and until the end of hot
pressing of self-bonded plywood. Ordinary plywood production has similar overall water
content within the lay-up and therefore the internal gas pressure may be on the same level.
The high gas pressure may weaken or break the fresh bonds at the press opening.
 Post-manufacture thermal modification enhances the moisture stability of self-bonded
plywood. However, delamination occurs also after modification when immersed in water.
Process parameter optimisation could possibly eliminate the tendency.
REFERENCES
[1] Cristescu C (2008) Bonding veneers using only heat and pressure: bending and shear strength.
Licentiate’s thesis, Luleå University of Technology
[2] Ando M, Sato M (2009) Manufacture of plywood bonded withkenaf core powder. J Wood Sci
55(4):283–288
[3] Ruponen J, Rautkari L, Belt T, Hughes M (2014) Factors influencing the properties of parallel
laminated binderless bonded plywood manufactured from rotary-cut birch (Betula pendula L.).
Int Wood Prod J 5(1):11-17. doi 10.1179/2042645313Y.0000000054
[4] Ruponen J, Ohlmeyer M, Rautkari L, Hughes M (2014) Internal Vapour Pressure of Plywood
During Hot Pressing Process. Proceedings of the Seventh European Conference on Wood
Modification ECWM7. Lissabon, Portugal
[5] Meyer N, Thoemen H (2007) Gas pressure measurements during continuous hot pressing of
particleboard, Holz Roh Werkst 65(1):49-55. doi 10.1007/s00107-006-0140-x
[6] Ruponen J, Rhême M, Ferrari S, Rautkari L, Hughes M (2013) Studies on post-welding heattreated vibrational welded wood. Proceedings of the COST Action FP0904 workshop
“Evaluation, processing and prediction of THM treated wood behaviour by experimental and
numerical methods”. Iasi, Romania
[7] Ruponen J, Rautkari L, Hughes M (2012) Influence of vacuum atmosphere thermal
modification on the bond stability of vibrational welded wood in moist conditions. Proceedings
of the COST Action FP0802 workshop “Micro-characterisation of wood materials and
properties” Edinburgh, Scotland, UK
83
IMPROVING QUALITY AND YIELD OF ROTARY PEELED BEECH
VENEERS FOR PLYWOOD PRODUCTION
H. Buddenberg*, C. Kammerloher, K. Richter
Technische Universität München, Holzforschung München
Winzererstr. 45, 80797 München, Germany
*
INTRODUCTION
Germany has had a long tradition in beech plywood production. During the last 30 years
though a decline in this industry took place due to the increasing labor costs and rising prices
of beech roundwood in Germany. Beech plywood has strength properties (i.e. bending
strength, modulus of elasticity)superior to softwood plywood and can well be defined as
engineered wood product suitable for various constructive applications. Two main reasons are
generally associated with the current marginal status of beech plywood as a commodity
product for constructive purpose. One reason is related to the weak durability of beech wood
which impedes its utilization for exterior applications. The other reason lies, at least for highly
industrialized countries, in the poor cost effectiveness of the production process. This is due to
the low degree of industrial automation and therefore the need for a relatively high share of
human labour as well as a relatively low wood yield at the end of the production process. The
latter reasongoes back to the properties of beech as wood species determining thus the
biological conditions during the production process. Due to its low durability against decay the
knots in beech wood tend to turn black and become soft spots periodicallyvisible along the
peeled veneer layer during production process. For surface veneers and for constructive
applications these spots need to be clipped out from the veneer layer, thereby the wood yieldis
reduced. Due to its relatively high density, beech wood has a high sorption capacity which
leads to high shrinking and swelling especially in the tangential direction. Therefore, rotary
peeled veneers intensely deform after the drying process and thus tend to become waved and
build cracks along the grain direction. Both appearances are undesirable for further processing.
TECHNOLOGICAL APPROACHES
During the veneer production process the highest proportion of veneer loss is caused
through the cutting phase (clipping) in which defects, i.e. knots and cracks, are selected from
the veneer layer. Experimental studies conducted in a beech plywood plant have determined
that this proportion is about 20% from the total veneer area produced, excluding the tangential
veneer loss caused by drying [1].
In our current research project we define a technique which allows for gaining higher wood
yields during rotary beech veneer production by reducing the amount of waste from veneer
clippings. Since the clipping applies along the complete length of the continuous veneer layer,
the selected veneer stripes (clippings) do not only cover regions of defects but also good
regions of veneer.
84
A
B
C
Figure 1: Veneer loss through clipping: A: Cross-section of log and peeled continuous veneer layer; B: Areas of
defects within clippings; C: Total areas of clipped veneer stripes
Statistical investigations as well as empirical studies into the actual regions of wood defects
within a continuous layer of beech veneer estimated that the proportion of a medium wood
quality (German B-grade) is at maximum only 2-2.5% [3]. On the basis of a visual analysis of
scanned veneer samples (applying image analysis software) the current research project
assesses how good areas of veneer clippings could be selected from the clippings and be
further processed instead of being treated as waste. A further research focus is the testing of
press drying of wet beech veneers on a laboratory press in comparison to oven drying of
veneers. The press dried and oven dried veneers are compared based on their tangential
shrinkage in different climate conditions and based on their planeness, dimensional flexibility
and the amount of (press) drying cracks. First results show a significant reduction in tangential
shrinkage and a higher planeness and dimensional flexibilityof press dried veneers in
comparison to oven dried veneers. Further investigations assessed and compared strength
properties of laboratory plywood panels based on press dried and oven dried veneers and
indicated that plywood panels based on press dried veneers provided the same mechanical
properties as plywood panels based on conventional dried veneers.
CONCLUSIONS
The research project demonstrated that it is possible to increase the quality, i.e. the
planeness, elasticity and yield of rotary cut beech veneers by applying press drying as an
alternative technology and to increase the veneer yield directly by using good veneer areas
from offcuts and thus reducing waste.
REFERENCES
[1] Buddenberg, Ph. A (2014) Personal record based on practical tests in 1992
[2] Keylwerth, R (1964) Über das Heißpressen von Holz. Holz Roh Werkst 22(11):11-17
[3] Marutzky R, Aderhold, J, Plinke, B (2008) Final Report of Research project: Hochwertige
Verwendung von Starkholz durch Schälfurnierprodukte aus stark dimensionierten Nadel- und
Laubhölzern-Teilprojekt 1:Evaluierung und Weiterentwicklung der Technologie zur
Herstellung von Furniersperrholz- FKZ:0330552A- financed by German Federal Ministry of
Research
[4] Paajanen, O, Holmberg, H, Lathi, P (2012): Experiences with new veneer drying method. Int
Wood Prod J 3(1):26-30
85
DIGITAL IMAGE CORRELATION IN FURNITURE TESTING
M. Šimek1,* & V. Sebera2
1
2
Zemědělská 3, 61300Brno, Czech Republic
*
INTRODUCTION
The trial and error method was the only way how the methods of furniture and wooden
products development were researched until recently. Despite the fact that standardized
furniture testing is not compulsory for producers in most cases, it is commonly implemented.
Numerical simulations have been applied by furniture industry in a limited way so far (Mirra
Office Chair [4]). The issue of strength design of furniture and various research methods is
rather comprehensively described by [2], [6] or [3]. The issue of Digital Image Correlation
(DIC) methodology in relation to a shape and deformation measurement is described e.g. by [7]
or [1].[5] employed DIC (3D) and numerical simulation to define material properties of veneer
composite structure laminate analysing a chosen shell of a chair. The objective of this study is
to assess behaviour of a flat pack construction of a chair using an optical DICmethod.
The construction of the chair was assembled from six parts, no glue was used. The chair
construction was mechanically loaded in furniture testing laboratory according to the Czech
standard (CSN EN 1728). The device loaded the seat with the force of 1300 N and the back
with the force of 450 N, at the points determined by the loading diagram. The values of
displacement in the horizontal and vertical direction for chosen points were assessed.
Figure 1: Tested chair in the laboratory.
86
RESULTS
The results can be summed up as follows:
 The tested chair construction shows the highest displacement in the back;
 The tested chair construction shows the largest strain in dovetail connections between the
backand the side and between the seat and the side;
 The maximum deviation of the observed surface was detected in the back of the chair.
It is possible to say that the DIC is easily utilizable and applicable to furniture testing due to
its relative simplicity and low requirements on employed devices, undemanding data
procession and data assessment realized by accredited laboratories or research institutes.
ACKNOWLEDGEMENT
This research was supported by the Internal Grant Agency of Faculty of Forestry and Wood
Technology, Mendel University in Brno – within the development project IGA No. 57/2013.
REFERENCES
[1] Cintrón R, Saouma V (2008) Strain measurements with the Digital Image Correlation system
Vic-2D. Civil Environmental and Architectural Engineering, University of Colorado
[2] Eckelman C (2003) Product engineering and strength design of furniture. Purdue University,
West Lafayette, Indiana
[3] Joščák P (1999) Pevnostné navrhovanie nábytku.Technical University in Zvolen
[4] Larder L, Wiersma J (2007) CEA takes a front seat. ANSYS Advantage, Volume 1, Issue 1
[5] Nestorović B, Skakić D, Grbac I (2011) Determining the characteristics of composite structure
laminae by optical 3D measuremtent of deformation with numerical analysis. Drvna Industrija
62(3):193-200. DOI: 10.5552/drind.2011.1103
[6] Smardzewski J (2004) Modelowanie półsztywnych wezłow konstukcyjnych mebli.
Wydawnictwo Akademii Rolnicznej im. Augusta Cieszkowskiego w Poznaniu, ISBN 83-7160343-6
[7] Sutton MA, Orteu JJ, Schreier HW (2009) Digital image correlation for shape and deformation
measurements Basic Concepts, Theory and Applications. Springer Springer-Verlag, Heidelberg.
87
EFFECT OF HEAT-TREATMENT OF FLAKES ON PHYSICAL AND
MECHANICAL PROPERTIES OF FLAKEBOARD
J.H. Kwon1,* & N. Ayrilmis2
1
Department of Forest Biomaterials Engineering, College of Forest and Environmental Sciences, Kangwon
National University,
200-701, Chuncheon, Republic of Korea
*
2
Department of Wood Mechanics and Technology, Forestry Faculty, Istanbul University
Bahcekoy, 34473, Sariyer, Istanbul, Turkey
INTRODUCTION
Wood modification by heat-treatment has been generally accepted as a possible way to
improve some characteristics of wood [1]. The main purpose for the heat-treatment between
approximately 150°C and 220°C is to achieve new material properties such as increased
biological durability and weather resistance, enhanced dimensional stability, reduced extractive
contents, increased heat insulating capacity, the possibility of controllable color changes, lower
equilibrium moisture content, which might prolong the service life of wood products [1-2].
Flakeboard generally has poorer dimensional stability than plywood or solid wood. This
precludes the use of flakeboards where they are exposed to high relative humidity [3].The
objective of this research was to determine the effect of heat-treatment temperature of flakes on
the physical and mechanical properties of flakeboard.
The average length, width, and thickness of Radiata pine (Pinus radiata D. Don) flakes used
in the experiments were 75–100 mm, 8.5–10 mm, 0.4 mm, respectively. The flakes were heat
treated at three different temperature, 150 °C, 170 °C, and 190 °C, for 2 h in a heating chamber.
Heat-treated and control flakes were sprayed with a 61.1 weight percent aqueous solution of
urea-formaldehyde resin to give a 10% adhesive content based on the oven-dry weight of wood
in the blender. The flakes were then formed into a 29 cm x 29 cm x 1 cm randomly oriented
mat and pressed at 2.8 MPa for 7 minutes between platens heated to 170 °C to produce 10 mm
thick flakeboards.
150 °C
170 °C 190 °C
Figure 1: Heat treated radiata pine flakes.
88
Prior to testing the specimens were conditioned to constant mass at a temperature of 23 °C
and a relative humidity of 65%. Some physical properties; weight loss, density, water
absorption (WA), and thickness swelling (TS), and mechanical properties; modulus of rupture
(MOR), modulus of elasticity (MOE) and internal bond (IB) strength of the produced
flakeboards were determined according to Korean Standard (KS) F 3104 (2002). 10 samples
weretaken foreach test.
RESULTS
The results of physical and mechanical properties are presented in Table 1. A slight
increment in the density of the boards was determined. The weight loss of the specimens
considerably increased with an increasing temperature. Weight loss of wood is one of the main
indicators of the degree of heat modification and is directly related to mechanical properties [2].
The higher weight loss resulted in lower MOR and MOE of flakeboards. This was because the
higher the weight loss, the more advanced the decomposition of the main chemical wood
compounds. The moisture content of the conditioned boards at 23 °C and a relative humidity of
65% decreased as the treatment temperature increased. The TS and WA of the specimens
significantly decreased with an increasing treatment temperature, in particular at 190 °C. This
was mainly attributed to the destruction of hemicelluloses, which reduce the hygroscopic cites
of wood. The bending properties of the specimens decreased with an increasing treatment
temperature. The primary reason for the lower bending properties is the degradation of
hemicelluloses, which are less stable to heat than cellulose and lignin. However, the IB
strength of the specimens improved with an increasing treatment temperature as compared to
the control specimens. This could be related to the decrement in the weight loss of the flakes
and thereby increment in the compression ratio in the flakeboard mat during the hot pressing.
Table 1: Physical and mechanical properties of flakeboards.
Panel
type
Treatment
temperature
[°C]
Physical properties
Mechanical properties
Weight Density
MC
TS
WA
MOR
MOE
IB
loss
[g/cm3]
[%]
[%]
[%]
[N/mm2] [N/mm2] [N/mm2]
[%]
A
Control
0.87
5.56
90.1 77.8
36.0
3869.5
0.14
B
150
5.23
0.93
5.50
83.6 69.5
36.0
3693.1
0.17
C
170
9.40
0.94
4.87
82.6 68.8
31.4
3567.8
0.19
D
190
11.0
0.95
4.76
59.5 62.6
24.5
2981.9
0.17
MC: moisture content. TS: thickness swelling. WA: water absorption. MOR: modulus of rupture. MOE: modulus
of elasticity. IB: internal bond strength.
CONCLUSIONS
The results showed that the water resistance and IB strength of the flakeboards were
improved by the heat-treatment of the flakes while the bending properties decreased.
According to the obtained results, the optimum heat-treatment condition for the flakes was
150 °C for 2 h.
REFERENCES
[1] Esteves BM, Pereira HM (2009) Wood modification by heat-treatment: A review.
BioResources 4:370-404
[2] Hill CAS (2006) Wood modification. Chemical, heat and other processes. John Wiley& Sons,
Chichester
[3] Youngquist JA.,Krzysik, Rowell RM (1986)Dimensional stability of acetylated aspen flake
board. Wood Fiber Sci 18:90-98
89
RECENT DEVELOPMENT IN THE CONTACT DRYING OF VENEER
Olli Paajanen
Aalto University, Department of Forest Products Technology
P.O.Box 16300 FI-00076 Aalto, Finland
ABSTRACT
Veneer drying is an important part of manufacturing veneer based composite products, such
as plywood and laminated veneer lumber (LVL). As the moisture content of green wood is
high and the end moisture content of the final product is low, large amount of energy is used to
remove the water. While a major part of the process energy (heat) can be produced by burning
the process residues, there is a need to reduce the energy use and manufacturing costs. The
demand and cost of biomass is increasing and environmental performance of wood products is
strongly dependent on energy use in manufacturing. For the Finnish wood product industry this
is especially important, as plywood is one of the main products, with a production of 1.16 Mm 3
in 2014 and also the share of exports is high, approx. 85% in 2013 [1]. The drying process also
has a major impact on veneer quality. Due to these reasons the drying process is developed
constantly.
The currently used veneer drying technology is based on convective heat transfer. It has
some shortcomings, such as veneer quality issues, overdrying and variation in moisture content
within and between veneer sheets. To solve these issues, alternative drying technologies have
been developed. These include e.g. radiofrequency (RF), vacuum, and contact (platen) drying.
The techniques have various advantages, such as efficient heat transfer, speed [2] or veneer
quality (e.g. flatness). Still there are shortcomings, which include for instance high energy
costs due to the use of electricity (RF, vacuum) and the fouling of press plates in platen drying.
There is also the issue of capacity: industrial dryers process large volumes of veneer quite
rapidly. The substituting technology must achieve the same at reasonable investment costs.
Due to combinationsof these issues the alternative technologies have not been introduced on
large scale manufacturing. While these challenges exist, there is a need and interest to develop
veneer drying.
An alternative veneer drying technology has been developed at Aalto University in Finland.
It utilizes conductive heat transfer, vacuum and temperature difference on the different sides of
the veneer. The device is a variation of a platen dryer: the veneer is placed between two plates,
but only the top one is heated. The other plate or supporting element has a metal wire web
surface, so that the water vapor can travel through it. Below the wire surface there is a cooling
section, a series of pipes with water circulation. The drying chamber is also sealed, so that
vacuum can be introduced. The combination of these features provides several advantages: the
direct contact with the heating plate ensures fast heat transfer; the wire section below the
veneer lets the water vapor into the cooling section where it condenses and the use of vacuum
lowers the boiling point and reduces the diffusion resistance of air. In practice, the device has
about 50% shorter drying time than traditional drying at the same temperature; especially the
free water is removed fast when vacuum is used [3]. With the use of vacuum it is also possible
to use lower drying temperatures than traditionally. The surface of the veneer is flat and
smooth and also other properties are comparable to conventionally dried veneer [4].
Recent experiments with the device have focused on the drying phenomenon, e.g.
temperature development during the drying process. These observations support the earlier
90
findings and provide more information about the process, but more work is needed to find
optimal parameters. The combination of process parameters, especially temperature,
compression pressure and vacuum, have an effect on veneer quality. High compression during
the drying sequence can have a similar effect on the veneer as the densification process, which
is used to modify the properties of the veneer. Although the focus of the development has been
on the drying process, its effect on veneer properties may provide new applications of the
technology.
REFERENCES
[1] Finnish Forest Industries (2015) Plywood manufacturing statistics
[2] Tschernitz JL (1985) Empirical Equations for Estimating Drying Times of Thick Rotary-Cut
Veneer in Press and Jet Dryers (No. FSRP-FPL-453). Forest Product Lab Madison
[3] Holmberg H, Lahti P, Paajanen O, Ahtila P (2009)An experimental study on drying times in a
contact drying of veneer. Proceedings of 8th World Congress of Chemical Engineering, 2327.8.2009, Montreal, Canada
[4] Paajanen O, Kairi M (2012) Results from experiments with a new contact drying technology.
Proceedings of the World Conference on Timber Engineering. 16-19.7.2012 Auckland, New
Zealand
91
Session IV
Wood Panels Composites and Processing
Poster Session
A NOVEL LOW-DENSITY SANDWICH PANEL MADE FROM HEMP
J. Selinger* & R. Wimmer
University of Natural Resources and Life Sciences
Gregor-Mendel-Straße 33, 1180 Vienna, Austria
*
INTRODUCTION
One drawback of conventional particleboards is their high weight at moderate mechanical
properties values (cf. [1]). Further, wood as a raw material has been facing temporary shortage
situations (cf. [2]), which poses the question for possible alternative resources. Here, hemp
shives are utilized for the development of low density particleboards with faces added to both
sides of the board. The hemp resource was obtained as the leftover fraction after hemp seed
production for hemp oil. The aim of this research was the development of a low-weight panel
made from hemp showing competitive mechanical performance. The aim was further to
develop a panel that is formaldehyde free and fully bio-based.
Hemp fibers and hemp shives were mechanically separated using a fiber-opening carding
machine (“Faserwolf”). While the shives were resinated and further pressed to particleboards
with a targeted density of 320 kg/m³, about 12% of the obtained fibres were used for nonwoven fleece production.
Core particleboard: The resination of hemp shives (average length 9 mm) was performed
with Acrodur® DS 3515, an aqueous dispersion of a styrene-acrylic polymer modified with a
polycarboxylic acid and a polyol as crosslinking component. Additionally, a casein adhesive as
well as a standard urea formaldehyde resin was used. The resinated shives were placed into a
framed box with 40 × 45cm in size, (fig. 1, left), then manually prepressed, and subsequently
hot-pressed.
Face layers: Hemp fibers were air-laid to a non-woven fleece at an area weight of 1250
g/m². Fleeces were reinforced with a needle-punching machine, with the needle bed having 40
pinholes/cm², and a punching depth of 20mm. Fibre fleeces were impregnated with epoxised
hemp seed oil (cf. [3]) at 30% loading rate, followed by hot-pressing at 180°C and 0.75 MPa
for 25 minutes, reaching a thickness of 0.7 mm.
Figure 1: Framed-box with resinated hemp shives (left); sandwich with hemp particleboard core layer, and
hemp non-wovens as faces added to both sides of the panel (right)
93
Face layers were glued onto both sides of the particleboard using the adhesive of the
individual panel type, at 100 g/m² (fig 1 right).
Compared to the single-layer hemp-shive particleboard, the modulus of elasticity was raised
up to 3.6 times due to the face layer additions. In fig. 2 the red line indicates the standard
requirements for particleboards (ÖNORM EN 312, 2003). Bending strength of the sandwich
particleboard was 3.2 times higher than the single-layer particleboard. With respect to the
standards all sandwich-particleboards met the required values. The casein-bonded panels
delivered results as good as the urea-formaldehyde bonded type. Internal bonding values (not
shown) also met minimum requirements.
Modulus of Elasticity [N/mm²]
2500
2000
1500
1000
500
0
Acrodur
one layer
Acrodur
three layer
Casein
one layer
Casein
three layer
UF
one layer
UF
three layer
Adhesives with and without additional top layer
Figure 2: Modulus of elasticity of the one-layer, and the sandwich (three-layer) hemp panel, using different adhesive
types
CONCLUSIONS
Through a sandwich construction, i.e. hemp-based particleboards with hemp-based nonwoven layers added as faces to both sides, an increase in mechanical properties up to 3.6 times
was achieved. This means, with only half of the density of a regular wooden particleboard, the
new hemp-made sandwich particleboard demonstrates the same level of performance. The
casein-bonded panel type delivered also a “formaldehyde-free”, and fully bio-based panel
version with hemp as a raw material. The new type of sandwich panel made of hemp could be
used for various lightweight construction purposes.
REFERENCES
[1] Wong ED, Zhang M, Wang Q, Kawai S (1999) Formation of the density profile and its effects
on the properties of particleboard. Wood Science and Technology, 33(4):327-340
[2] Wimmer R, Weigl M, Schöneberg S (2011) Particle boards made from hardwoods – what is the
significance? Peer-Review Proceedings of the International Scientific Conference on Hardwood
Processing, Blacksburg, Virginia, October 2011
[3] Wuzella G, Mahendran AR, Müller U, Kandelbauer A (2013) Thermal cure kinetics and
rheology of an epoxidized bioresin based on hempseed oil and its usage in hemp fiber
reinforced composites. Wood Carinthian Competence Center: Sankt Veit an der Glan
94
NEW INNOVATIVE PROCESS FOR NANOSCALE COATINGS ON
WOOD SURFACE USING ELECTROSPINNING TECHNIQUE
A. Kumar*, P. Ryparova, J. Tywoniak, P. Hajek
Czech Technical University in Prague, Faculty of Civil Engineering, Department of Building Structures
Thákurova 7, 16629 Prague 6, Czech Republic
*
e-mails: [email protected]
INTRODUCTION
Wood is most versatile natural material because of its fibrous nature and it has a variety of
uses. However, the susceptibility to dimensional changes and biodegradation by
microorganisms restrict the use of wood in fluctuating humidity conditions. The penetration
and absorption of water in the bulk can be controlled by the initial interactions of water with
the surface. Therefore, the protection of wood surfaces with a hydrophobic barrier layer is a
primary requirement [1]. There are several chemical hydrophobic surface treatments of wood
in use, including silylation, fluorination, and covalent grafting of silicone polymers. The solgel process has been successfully used to grow metal oxide nanoparticles on wood surface
including TiO2[2] and SiO2 [3].
In this paper we are introducing a new facile technology to create the nanofibers coating on
wood surface known as “roller electrospinning technology” also called Nanospider. This
technology was developed and patented by [4]. Figure 1 demonstrates the roller
electrospinning process. Nanospider consists of a rotating roller to spin fibers directly from the
polymer solution. This roller spinning electrode is partially immersed in the tank with the
polymer solution (Figure 1). A grounded collector electrode is placed at the top of the spinner.
Figure 2 shows the PVA/SiO2 nanofibers coated superhydrophobic wood surface and SEM
image of nanofibers coating on wood surface.
Figure 1: The schematic diagram of roller electrospinning process adopted from [4].
95
Figure 2: An optical image of nanofibers coated wood with water droplets and a SEM image of electrospun nanofibers
coated wood surface.
CONCLUSIONS
New innovative wood coating method was introduced in this work. The PVA/SiO2 based
superhydrophobic coating was introduced on wood surface in nanofibrous morphology.
ACKNOWLEDGEMENTS
This research work was supported by the European social fund within the framework of
realizing the project “Support of inter-sectoral mobility and quality enhancement of research
teams at Czech Technical University in Prague”, CZ.1.07/2.3.00/30.0034.
REFERENCES
[1] Samyn P, Stanssens D, Paredes A, Becker G (2014) Performance of organic nanoparticle
coatings for hydrophobization of hardwood surfaces.J Coat Technol Res 11(3):461-471
[2] Li J, Yu H, Sun Q, Liu Y, Cui Y, Lu Y (2010) Growth of TiO2 coating on wood surface using
controlled hydrothermal method at low temperatures. Appl Surf Sci 256(16):5046-5050
[3] Hsieh CT, Chang BS, Lin JY (2011)Improvement of water and oil repellency on wood
substrates by using fluorinated silica nanocoating. Appl Surf Sci 257(18):7997-8002
[4] Jirsak O, Sanetrnik F, Lukas D, Kotek V, Martinova L, Chaloupek J (2004). A method of
nanofibres production from a polymer solution using electrostatic spinning and a device for
carrying out the method. European Patent: EP 1 (673 493)
96
Second Day
Session I
Modification of Lignocellulosics
UNDERSTANDING DECAY RESISTANCE, DIMENSIONAL STABILITY
AND STRENGTH CHANGES IN ACETYLATED WOOD
R. M. Rowell
Professor Emeritus, University of Wisconsin, Madison, WI, USA
INTRODUCTION
With an increased awareness of the fragility of our environment and the need for durability
in wood products, new technologies have been developed to increase the service life of wood
materials. Issues of sustainability, carbon sequestration and performance converge in this
search for environmentally friendly methods of wood preservation. One method that has been
shown to greatly improve both wood stability and durability is acetylation [1].
WOOD-OH + CH3C(=O)-O-C(=O)-CH3 → WOOD-O-C(=O)-CH3 + CH3C(=O)-OH
Acetic Anhydride
Acetylated Wood
Acetic Acid
The reaction of wood with acetic anhydride produces a modified wood that greatly reduces
hygroscopicity [2]. The equilibrium moisture content of the reacted wood decreases as the level
of cell wall bonded acetyl increases [Table 1]. Both the fiber saturation point and the
equilibrium moisture content are reduced in a linear relationship to the level of acetyl weight
gain. This means that the reduction in moisture content is not dependent on where the
acetylation reaction takes place in the cell wall. Both the sorption of primary and secondary
water are reduced. The reduction of moisture sorption reduces the sorption and desorption of
environmental gasses such as formaldehyde. There is a greater difference in the sorptiondesorption isotherm (hysteresis) in acetylated wood as compared to non-acetylated wood. This
may be due to the increased time it takes for moisture to sorb into the acetylated cell wall.
Dimensional stability of the reacted wood also increases as the level of cell wall bonded
acetyl increases due to the esterification of the accessible hydroxyl groups in the cell wall
reducing hydrogen bonding with water and bulking the cell wall back to its green volume
[Table 1]. Dimensional stability is not 100% since the water molecule is smaller than the acetyl
group so water can access hydroxyl sites even when the wood is fully acetylated.
Resistance to fungal attack increases as the level of acetylation increases. The level of acetyl
needed to stop white-rot fungal attack (7–10%) is much lower than that needed to stop brownrot fungal attack (17–19%) [Table 1]. The mechanism of decay resistance in acetylated wood is
thought to be based on moisture exclusion due to the fact that the equilibrium moisture content
of a highly modified wood is too low to support fungal growth so the initial colonization does
not take place, i.e. no water molecules at the site of a glycosidic bond that the fungal enzymes
need for hydrolysis [3]. Another idea is that the mechanism is based on the modification of the
hemicellulose fraction in the cell wall. The hemicelluloses are the most hydroscopic polymer in
the cell wall and fungal attack may take place there first. The increase in fungal resistance is
not linear with the increase in acetyl content indicating that fungal resistance is due to more
than one type of hydroxyl substitution.
Table 1: Properties of acetylated pine.
WPG
FSP
0
6
10.4
15.7
21.1
45
24
16
14
10
EMC
30% RH
5.8
4.1
3.3
2.7
2.3
65% RH
12
9.2
7.5
6.5
4.3
Decay Resistance
Brown-rot
White-rot
61.3
7.8
34.6
4.2
6.7
2.6
3.2
<2
<2
<2
90% RH
21.7
17.5
14.4
10.1
8.4
WPG = Weight percent gain of acetyl, FSP = Fiber saturation point, EMC = Equilibrium
moisture content, RH = relative humidity, Brown-rot fungus = Gloeophyllum trabeum, Whiterot fungus = Trametes versicolor.
Strength properties are not significantly changed in acetylated wood and acetylation results
in greatly improved wet strength and wet stiffness properties [Table 2]. Wet stiffness in nonacetylated wood is greatly reduced due to the low Tg of the cell wall hemicelluloses.
Table 2: Strength properties of acetylated solid pine wood.
Sample
Dry
Strength
MOR
2
Pine
Acetylated
Pine
(19WPG)
N/mm
63.6
64.4
Wet
Strength
MOR
2
N/mm
39.4
58.0
Dry
Stiffness
MOE
2
N/mm
10,540
10,602
Wet
Stiffness
MOE
2
N/mm
6760
9690
CONCLUSIONS
In acetylated wood, reductions in hygroscopicity are due to substitution of hydroxyl groups
with an acetyl group which is less hygroscopic as compared to the hydroxyl group. Increased
dimensional stability in acetylated wood is due to the bulking of the cell wall back to its
original green dimensional so the cell wall cannot expand very much more because of the
elastic limit of the cell wall has not been exceeded. Decay resistance of acetylated wood is due
to the lowering of the cell wall moisture content becoming too low to support fungal attack so
the initial enzymatic attack does not take place. Strength properties are not significantly
changed in acetylated wood and acetylation results in greatly improved wet strength and wet
stiffness properties.
REFERENCES
[1] Rowell RM, Tillman A –M, Simonson R (1986) A simplified procedure for the acetylation of
hardwood and softwood flakes for flakeboard production. J Wood Chem Tech 6(3):427-448
[2] Rowell RM (2005) Chemical modification of wood. Chapter 14. In: Handbook of Wood
Chemistry and Wood Composites R.M. Rowell, ed. Taylor and Francis, Boca Raton, FL. 381420
[3] Ibach RE and Rowell RM (2000) Improvements in decay resistance based on moisture
exclusion. Mol Cryst Liq Cryst 353:23-33
99
INCREASE IN THE RESISTANCE TO BIODEGRADATION OF BLACK
POPLAR WOOD BY THERMOMODIFICATION
A. Fojutowski*, A. Noskowiak, A. Kropacz
Wood Technology Institute
Winiarska str.1, PL 60 654 Poznań, Poland
*
e-mail: a_noskowiak@ itd.poznan.pl
e-mail: a_kropacz@ itd.poznan.pl
INTRODUCTION
In Europe, implementation of the Biocide Directive and the Directive on emissions of
volatile organic compounds significantly reduced the applicability of biocides in wood
preservation, in order to reduce the risk to human health and the environment. Esterification of
wood, thermo- or thermo-oil modification of wood are considered safer methods of improving
the durability of wood, from the toxicological and environmental points of view. It is an
alternative to biocides usage to increase wood durability [1]. For the period 2008-2014 we
carried out our own work on the thermal and thermo-oil wood modification, in cooperation
with industrial plants. The study included wood species commonly used in the construction
industry, such as pine, spruce, beech, but also species that will only be able to find wider
application through modification, such as birch, alder or poplar (EN 350-2, EN 599-1). We
found improvements of wood performance, especially dimensional stability and water
resistance, resulting from the modification range. Additionally, we observed in varying degrees,
but clearly greater resistance of thermal and thermo-oil-modified wood to wood-decaying fungi
from the class Basidiomycetes while a lack of increased resistance (or only to a very limited
extent) to filamentous fungi (moulding and soft rot) [1,2]. In construction industry increased
interest in the use of wood materials for the construction of terraces. The thermo- or thermooil-modified wood, can respond to this application. One of the most destructive factors in
contact with the ground are filamentous fungi that cause soft rot of wood, as well as fungi
causing brown rot and white rot of wood. The field tests of thermomodified wood in ground
contact will be carried out with the purpose of assessing the application in such conditions. It is
assumed that these studies should be extended for at least five years and create the opportunity
to conduct further studies of the wood in ground contact, as a permanent element of the
assessment of the durability of developed products. Aim of this study was to identify durability
of natural and thermally modified black poplar wood (Populus nigra L.) in ground contact after
one year of exposition.
MATERIALS AND METHOD
As a model material we prepared twin (directly adjacent on sides measuring 500 × 50 mm)
samples sized 500 (L) × 50 (R) × 25 (T) mm of natural and thermomodified poplar wood. The
modification was carried out in an industrial plant, in an open system under conditions of
temperature to 210°C, in air. Before placing in the soil, the samples were planed, selected to
eliminate cracked and warped samples, and air-conditioned in the standard climate, nominally
at 20±1° C and 65±5% relative humidity. Tests were carried out starting in 2013 acc. to
standard commonly used in Europe (EN 252) and using the field test established by the Wood
Technology Institute from 2010 in the Jarocin Forest District in cooperation with the Regional
Directorate of State Forests in Poznań.
RESULTS
The minimum and the maximum daily temperatures (Fig. 1) in the observation period were 16.0 ° C and +33.5°C, respectively. The average value of the minimum temperature in the
observed period amounted to +7.3°C, and the average maximum temperature to +15.3°C.The
average precipitation in the observed period referenced to days with precipitation was 5.7 mm
H2O. Total precipitation in the observed period was 385 mm H2O. This means the precipitation
was lower than the theoretical average precipitation in such a period - approx. 570 mm H2O.
Natural poplar wood has been strongly destroyed - rating 2.93 (EN 252: medium attack rating 2, and strong - rating3), including 3 broken samples, and the depth of softening generally
ranged from 8–15 mm, indicating advanced wood decay (Table 1). The thermomodified poplar
wood manifested light attack, the average rating of 1.10, the depth of the softening of less than
1 mm in 93% of the samples. For comparison, the rating of tested natural Scots pine sapwood
amounted to 1.30 - i.e. slightly more than attack known as light attack (rating 1). Softening of
the wood did not exceed a depth of 5 mm, and 51% of pine samples were characterized by
softening to a depth less than 1 mm. Most samples of natural and modified poplar wood
showed the presence of hyphae, while molds occurred mainly on natural wood. There was no
occurrence of algae; but the surface of natural poplar wood showed gathered microparticles of
wood, probably caused by wasps. All samples turned grayish, cracks occurred on the end
surfaces (transverse-sections) of the samples.
Table 1: The assessment of attack caused by microorganisms after 1 year exposition on test stakes - EN 252 test.
Rating of black poplar
Natural
Mean
2,39
Minimum
2,0
Maximum
4,0
Minimum
1,0
Thermomodified
Mean
1,10
Maximum
2,0
Temperature and precipitation 5.12. 2014- 06.10 .2014
days/date
31.08.2014
02.06.2014
04.03.2014
Temperature [oC]
temp. min
temp. max
Figure 1: Example of the figure.
CONCLUSION
Thermomodified black poplar wood decomposed in ground contact slowly, compared to
natural black poplar wood and after one year of exposure in the ground showed slight,
especially initial, symptoms of degradation similar to that of Scots pine sapwood.
ACKNOWLEDGEMENTS
The work was financially supported by Ministry of Science and High Education as Wood Technology
Institute research projects ST-3-BOD/2013/N and ST-2-BOD/2014/K
101
REFERENCES
[1] Fojutowski A., Kropacz A., Noskowiak A. (2009): The resistance of thermo-oil modified wood
against decay and mould fungi.Doc. No. IRG/WP/09 – 40 448, 11p., Stockholm, Sweden
[2] Militz H., Callum H. (2005) Wood modification: Processes, Properties and Commercialisation,
Second ECWM Conference Materials, Göttingen 2005
WEATHERING STABILITY OF PF-TREATED VENEER PRODUCTS
FROM BEECH WOOD
S. Bicke* & H. Militz
Georg August University of Göttingen, Wood Biology and Wood Products, Burckhardt-Institute
Büsgenweg 4, 37077 Göttingen, Germany
*
INTRODUCTION
This work deals with the evaluation of the weathering stability of PF-modified wood
composites of European beech (Fagus sylvatica) veneers. It is known that cell wall
modification with low molecular weight phenol formaldehyde can bring dimensional stability
[1] to the wood and increases the durability against fungi attack [2], but phenol as well as
lignin can be degraded by UV-light [3]. However, the benefits from PF-modification seem to
increase the weathering performance. For the estimation of this effect a field test and an
artificial laboratory test were performed. In both tests the focus was on the dimensional
stability, water uptake and crack performance.
METHODS
For the production of the samples a variety of low molecular weight PF impregnation resins
were used in different concentrations for the impregnation of the rotary cut beech veneers. The
impregnation was done in an autoclave under vacuum and subsequent overpressure. For the
board production 8 plies were assembled mainly parallel with the grain, whereat the second
and the seventh veneer were oriented perpendicularly. To achieve different grades of
densification several pressing pressures were used which led to different raw densities. The
performance of samples with a relatively low resin loading and a low densification was of
special interest. The samples were exposed to the weathering tests majorly without a coating.
The performance of coatings was only tested for a single variant of treatment. Whereas the lap
test lasted 5 weeks, the field test is still running and is giving therefore intermediate (9 months)
results.
RESULTS
Evaluation of the data showed that the PF-treatment gave weathering stability to all of the
variants tested, but results differed from the test method. Concerning the dimensional stability,
the densification in combination with the resin loading (Weight Percent Gain, WPG) had the
greatest influences, whereas the resin type played an inferior role when proper cell wall
penetration was achieved.
103
Figure 5: Water uptake of Beech-LVL during 9 months field exposure – treated with one type of PF-resin, different
WPG and pressing pressure.
Figure 6: Thickness swelling uptake of Beech-LVL during 9 months field exposure – treated with one type of PF-resin,
different WPG and pressing pressure.
CONCLUSIONS
It can be concluded that the modification with low molecular weight phenolic resin by
impregnation under vacuum und subsequent pressure increases the weathering stability of
veneer products from beech wood. The extent of the material improvement can be attributed
not only to the resin type, but also the WPG and pressing parameters, or the density of the final
product. Concerning the WPG, it was found that 30% can compete with 60% and consequently
such high material inputs can be avoided.
REFERENCES
[1] Gabrielli C, Kamke F (2010) Phenol–formaldehyde impregnation of densified wood for
improved dimensional stability. Wood Sci Technol44(1):95-104
[2] Furuno T, Imamura Y, Kajita H (2004) The modification of wood by treatment with low
molecular weight phenol-formaldehyde resin: a properties enhancement with neutralized
phenolic-resin and resin penetration into wood cell walls. Wood Sci Technol 37(5):349-361
[3] Evans DP, Gibson KS, Cullis I, Liu C, Sèbe G (2013) Photostabilization of wood using low
molecular weight phenol formaldehyde resin and hindered amine light stabilizer. Polym
DegradStabil 98(1):158-168
INFLUENCE OF REACTION CONDITIONS ON THE CRYSTALLINE
FORM OF HYDROTHERMALLY DEPOSITED TIO2 ON SURFACES OF
SPRUCE WOOD
P. Pori1, B. Orel2, A. Vilčnik1, A. Sever Škapin3, M. Petrič4,*
1
Chemcolor Sevnica, d. o. o.
Dolnje Brezovo 35, 8283 Blanca, Slovenia
2
National Institute of Chemistry
Hajdrihova 19, 1000 Ljubljana, Slovenia
3
Slovenian National Building and Civil Engineering Institute
Dimičeva ulica 12, 1000 Ljubljana, Slovenia
4
University of Ljubljana, Biotechnical Faculty
Jamnikarjeva 101, 1000 Ljubljana, Slovenia
*
INTRODUCTION
Weathering effects of wood can be diminished by application of surface coatings containing
pigments. Recently, there have been reports on inorganic nanoparticles, applied in transparent
finishes instead of pigments. Another option to protect wood with nanoparticles is their
hydrothermal deposition on surfaces of wood to be coated. Most commonly, TiO2
nanoparticles are applied. The most frequent crystalline forms of TiO2 are the rutile and the
anatase. The rutile form is prominent by its UV absorbing properties, while the anatase form is
used for photocatalytic purposes. So, it is important to find such parameters of hydrothermal
deposition process that would lead to deposition of the rutile type TiO2 on wood surfaces.
TiO2 particles were deposited on surfaces of Norway spruce wood samples by the low
temperature hydrothermal deposition. Samples impregnated with distilled water were treated
with a solution of sodium dodecyl sulphate. The samples were then put into a reactor
containing 0.5 mol/l aqueous solutions of TiCl4 with different HCl concentrations. The
syntheses were carried out at different temperatures from 25 °C to 90 °C and at variable
concentrations of HCl from (0 mol/l to 1 mol/l). The surfaces with the TiO2 nanodeposits were
investigated by FT-Raman spectroscopy and by scanning electron microscopy (SEM).
The presence of TiO2 on wood was confirmed on the FT-Raman spectra (Figure 1) in the
spectral range between 700 and 100 cm-1, in accordance with the literature reports [1]. The
band at 157 cm-1 (A1 and B1 in Fig 1) was assigned to the anatase form [1]. The bands
assigned to the rutile form (608 cm-1 and 438 cm-1) [2] appeared when the reaction was carried
out at different conditions (Fig 2). The differences between the anatase and the rutile crystals
were also clearly seen on SEM micrographs of variously prepared samples.
105
157
1
625
A 1 (ABSORBANCE)
A1
B1
P-SDS
PICEA
0
700
600
200
100
A (1/CM)
438
157
C0
C1
C2
C3
C4
PICEA
247
1
608
C 0 (ABSORBANCE)
Figure 1: Parts of FT-Raman spectra, confirming the presence of TiO2 on the samples, treated at 25 °C (0.01 mol/l HCl,
A1) and 50 °C (0.01 mol/l HCl, B1). Untreated spruce wood is labelled as “PICEA” and wood, treated only with the
solution of SDS as “P-SDS”.
145
0
700
600
500
400
300
200
100
A (1/CM)
Figure 2: Parts of FT-Raman spectra of the samples treated at 75 °C (C), showing the influence of the HCl concentration
in the treatment solution, and of the control (PICEA) sample.
CONCLUSIONS
The amount of deposited TiO2 increased with the treatment temperature, and it was
substantial at the temperatures of 75 °C or higher. The largest portions of the rutile, UV
protecting form, were obtained at 75 °C, without HCl or when 1 mol/l HCl was mixed with the
TiCl4 treatment solution.
ACKNOWLEDGMENT
The operation was partially financed by the EU, European Social Fund. The operation was
implemented in the framework of the Operational Programme for Human Resources,
Development for the Period 2007-2013, Priority axis 1: Promoting entrepreneurship and
adaptability, Main type of activity 1.1.: Expert and researchers for competitive enterprises. The
research was supported also by The Slovenian Research Agency (the research programme P40015 »Wood and lignocellulosic composites«)
REFERENCES
[1] Bertoni G, Beyers E, Verbeeck J, Mertens M, Cool P, Vansant EF, Van Tendeloo G (2006)
Quantification of crystalline and amorphous content in porous TiO2 samples from electron
energy loss spectroscopy. Ultramicroscopy 106:630-635
[2] Liu LG, Mernagh TP (1992) Phase-transitions and raman-spectra of anatase and rutile at highpressures and room-temperature. Eur J Mineral 4:45-52
UNEVENLY DISTRIBUTED THERMAL MODIFICATION OF WOOD:
PRELIMINARY STUDY – DENSITY PROFILES
P. Čermák
ABSTRACT
Thermally modified timber has excellent properties suitable for outdoor application.
Therefore, nearly all of the thermally modified timber available on the market is used for such
applications, i.e. exterior trim, siding, decking and flooring. The main disadvantage of
thermally modified wood is its decrease in mechanical properties. The decrease is influenced
by used species, applied time and temperature of treatment. As a matter of this fact, thermally
modified wood has a very limited application for structural purposes.
The mass loss behavior of wood is one of the most important parameters to be considered
when applying any thermal modification technology. It is considered an indicator of the degree
of modification achieved and also quite often of the quality of modification. The motivation of
present study was to produce material with unevenly distributed thermal modification across
the wood cross section, using parameters that will guarantee that only surfaces of modified
wood are affected. This would bring also unevenly distributed properties (continuously), i.e.
thermally modified surfaces with better dimensional stability, bio-durability, but unchanged
mechanical properties in the middle section of wood.
Therefore, specimens of dimensions of 65 × 65 × 500 mm3 from beech wood (Fagus
sylvatica L.) and 95 × 95 × 500 mm3 spruce wood (Picea abies L. Karst.) were thermally
modified using a small scale laboratory heat treatment chamber. Thermal modification at
160°C and 200°C was applied for various time exposures. The specimens were taken out from
the chamber after 15, 30, 60, 120 and 240 min of exposure. As an indicator of degree of
modification, a measurement of density profiles was used in certain positions of the cross
section. The density profiles were measured by means of densitometer (X-Ray Denselab). The
density profiles were measured in different sample length and compared with reference. The
results should provide the first step in investigation of locally or unevenly modified wood, with
purpose of using it in structural applications.
Figure 1: Thermal modification process – temperature schedule and time intervals of specimens exposure.
107
ANTIFUNGAL EFFECT OF COPPER AND SILVER NANOPARTICLES
AGAINST WHITE-ROT AND BROWN-ROT FUNGI
P. Pařil1,*, J. Baar1, R. Prucek2, L. Kvítek2
1
*
2
Palacky University in Olomouc, Faculty of Science, Department of Physical Chemistry
17. Listopadu 12, 77146 Olomouc, Czech Republic
INTRODUCTION
Nowadays, there is a great boom in nanotechnology. Nanoparticles are used in many
industrial products which are applied in medicine, cosmetics, automotive industry, etc. Large
specific surface area and high reaction activity are very attractive properties for a lot of
applications. Nanoparticles also have a great potential for wood protection industry, especially
in the time of substituting demands of currently used substances (creosote, CCA, etc.).
Silver and copper nanoparticles are well-known for their biocide properties which improve
the wood durability. There are also some other applications, like prevention of leaching in
otherwise soluble biocides or altering treatability properties such as penetration and biocide
distribution. Nevertheless, we must keep in mind the potential environmental and health risks and
the risk governance recommendations [2].
Samples treated with nanocopper (leached and unleached) showed a significant inhibition of
mass loss (less than 10%) after exposure to Gloeophyllum trabeum (brown-rot fungi) and
Trametes versicolor (white-rot fungi). Nanocopper showed leach resistance compared to their
soluble copper oxide [3].
Mass loss of Paulownia treated with nanosilver and nanocopper aqueous dispersion (400
ppm) was less than 3% and this is supported by the differences in SEM photographs of the
undecayed and decayed treated wood [1].
MATERIAL, METHODS AND RESULTS
The impregnation was conducted using the laboratory vacuum-pressure impregnation plant.
Specimens were impregnated by two kinds of solution (copper and silver nanoparticles) with
two different concentrations (1000 and 3000 ppm). Each specimen was impregnated by
vacuum at 20 kPa for 120 min.
The decay tests were performed according to standard EN 113. Two fungi were used for the
determination of nanoparticles protection efficiency – white rot fungi (Trametes versicolor) for
treated beech samples and brown rot fungi (Poria placenta) for treated pine sapwood samples.
The fungicidal efficiency of the treatment was estimated using the mass loss (ML) caused by
fungi degradation.
Copper and silver amount in leachates collection were analysed and expressed as mg∙g-1.
35
30
Mass loss (%)
25
20
15
10
5
control
L B Ag 3g
Un B Ag 3g
L B Ag 1g
Un B Ag 1g
L B Cu 3g
Un B Cu 3g
L B Cu 1g
-5
Un B Cu 1g
0
Figure 1: Durability effect of beech treated with nanoparticles against Trametes Versicolor.
35
30
Mass loss (%)
25
20
15
10
5
0
Figure 2: Durability effect of beech treated with nanoparticles against Poria Placenta.
-5
CONCLUSIONS
Un B Cu 1g Un B Cu 3g Un B Ag 1g Un B Ag 3g
control
L B Cu 1g
L B Cu 3g
L B Ag 1g
L B Ag 3g
 Nanosilver treatment shows very low mass losses (under 3%) and high efficiency against
Trametes Versicolor fungi for leached and unleached beech but very low efficiency
against Poria Placenta decaying.
 Leached beech treated with nanoparticles has higher mass losses than unleached for both
fungi.
 Leachate from pine samples contains more copper and silver than from beech samples.
Amount of copper in leachate is higher than silver amount.
REFERENCES
[1] Akhtari M, Arefkhani M (2013) Study of microscopy properties of wood impregnated with
nanoparticles during exposed to white-rot fungus. ISSN 2306-7527
[2] Clausen CA (2007) Nanotechnology: Implications for the wood preservation industry. 38 th
Annual Meeting Jackson Lake Lodge, Wyoming, USA, 20-24 May 2007, IRG/WP 07-30415
[3] Kartal SN, Green F, Clausen CA (2009) Do the unique properties of nanometals affect
leachability or efficacy against fungi and termites? Int Biodeter Biodegr 63:490-495. doi:
10.1016/j.ibiod.2009.01.007
109
BONDING STRENGTH OF AMMONIFIED BEECH VENEER
V. Šprdlík1,*, S.Mihailović1, M. Brabec2, H. Klímová2
1
Mendel University in Brno, Faculty of Forestry and Wood Technology, Department of Furniture, Design
and Habitat
*
2
Mendel University in Brno, Faculty of Forestry and Wood Technology, Department of Wood
ScienceZemědělská 3, 61300 Brno, Czech Republic
INTRODUCTION
Furniture design helps to find and show possibilities of material. Here in this study, an
experimental stool is presented and the maximal bending angles usable in design of seating
furniture are shown. This study is focused on bonding properties of ammonified beech veneer.
The main purpose of ammonia treatment is to produce modified wood which imitates the
appearance of exclusive dark coloured wood species. This material is often used for furniture
and flooring systems. The most often modified wood is European beech (Fagus sylvatica,
L.)[1]. Ammonia treatment causes significant increase in hygroscopicity. Moisture absorption
of ammonia modified wood is higher than that of natural wood which negatively affects the
bonding strength[2]. The wood bonding process becomes more complicated due to the
anisotropic behaviour and highly variable surface of wood. Structures of wood differ from
species to species, thus the interaction between wood and adhesive is very difficult to evaluate
[3].
The stool itself is designed as a spring-like form, which gives a user option to change
position and allows him/her to swing. This feeling is relaxing and it can be compared to a
movement of a child cradle. A plywood structure was chosen because of the composite
behaviour of the material.
Bonding strength of ammonia treated veneer
Two groups of ammonified samples were used: freshly modified and 30-day conditioned.
After cooling, samples were divided into 6 groups – 36 samples for each adhesive. Polyvinyl
acetate (PVAC), polyurethane (PUR) and urine formaldehyde (UF with ammonium chloride as
a hardener) were used for gluing. According to standard ČSN EN 205 – glued area was 10 x 20
mm. Shear strength testing was performed on universal testing machine Zwick Z100, process
and evaluation of results was done in testXpert software. The calculation of shear strength of a
bonded joint was calculated by the following equation:
T=
Fmax
l.B
,
whereFmax is the maximum force, N; B is the width of tested bonded surface, mm; l is the
length of the tested bonded surface, mm.
RESULTS
The following table shows the differences between the bonding strength of freshly
ammonified, ammonified-conditioned and reference samples of beech veneer. There is a
significant variety of values mainly for PUR and PVAC adhesives. The bonding strength of
freshly modified veneers is almost twice as high compared to reference samples. This can be
caused by ammonia as an alkaline substance which changes surface roughness and enables the
adhesive to create a stronger bond.
Table 1: Bonding strength of ammonified beech veneer
Adhesive/
condition
Nr. of
samples
UF/old
UF/fresh
PVAc/old
PVAc/fresh
PUR/old
PUR/fresh
PUR reference
PVAc reference
UF reference
18
18
18
18
18
18
18
18
18
Maximal
stress
[MPa]
5,12
3,39
9,58
8,44
10,19
9,59
5,43
6,35
5,63
Standard
deviation
0,78
0,44
0,85
0,58
0,99
0,74
0,58
0,5
68
Coefficient Failure
of
of
variation
sample
15,21
wood
13,01
bondline
8,89
bondline
6,86
wood
9,68
wood
7,74
wood
10,77
wood
7,82
wood
12,14
wood
Decrease in
strength [%]
- 33,8
- 11,9
- 5,9
CONCLUSIONS
 Bonding strength of PUR adhesive increased in the case of freshly modified veneer by
43%, in the case of conditioned samples even by 47%. Failure of samples occurred in
wood.
 Bonding strength of PVAC adhesive increased in the case of freshly modified veneer by
25%, in the case of conditioned samples even by 34%. Failure of samples occurred in
wood of the fresh samples, and in the bondline of the conditioned samples.
 In the case of UF adhesive, the bonding strength of the conditioned samples remained the
same, in fresh samples a decrease occurred (- 40%).
REFERENCES
[1] Weigl M, Pöckl J, Grabner M (2009) Selected properties of gas phase ammonia treated wood.
Eur J Wood Prod67:103-109
[2] Minelga D, Ukvalbergiené K, Baltrušaitis A, Balčiūnas G (2013) Adhesion Properties between
Polyvinyl Acetate Dispersion and Ammonia Modified Oak Wood. Mater Sci19(2). doi:
10.5755/j01.ms.19.2.4433
[3] Frihart CR (2005) Adhesive Bonding and Performance Testing of Bonded Wood Products.
Journal of ASTM International 2(7). doi: 10.1520/jai12952
111
THE EFFECT OF THE PROCESS PARAMETERS OF THERMAL
MODIFICATIONS ON THE PHYSICAL AND MECHANICAL
PROPERTIES OF WOOD
F.P. Fodor*, B. Pozsgay, R. Németh
H-9400 Sopron, Bajcsy-Zsilinszky str. 4, Hungary
*
INTRODUCTION
The demand for the so-called Thermowood or Thermally Modified Timber (TMT) has
increased highly in the past years. The reason is that the modification process makes the
properties of the material more advantageous, like: aesthetics, durability, dimensional stability,
hygroscopicity, resistance to microbiological attacks, smaller equilibrium moisture content
(EMC). Our aim was to examine some properties (density, moisture content, modulus of
rupture, modulus of elasticity) of the materials which were produced/treated on different
industrial sites with different techniques.
Planks were delivered to our laboratory from two industrial sites.
One industrial partner performed the thermal modification of spruce (Picea abies Karst.)in
the presence of nitrogen medium, with permanent (marked as 11) and changing (marked as 12)
pressure.
The other did intensive (marked as 21) and careful (marked as 22) steaming of spruce(Picea
abies Karst.), beech (Fagus sylvatica L.), and ash (Fraxinus excelsior L.).
Table 1: Process parameters of the treatments in nitrogen gas medium
Pre-vacuum:
Nitrogen filling:
Heating:
Temp. maintenance:
Cooling:
Conditioning:
11
nitrogen gas medium, permanent pressure
from 0 to 0.6 bar in 10 minutes
permanent pressure
from 0.6 to 3.5 bar in 2 minutes
up to 170°C in 160 minutes
8 bar permanent pressure for 105 minutes
from 3.5 to 8 bar (linearly)
down to 80°C in 150 minutes
12
nitrogen gas medium, changing pressure
from 0 to 0.6 bar in 10 minutes
changing pressure
from 0.6 to 3.5 bar in 2 minutes
up to 170°C in 160 minutes
1 - 3 bar changing pressure for 105 minutes
between 1 - 3 bar (changing, nonlinear)
In the case of permanent pressure, the cooling process is more intensive (from 170°C to
80°C) which may cause cracks in the material. The changing pressure is probably due to an
open system where the degradation products (like acetic acid) can leave the medium, this way
they will not degrade the wood structure.
Table 2: Process parameters of steaming procedures
Pre-vacuum:
Steaming:
Heating:
Temp. maintenance:
Cooling, conditioning:
21
Intensive steaming
150 mbar pressure for 30 minutes
1 bar pressure, up to 100°C, for 2 hours
10
minutes
up to
170°C in 7 hours
7 bar pressure for 1 hour
11 hours long (probably down to 20°C)
22
Careful steaming
150 mbar pressure for 30 minutes
1 bar pressure, up to 100°C, for 2 hours
10
minutes
up to
155°C in 9 hours
5 bar pressure for 4 hours
13 hours long (probably down to 20°C)
In the case of intensive steaming, splits and crack may occur more often because of the
sudden temperature change. The more careful steaming process should give better properties
because of the smaller change in temperature and pressure and the longer heating time,
ensuring the wood’s polymer system to have a longer adaptation time. We can presume that the
material will be more brittle and it will have smaller EMC and density.
The test pieces’ dimensions were: 20×20×300 mm (T×R×L). From these specimens the
MOR, MOE, density and moisture content were determined. All in all, there were 60
“permanent pressure” specimens (11), 76 “changing pressure” specimens (12), 100
“intensively steamed” specimens (21) and 46 “carefully steamed” specimens (22).
Unfortunately due to the modification process, cracks and heart shakes occurred which led to
small yield (~43%). The specimens were put in a climate chamber at 20°C temperature, 65%
relative humidity.
RESULTS
Table 3: Results for treated spruce, beech and ash
Wood species
Thermo spruce
Thermo beech
Thermo ash
Categories u [%]
ρn [kg/m3]
σn [MPa] σ12 [MPa] En [MPa] E12 [MPa]
11
6.68
515
53
28
7653
5827
12
6.86
519
79
41
8336
6347
21
7.19
528
63
33
8082
6154
22
7.74
536
78
41
5594
4260
Literature
12
330-470-680
49-78-136
7300 - 11000 - 21400
21
7.08
722
72
38
9444
7191
22
7.29
791
107
56
11080
8437
Literature
12 540 - 720 - 910
74 - 123 - 210
10000 - 16000 – 18000
21
6.02
667
56
29
9587
7298
22
7.09
627
68
36
7017
5343
Literature
12 450…690…860
58…105…210
4400…13400…18100
CONCLUSION
Due to thermal modification the wood structure changed which was verified by our results.
The change of EMC proves the modification of the chemical structure and the MOR is in
connection with the microstructure (cell wall cracks and cell collapses). The EMC of treated
wood decreased to approx. 6-7%. The smallest decrease can be observed in the case of the
“carefully steamed” wood where there is lower temperature (155 °C) and longer conditioning
time (13 hours).
The density was at about the average of the literature data which is because of the dual
effect of modification. On the one hand the wood will lose weight, on the other hand it will
densify.
The specimens which were treated in changing pressure (open system) have better MOR
and MOE results because of the lack of degradation products.
113
Session I
Modification of Lignocellulosics
Poster Session
COMPARING THE VOC EMISSIONS OF HEAT TREATED WOOD
WITH AND WITHOUT FINISHING
P. Čech* & D. Tesařová
*
INTRODUCTION
Heat-treated wood is a popular decoration material and it is used in floor, wall, and ceiling
materials and in furniture.
Heat treatment affects all the wood components, i.e., cellulose, hemicelluloses, lignin, and
extractives. Emissions and degradation products of wood differ according to wood species.
Especially, differences can be detected between the hard- and softwood, which have different
cell types [1].
Hemicelluloses usually crack down thermally easier than cellulose or lignin because of their
heterogeneous structure and lack of crystallinity. Degradation of hemicelluloses occurs
intensively at 200-260 °C. Aliphatic carboxylic acids (mainly formic and acetic acids) are the
major volatile degradation products formed duringthe heat treatment [2, 3]. On the other hand,
large amounts of aceticacid were detected even from native wood samples [4]. Smaller
emissions of acetic acid were observed fromspruce than from hardwood due to greater number
of acetyl groupsin hardwood hemicelluloses. In addition, increased emissions offurfural from
ash, beech, maple, and spruce were detected due tothermal treatment, which was interpreted to
be caused by degradationof hemicelluloses. On the other hand, the emissions of theprevailing
aldehydes in natural wood, pentanal and hexanal decreased during thermal treatment [4].
EXPERIMENTAL
The tested wood (spruce Picea abies) obtained from KATRES company Ltd., Czech
supplier of heat-treated wood, was investigated. The pre-dried wood samples were modified at
180 C and 200 C in a heat treatment process.
Samples were taken from the normal manufacturing process, wrapped in aluminium foil and
delivered to the test laboratory. The wood was cut into pieces (sizes: 740 x 40 x 1mm) and put
into the test chamber. As emission rate of VOCs also depends on age, the samples were put
into the chamber as soon as possible after the delivery from the plant. The chosen heat treated
wood in 180°Cand 200°C were finished by water borne lacquers. In the present study, air
samples were collected continuously onto the Tenax TA until the required amont of the testing
days was obtained.
115
RESULTS
1061
1100
1000
883
Concentration [μg.m-3]
900
865
800
700
500
612
584
600
580
389
400
322
300
200
100
181
123
65
43
35 3 4
39
15 2 2
49
14 2 6
0
3
24
time [h]
72
Furfural_180 °C
Furfural_200 °C
Phenol_180 °C
Phenol_200 °C
672
Figure 1: Comparison of VOC emissions from Norway Spruce (thermowood) in 180 °C and 200 °C after finishing by
water borne lacquer.
CONCLUSIONS
 Heat treated wood from Norway spruce emitted more concentrations of furfural and
Phenol than untreated wood (natural wood).
 Heat treated wood form Norway spruce emitted more concentrations of furfural and
Phenol before finishing.
 Thermowood after finishing (water born lacquer) emitted very high concentration of
Butoxy-ethanol.
 Wood modified by heat treated process in 180 °C emitted more concentration of VOC
emissions than that processed in 200 °C.
REFERENCES
[1] Sjöström, E(1993) Wood chemistry. Fundamentals and Applications, second ed., Academic
Press, Inc., San Diego, pp. 1-293
[2] Kotilainen, R (2000) Chemical changes in wood during heating at 150–260 °C. Doctoral thesis,
University of Jyv.askyl.a, Department of Chemistry, Research Report No. 80, 57pp
[3] Sundqvist B, Karlsson O, Westermark U (2006) Determination of formic-acid and acetic acid
concentrations formed during hydrothermal treatment of birch wood and its relation to colour,
strength and hardness. Wood Sci Technol 40:549-561
[4] Peters, J, Fischer, K, Fischer, S (2008) Characterization of emissions from thermally modified
wood and their reduction by chemical treatment. Bioresources 3:491-502
116
THE EFFECT OF MICROWAVE PLASTICIZATION AND
DENSIFICATION ON DENSITY AND DENSITY PROFILE
V. Koiš*, J. Dömény, J. Tippner
*
INTRODUCTION
Wood structure and the chemical components contained within need to be plasticized before
wood densification process. Thepresented experiment used microwave radiation for the
plasticization of beech samples.Microwave treatment causes a significant rise in wood
temperature. The temperature changes the water contained in the wood structure to
watervapour [1]. Vapour causes physical reaction of wood components in the structure. As
a consequence of thermal expansion, the cellulose crystal grid expands and lignin in the middle
lamella and cell walls is softened [2]. The wood modified in this way can be densified using
pressure. Navi and Girardet [3] stated that wood densification leads to an improvement of its
mechanical properties.
The aim of this experiment was to evaluate the effect of microwave plasticization (MP) and
the following densification of beech samples on their final density and density profile. The
samples were divided based on anatomical directions into radial and tangential samples.
For the experiment, four samples were produced (2 radial and 2 tangential) from the wood
of European beech (Fagus sylvatica L.). One radial sample and one tangential sample with
dimensions 8×40×40 mm3 were used for densification. The other radial and tangential samples
were used as control samples. Their dimensions were 4×40×40 mm3. The samples were
produced from the radial and tangential sections of an above-ground stem part.
The MP was conducted using the continual device described in detail in our previous
work [4]. The output was set to 3.5 kW and the conveyor speed to 0.4 m min-1. Immediately
after MP, both samples were put in the press and densified to 50% of their original thickness,
i.e. to 4 mm. Subsequently, the densified and the control samples were conditioned to 12%
moisture content. Then their density profile was measured perpendicular to the densification
direction using an X-ray densitometer. The density profile was measured once for each sample.
The data measured by X-ray densitometer were evaluated statistically. Coefficients of variation
of the density (Tab. 1) were calculated as the quotient of standard deviations and mean
densities.
117
Tab. 1 shows that the microwave plasticized and densified samples have a higher density in
comparison to control samples. The mean density of radial and tangential samples increased by
372 kg m-3 and 313 kg m-3, respectively. The differenceiscaused by a differentproportionof
earlywood and latewoodin the radialand the tangentialsamples. The radial sample contained
more latewood, which is less porous than earlywood. Therefore, density of latewood increases
more than earlywood even if the pressure is the same. Coefficient of variation (COV) of the
density measurements decreased from 1.466 in the control radial sample to 0.978 in the
densified radial sample and from 5.112 in the control tangential sample to 2.098 in the
densified tangential sample (Tab.1). The greater COV decrease of the tangential samples is
caused by a higher proportion of earlywood. The decreasing COV of both types of densified
samples proves that the MP mode was well chosen. The samples were plasticized evenly in the
entire cross-section and they were also evenly densified.
Table 1: Statistical evaluation of density in densified and control samples
Density [kg . m-3]
Minimum
Maximum
Average density
Variation coefficient
Radial densified
1126
1187
1154
0.978
Radial control
746
814
782
1.466
Tangential densified
833
934
880
2.098
Tangential control
486
641
567
5.112
Sample
CONCLUSIONS
 The results show that the density of the densified samples increased compared to the
control samples.
 The density profile of densified samples is more homogeneous.
 The samples were densified evenly, i.e. they were plasticized in the entire cross-section.
REFERENCES
[1] Antti AL, Perré P (1999) A microwave applicator for on line wood drying: Temperature and
moisture content distribution in wood. Wood Sci Technol33(2):123-138. doi:
10.1007/s002260050104
[2] Kollmann F, Schmidt E, Kufner M, Fengel D, Schneider A (1969) Gefüge- und
Eigenschaftsänderungen. Holz Roh Werkst 27(11):407-425. doi:10.1007/bf02604735
[3] Navi P, Girardet F (2000) Effects of thermo-hydro-mechanical treatment on the structure and
properties of wood. Holzforschung 54(3):287-293. doi: 10.1201/b10143-10
[4] Koiš V, Dömény J, Tippner J (2014) Microwave device for continuous modification of wood.
BioResources 9(2):3025-3037. doi: 10.15376/biores.9.2.3025-3037
118
IMPROVING THE DIMENSIONAL STABILITY OF WOOD MODIFIED
BY SILICON-BASED CHEMICALS
V. Borůvka*, M. Pánek, A. Zeidler, S. Doubek
Czech Unversity of Life sciences,Faculty of Forestry and Wood Sciences
Kamycka 1176 Suchdol-Prague, Czech Republic
*
INTRODUCTION
Wood is a material with low dimensional stability when in contact with moisture or water
[1]. Higher moisture content can also increase the risk of fungi and insect damage of wooden
elements with lower natural durability [2]. There are several ways of protecting wood, e.g.
using suitable construction methods, preservatives, various ways of modification [3]. One way
to decrease moisture and water absorption and increase the durability of weathered wood is to
use silicone compounds for its modification [4, 5, 6]. Results of experiments are promising, but
the cost of some used types of silicone is relatively high and so the economic aspect of this
kind of modification is a limitation for wide usability.
In this experiment, usage of commercially avialable chemicals, sodium metasilicate
(Na2SiO3) and ester of alkylsiloxane (Lukofob EVO 50), as a cheap alternative for wood
modification, was tested. The main aim was to improve the dimensional stability of tree
species with a lower natural durability. The impact of these substance on mechanical properties
was also evaluated.
Pine (Pinus sylvestrisL.) and beech (Fagus sylvatica L.) wooden samples have been used for
this experiment. Dimensions of samples were 20x20x30 mm (TxRxL) for shrinkage tests and
20x20x300 mm (TxRxL) for the modulus of rupture (MOR) tests. Silicone compounds of
sodium metasilicatein c = 10% and of ester of alkylsiloxane in c = 10%have been used for
impregnation.Four different ways of wood samples impregnation by 24 hour of dipping have
been used:
 Dipping in sodium metasilicate
 Dipping in ester of alkylsiloxane
 Dipping in ester of alkylsiloxane in the 1st step and in sodium metasilicate in the 2nd step
 Reference samples of beech and pine wood without any treatment
Retention of solutions was measured after the dipping. After the seasoning of samples into
the equilibrium moisture content (T = 20°C, RH = 65%), testing of MOR, MOE and
volumetric shrinkage were performed.
RESULTS
Figure 1 shows the impact of the individual treatments on volumetric shrinkage. There was
a statistically significant decrease in dimensional changes for both of the species in most cases
when the modification was used.
119
Figure 1: Impact of treatment on volumetric shrinkage (A – beech, B – pine, 1 - sodium metasilicate, 2 – Lukofob, 3 sodium metasilicate and Lukofob, 4 – reference)
Figure 2 shows the impact of the individual treatments on the mechanical properties. Except
for Lukofob, a statistically significant decrease in bending strength was confirmed for both the
species tested.
Figure 2: Impact of treatment on bending strength (A – beech, B – pine, 1 - sodium metasilicate, 2 – Lukofob, 3 sodium metasilicate and Lukofob, 4 – reference)
CONCLUSIONS
Commercially available products containing silicone can be used to decrease the
dimensional changes in wood when necessary. It is important to keep in mind that such wood
should not be used for construction purposes as the mechanical strength has decreased.
REFERENCES
[1] Požgaj A, Chovanec D, Kurjatko S, Babiak M (1993) Štruktúra a vlastnosti dreva (Structure
and properites of wood). Príroda a.s. Bratislava. 486 p
[2] Reinprecht L, (2008) Ochrana dreva. (Wood Protection), Handbook, Technical University in
Zvolen, 453 p
[3] Hill CAS (2006) Wood modification – chemical, thermal and other process. John Willey &
Sons Ltd. Chichester, UK, 239 p
[4] Mai C, Militz H (2004) Modification of wood with silicone compounds. Treatment systems
based on organic silicon compounds a review. Wood Sci Technol 37:453-461
[5] Panov D, Terziev N (2009) Study on some alkoxysilanes used for hydrophobation and
protection of wood against decay. Int BiodeterBiodegr 63: 456-461
[6] Reinprecht L, Pánek M, Daňková J, Murínová T, Mec P, Plevová L (2013) Performance of
methyl-tripotassiumsilanol treated wood against swelling in water, decay fungi and moulds.
Wood Research 58(4):511-520
120
Session II
Advanced Wood – Polymer Composites
PHYSICAL, MECHANICAL, AND THERMAL PROPERTIES OF WOOD
PLASTIC NANOCOMPOSITES REINFORCED WITH MULTI WALLED
CARBON NANOTUBES
N. Ayrilmis* & A. Kaymakci
Istanbul University, Forestry Faculty, Department of Wood Mechanics and Technology
*
INTRODUCTION
One of the major disadvantages of wood-plastic composites (WPCs) is lower flexural and
tensile properties than plywood and oriented strandboard in load bearing structural
applications. Enhancing the flexural and tensile properties of WPCs can expand their
acceptance in structural applicatons [1]. Multi-walled carbon nanotubes (MCNs) produced by
chemical vapour deposition are the most common type of carbon nanotubes. Their microstructure consists in highly entangled agglomerates of individual cylindrical carbon nanotubes.
The carbon nanotubes have an excellent Young’s modulus and are thus a potential candidate as
reinforcement for WPCs.
The goal of the present study was to investigate the effect of MCN (1.5, 3, or 4.5 wt%) on
the physical, mechanical, and thermal properties of wood flour/polypropylene (WPC)
composites at different loadings of wood flour(30, 40, or 50 wt%).
MATERIALS
Poplar wood was used as lignocellulosic filler in the production of WPCs. The wood
particles having a moisture content of 20–30% based on the oven-dry weight of the wood were
processed by a rotary grinder and retained on a 60-mesh screen. The wood flour was dried in a
laboratory oven at 100 °C for 24 h to moisture content of 1% before the compounding process.
Polypropylene (PP) (density: 0.91 kg/m3, MFI/230 °C/2.16 Kg = 2.5 g/10 min) was supplied
and produced by Borealis Incorp in Austria and was used as the polymeric material. The
compatibilizing agent, maleic anhydride-grafted polypropylene (MAPP) (Optim-425, MFI/190
°C; 2,16 kg = 120 g/10 min, density: 0,91 g/cm3) was supplied by Pluss Polymers Pvt. Ltd. in
India. The internal (zinc stearate) and external (calcium stearate) lubricants were also used in
the extrusion process. 3 wt% MAPP and 1 wt% lubricant were used in the production of the
WPCs.
MCN was used as reinforcing filler. It was obtained from Grafen company in Ankara,
Turkey. Technical properties of MCN are presented in Table 1. The MCN (1.5, 3 or 4.5 wt%)
was added into WPC at different levels of wood flour content, 30, 40, or 50 wt%.
122
Table 1: Technical properties of multiple walled carbon nanotube.
Property
Shape
Diameter
Length
Purity
Surface area
Carbon nanotube
Black powder
10- 30 nm
10- 30 µm
> 90 %1
> 200 m2/g
PREPARATION AND TESTING OF INJECTION MOLDED WPC SPECIMENS
The wood flour, MCNs, lubricant, and plastic granulates with and without coupling agent
were processed in a 30 mm co-rotating twin-screw extruder with a length-to diameter (L/D)
ratio of 30:1. The specimens were injected at injection pressure between 5 and 6 MPa with
cooling time about 30 s. The specimens were conditioned at a temperature of 23°C and relative
humidity of 50% according to ASTM D 618. Water resistance, flexural and tensile properties,
izot impact strength, and thermogravitmeric (TGA) analysis of the specimens were determined
according to ISO standards. Dynamic mechanical analysis of the WPCs was also investigated.
RESULTS
The thickness swelling and water absorption of the WPCs decreased with increasing MCN
content but the decrement was not significant. For example at the 30 wt% wood flour content,
as the amount of MCN increased from 1.5 to 4.5 in the WPC, the 28 days TS values decreased
from 1.80 to 1.73%. This was found to be 1.80% in the control boards. Similar results were
observed in the WA of the specimens. This was mainly attributed to the hydrophobic character
of the MCNs because of its being devoid of functional polar groups such as hydroxyls in the
molecular and thus chemicallyinactive. The increment in the wood flour content increased the
TS and WA values, as expected.
The mechanical properties of the WPCs increased with an increasing content of the MCNs.
At the 30 wt% wood flour content, as the amount of the MCNs increased from 1.5 to 4.5, the
tensile strength and flexural strength of the WPCs increased. The strength values of the WPCs
decreased as the wood content increased from 30 to 50 wt% but the modulus values increased.
The flexural and tensile modulus of the WPCs significantly increased with increasing MCNs.
The impact bending strength values of the WPCs were not influenced by an increase in the
MCNs content. Furthermore, the MCNs also remarkably enhanced the storage modulus of the
WPCs. The thermal stability of the WPCs improved by the incorporation of the MCNs.
CONCLUSIONS
The results showed that the MCNs improved the strength, the modulus, and thermal stability
of the WPCs. According to the obtained results, it can be said that the optimum MCNs content
for the WPCs is 1.5 wt%.
REFERENCES
[1] Ayrilmis N, Dundar T, Kaymakci A, Ozdemir F, Kwon JH.Mechanical and thermal
properties of wood-plastic composites reinforced with hexagonal boron nitride. Poly
Composite 35:194-200
123
PROCESSIBILITY OF WOOD-PLASTIC COMPOSITES ON A
SINGLE-SCREW EXTRUDER
M. Riegler1,*, E. Sykacek2, R. Wimmer2
1
2
Wood K plus – Competence Centre for Wood Composites and Wood Chemistry
Konrad Lorenz Straße 24, 3430 Tulln, Austria
*
Institute of Natural Materials Technology – University of Natural Resources and Life Sciences
INTRODUCTION
For the extrusion of wood-plastic composites (WPC), counter-rotating twin-screw extruders
are almost exclusively used [1]. Although most important in the polymer industry, single-screw
extruders are uncommon in WPC production. Generally, single-screw extruders have
advantages such as low cost, relatively easy operation, good wear resistance, and broad
availability. Disadvantages are the lack of positive conveying characteristics, and a limited
mixing and homogenizing capability. For the processing of WPC, a higher susceptibility to
material inherent moisture variation is critical, since wood constitutes a hygroscopic behavior
even under ambient conditions. Twin-screw extruders compensate higher water-contents
through degasification zones. Here, excessive moisture is evaporated and removed from the
melted mass. Devolatilisation capacity of single-screw extruders is limited compared to twinscrew extruders, which is a major challenge in producing WPC. The aim of this study is to
assess and understand the feasibility of single-screw WPC extrusion.
WPC (57% wood, polypropylene (PP), surface additive, coupling agent, lubricant) was
extruded on a laboratory-type single-screw extruder, equipped with additional sensors to record
temperature, pressure and speed. To investigate the influence of raw material moisture on
processibility a general factorial design was used, with the moisture content (MC) varied
between 0 and 2.7%, and the screw speed (SS) varied between 10 and 60%. In total, 18 runs
were performed and the WPC profiles (simple rectangular shape) were mechanically (modulus
of elasticity (MOE), modulus of rupture in bending (MOR)) and physically (density, water
uptake) characterized. Multivariate partial-least-squares regression models were applied to
determine relationships between raw materials, process and product parameters. To validate the
models, a leave-one-out cross validation was used.
Figure 1: WPC solid profiles at SS 10 RPM and MC 0% (left), SS 10 RPM and MC 2.7% (middle) and SS 60 RPM and
MC 2.7% (right)
124
WPC profiles produced with the raw material at 2.7% MC resulted in open and torn edges,
especially at high SS (Figure 1, right). In opposite, profiles produced at lower material MC
were of superior quality, showing also higher mechanical strength (Figure 2). In particular,
mechanical strength properties differed approximately by factor two, when comparing
maximum values (e.g. SS 10 RPM, MC 0%: MOR was 26.9 N/mm², while at SS 60 RPM, MC
Design-Expert®
Softwarewas 11.1 N/mm²).
2.7%:
MOR
Biegefestigkeit
Design points above predicted value
Design points below predicted value
27.53
B ie g e fe s tig k e it
X1 = A: Feuchte
X2 = B: Drehzahl
30
modulus of rupture [N/mm²]
11.051
23
15
8
0
10
23
0.0
0.7
35
Drehzahl
screwB:speed
[RPM]
1.4
47
2.0
60 2.7
moisture
content [%]
A: Feuchte
Figure 2: 3D surface plot of influences of raw material moisture content and screw speed on MOR
Based on the multivariate regression models, mechanical properties of the extrusion profiles,
i.e. MOE (R²cv = 88.1) and MOR (R²cv = 90.6), could have been further improved by lowering
the temperatures at cylinder zone 2 and at the outlet of the extruder, respectively. Additionally,
the usage of a water-cooled gauge at the outlet of the extruder and lower SS increased
mechanical properties as well.
In summary, extruded WPC profiles on a single-screw extruder worked best when the raw
materials were absolutely dry. To further optimize the single-screw extrusion process using
raw material with increased MC, the melting process of the raw material can be simulated
using e.g. finite element modelling (FEM). Further, actual extrusion parameters should be
based on statistically-significant process parameters that are derived from the multivariate
regression models. The combination of FEM and multivariate statistical modelling is a subject
of future research.
CONCLUSIONS
 Producibility of PP-based WPC on single-screw extruder was proven to be feasible.
 Mechanical properties of WPC profiles with raw materials at a moisture content of 2.7%
could be improved by lowering the screw speed, the cylinder zone 2 temperature, and the
extruder outlet temperature. Another measure is water-cooled gauges at the outlet.
 The combination of FEM (melting process simulation) and multivariate regression
modeling is suggested for the optimization of the single-screw WPC extrusion process.
REFERENCE
[1] Wolcott MP, Englund KA (1999) Technology Review of Wood-Plastic Composites. In: 33rd
International Particleboard/Composite Materials Symposium. 103-111
125
A NOVEL WOOD COMPOSITE MATERIAL
S. Frybort1,*, T. Krenke1, U. Müller2, R. Mauritz3
1
Kompetenzzentrum Holz GmbH
Altenberger Strasse 69, 4040 Linz, Austria
*
2
Institute of Wood Technology and Renewable Materials, Boku Vienna
3
DOKA GmbH
Josef Umdasch Platz 1, 3300 Amstetten, Austria
INTRODUCTION
Different disintegration technologies, like chipping and flaking, are used for particle
production (strands, chips, flakes). All these technologies produce particles regardless of
the naturally optimized structure of wood. As a result, fibers within the particles show a
more or less random orientation resulting in a loss of strength. Additionally, str uctures
relevant for strength of wood are partially destroyed. Both lead to an insufficient utilization
of the strength properties of wood. To overcome these problems Doka started with the
development of a novel disintegration technology for producing high strength particles, so
called macro-fibres (MF), out of wood thinnings, in collaboration with Wood K plus in
2004. Instead of cutting particles this technology squeezes particles out of the log,
preserving the naturally grown fiber orientation within the particles. Hence, MF differ from
other particles by a very high slenderness ratio (>20) and high tensile strength (~
50 MPa)[1].
After a first upscaling of the MF-production technology to a semi-automatic laboratory
process in 2009, the technology was raised to a pilot plant level in 2012 (Fig. 1) [2, 3]. At
this stage the process allows sufficient supply of high quality MF for further investigations
of industrial panel production.
Using conventional adhesives (UF, MUF, pMDI) results in bending strength of around
50 MPa and E-Module of 8 GPa. To enable a reduced density of about 450 kg/m³ and
simultaneously maintain bending strength and stiffness, foamed adhesive was introduced
and further developed. Compared to OSB, the thickness swelling (~10%) of MF boa rds is
thereby reduced to around 4%.
126
Figure 1: Time history of the MF production process
CONCLUSIONS
By adapting existent technologies for panel production to the requirements of MF this novel
engineered wood product convinces by high strength, stiffness as well as low thickness
swelling and low density.
REFERENCES
[1] Joščák T (2006) Langpartikel Holzwerkstoff aus Durchforstungsholz, in Department für
Materialwissenschaften und Prozesstechnik, Universität für Bodenkultur Wien
[2] Frybort S, Graeter P, Mauritz R, Mueller U (2012) Device for the production of macro-fibres
from wood trunks and method for the production of a wood composite material by means of
macro-fibres(WO002012042028A1)
[3] Frybort S, Graeter P, Mauritz R, Mueller U (2012) Wood composite material
(WO002012042027A1)
127
SELECTED CHARACTERISTICS OF LIGNIN-PHENOLFORMALDEHYDE RESOLE ADHESIVES
M. Ghorbani1,*, F. Liebner2, E. Van Herwijnen3, L. Pfungen1, M. Krahofer1, J. Konnerth1
1
2
BOKU- University of Natural Resources and Life Science, Institute of Wood Technology and
Renewable Materials, Konrad Lorenz-Strasse 24, 3430 Tulln an der Donau, Austria
*
e-mial: [email protected], [email protected],
[email protected]
BOKU- University of Natural Resources and Life Science, Department of Chemistry, Division of
Chemistry of Renewable Resources
Konrad Lorenz-Strasse 24, 3430 Tulln an der Donau, Austria
3
Kompetenzzentrum Holz, GmbH
Altenberger Straße 69, 4040 Linz, Austria
ABSTRACT
Phenol-formaldehyde (PF) adhesives are predominately used as wood adhesives for a
variety of applications [1]. Lignin, which is an abundant natural polymer and principal
constituent of wood, is a well-known potential substitute for Phenol in PF adhesives because of
its richness in phenolic moieties [2].
The present investigation analyses the influence of different degrees of lignin substitution
(up to 40%) with respect to the synthesis of PF adhesive and the adhesive bond performance.
Furthermore, various lignin sources were investigated, namely Sarkanda grass soda lignin, pine
kraft lignin (Indulin), beech organocell lignin (Organosolv), wheat straw soda lignin.
Lignin based phenol formaldehyde (LPF) adhesives containing the different types of lignin
at different substitution levels were prepared, optimizing the adhesive synthesis towardsa
degree of 20 and 40% phenol substitution by lignin. Increasing the amount of lignin, a
significant increase in polymerization rate was observed for all tested lignin types.LPF
adhesive prepared with Indulin showed faster polymerization compared to the LPF adhesives
prepared with the same amount of the other lignins (Fig. 1).
1200
Viscosity (mPa.s)
1000
800
600
400
200
PF
LPF (Sarkanda 20%)
LPF (Indulin 20%)
0
50
100
150
200
250
300
Time (min)
Figure 1: Polymerization rate during the adhesive synthesis
128
To evaluate the bonding performance of the adhesives, the Automated Bonding Evaluation
System (ABES) technique was applied. The results obtained demonstrated that the bonding
performance of LPF adhesives synthesized with Indulin performed better than LPF adhesives
synthesized with the other lignins. Also the bond strength of the adhesives with 20% lignin
substitute performed better than the adhesives with 40% lignin substitute and almost similar to
PF adhesive (Fig. 2).
Tensile shear strength (N/mm²)
8
7
6
5
4
PF
LPF (Sarkanda 20%)
LPF (Indulin 20%)
3
2
0
200
400
600
800
Time (sec)
Figure 2: Tensile shear strength development PF and LPF adhesives based on ABES technique
Shear strength test according to the European standard EN 302-1 was carried out for the
adhesives andthe results were compared with the requirements described in the standard. The
test specimens were exposed to treatment A1 (stored and tested in standard climate) and A2
(submersed in water for 24h, tested in wet conditions). The shear strength values obtained for
both PF and LPF adhesives passed the standardrequirements of A1 and for LPF adhesives even
of the A2 treatment.
In order to evaluate the curing characteristics of the various adhesives, additionally
differential scanning calorimetry (DSC) was employed. According to the DSC curves the
crosslinking peak for LPF adhesives shifted towards higher temperatures with increasing lignin
content.
CONCLUSIONS
Partial substitution of phenol by lignin accelerates the polymerization rate of respective PF
adhesives during the cooking process. Among the tested lignins, the pine kraft lignin - Indulin was the most promising substitute. With an increasing degree of lignin substitution, curing
characteristics decreased, whereas bond performance was retained up to 40% lignin content.
REFERENCES
[1] Malutan T, Nicu R, Popa I. V (2008) Contribution to the study of hydroxymetylation reaction
of alkali lignin. Bioresources 3(1):13-20
[2] Akhtar T, Lutfullah G (2011) Lignosulfonate-phenolformaldehyde adhesive: a potential binder
for wood panel industries. J Chem Soc Pak 33(4)
129
MICROSCOPIC SWELLING OF COMPONENTS IN WOOD BASED
PANELS: FIRST TRIALS
P. Klímek1,*, P. Meinlschmidt2, R. Wimmer3
1
*
2
3
Fraunhofer-Institut für Holzforschung - Wilhelm-Klauditz-Institut (WKI)
Bienroder Weg 54E, 38108 Braunschweig, Germany
Institute for Natural Materials Technology, University of Natural Resources and Life Sciences
Konrad Lorenz Strasse 20, 3430 Tulln, Austria
INTRODUCTION
In the branch of renewable materials, wood composites became very popular, for their
versatility in applications, high stiffness to density ratio and no less important sustainability [1].
These properties generally come from composites sub-components. Composite materials such
as particleboard or fiberboard basically consist of larger and/or smaller wood components
bonded by various binders, where various techniques are processed in order to achieve
homogenous material with consistent mechanical performance. Nevertheless, the mechanical
performance changes in various environments. One of the most common is a change in wood
composites thickness and shape stability as a reaction to increased moisture [3]. Although the
classical thickness swelling (EN317) may give sufficient information about product quality, the
microscopic swelling of components giving insight into the swelling behavior of composites
components is missing. In our research the following research questions are asked: (1) Is it
possible to develop a reliable method for specification of microscopic swelling in particleboard
and fiberboard? (2) Is it possible to indicate swelling behavior of various particles contained in
particleboard? (3) How is the swelling of wood fibers different to swelling of wood particles?
MATERIALS AND METHOD
By digital image correlation (DIC) the area of interest (AOI) consisting of components with
different thickness and orientations was localized in the surface layer of particleboard (PB) and
fiberboard (MDF). 2 mm of surface layer was obtained and surface was carefully sliced by
razor blade. Final samples are presented in figure 1.
To create controlled environment where swelling of samples may be captured, the climate
chamber Vötsch VLC 4006 was used. Then camera Dino lite was mounted in the stand
vertically to capture the area underneath. The 2D DIC was used to capture images of the
sample using camera Dino lite which was focused on 4.5 × 4.5 mm² Field of view (FOV). The
images were captured with resolution 1280×1024. The DIC itself was produced using software
Davis 8.1.3 software and strain in thickness (εxx) direction was calculated. The calibration of
optical measurements was performed prior to test using 1 mm grid paper. One image of the
paper was captured and the size of the image was calculated and it was 3.9 µm/pixels. Then
five images were taken and the mean value of displacement in x and y direction was calculated
and identified as error of measurement (verr). vxerr= 0.09 µm and vyerr = 0.04 µm.
130
The images for microscopic swelling identification were taken in conditions of 80 %
relative humidity and 24 °C. Images were captured for 240 minutes. The acquisition interval of
image capture was 15 minutes. Swelling profiles of PB and MDF were produced in time
intervals of 60; 120; 180 and 240 minutes.
Figure 1: Samples and setup used for DIC; A-camera, B – rigid plate, C-weight, D-AOI
The thickness swelling of particleboard was calculated to 2.5 %. The microscopic
swelling profile presented complex swelling interactions where the highest swelling was
presented by the particle placed in position 100–760 µm. The swelling was the highest due to
the swelling of wood in the tangential direction and the median value 8 % corresponding with
the swelling of pine wood in the tangential direction [19]. It seems that the voids in the central
region of the inspected area were filled by swelling of wood since swelling profile indicated
negative εxx (Figure 4-2). The last particle (figures 2–3) showing swelling from 3 to 5 %
corresponds with its radial orientation perpendicularly to the thickness.
Figure 2: The strain map (µm/ µm) of the particleboard and particle-bundle (magnification 200 ×) in the central subinspection line and microscopic swelling profile
FIBERBOARD
In MDF the strain maps (figure 5) exhibit a relatively uniform field of the strain, the MDF
was found to have more regular displacement which reached similar values as in particleboard.
The swelling was calculated to 2.4 %. Although the strain was uniformly distributed, the size
of the fibers may play an important role as well. The larger fibers localized between 400 and
650 µm of the sample (figure 3B) thickness show swelling peaks in microscopic swelling
profile. The fibers seem to swell and fill the voids in the board since higher presence of
negative εxx is indicated. More conclusions may be found when density alteration of
fiberboard with oriented fiber is included in future research.
Figure 3: The strain map (µm/ µm) of the fiberboard and larger fibers (magnification 200 ×) and microscopic swelling
profile of MDF
131
CONCLUSIONS
In our research, we successfully established the method for DIC evaluation of microscopic
changes in wood based composites which can be directly transferred and used for evaluation of
other materials. This method may contribute to the assessment of damage caused by increased
humidity; this technique may be interesting for historically valuable pieces since only a small
piece (2×2 mm²) is needed for evaluation. Secondly, in the field of wood based composites this
technique can be used for the evaluation of components swelling. Further research including
the effect of particles size, geometrical orientation or used resin should follow. The thorough
swelling profiles may explain benefits of different densities and resin distributions in wood
based panels.
ACKNOWLEDGMENT
Authors
gratefully
acknowledge
Deutsche
Bundesstiftung
Umwelt
Austauschstipendienprogramm 2014 to support project: „Green composite for sustainable
future“. The authors gratefully acknowledge the support of WKI Fraunhofer-Institute for Wood
Research (WKI) in Braunschweig and its staff for providing necessary equipment and
consultations which significantly contributed to the research.
REFERENCES
[1] Mantia FP La, Morreale M (2011) Green composites : A brief review. Compos Part A 42:579–
588
[2] Heon J, Ayrilmis N, Hyung T (2013) Enhancement of flexural properties and dimensional
stability of rice husk particleboard using wood strands in face layers. Compos Part B 44:728–
732
[3] Forest Product Laboratory. Wood Handbook: Wood as an Engineering Material. Madison,
Wisconsin: United States Department of Agriculture; 1999
132
LIGHT-MICROSCOPIC DETECTION OF NANOCELLULOSEREINFORCED ADHESIVE IN PARTICLEBOARDS
E. Mahrdt1,*, S. Pinkl1, C. Schmidberger2, H. W. G. van Herwijnen1, W. Gindl-Altmutter2
1
2
Wood K plus, Competence Centre for Wood Composites and Wood Chemistry
Altenberger Str. 69, A-4040 Linz, Austria
*
e-mail: [email protected]; [email protected]
BOKU – University of Natural Resources and Applied Life Science, Institute of Wood Technology and
Renewable Materials, Tulln, Austria
INTRODUCTION
Urea-formaldehyde resins (UF) offer many advantages for industrial applications [1],
however their mechanical performance is limited.
Because of this and mainly to reduce the brittleness of UF, several attempts have been made
to strengthen the adhesive from chemical modification of the UF to reinforcement with fibrous
materials. As UF resins have a strong adhesion to most cellulose-containing materials,
cellulose fibers seem to be best suited for strengthening UF resins [2].
As the mechanical properties of particleboards depend on the bonding quality between
wood particles, the adhesive itself and its chemical and physical properties and behaviour
within the wood adhesive interphase are of great interest. In this context, the knowledge on the
whereabouts of resin within produced boards is of great importance. Adhesive distribution is
one major aspect for the final quality of particleboards [3, 4].
Up to now it has been confirmed that the addition of fibrous fillers to UF-adhesive
reinforced the mechanical strength of produced boards [2] but it is still unknown how cellulose
nanofibers (CNFs) improve the board properties. Therefore, the aimsof the present work were
to investigate the adhesive distribution in particleboards prepared with CNF adhesive and to
verify the work hypothesis that CNF filled adhesives result in a different distribution in
produced boards than in reference boards.
One layer particleboards were produced out of industrial core layer particles. The particles
were coated in a ploughshare mixer by adding adhesive and nanocellulose (Daicel, Japan),
subsequently. The glued particles were then formed and pressed to boards. The density and
internal bond were determined according to European Standards EN 323 and EN 319.
The boards were investigated by the method of Mahrdt et al. [5]: Thin cross sections of the
investigated boards were stained with two different dyes to obtain a sufficient contrast between
the adhesive and wood. Brilliant Sulphaflavine, a fluorescent dye, was used to colour the
adhesive. Gentian Violet was used to colour the wooden components. With a fluorescence
microscope, Zeiss Axioplan 2 Imaging images were taken under both halogen- and fluorescent
light.
133
RESULTS
Aside from an identical penetration rate for both adhesive systems, the modified one shows
a significantly higher amount of adhesive in the glueline. It seems that the nanocellulose acts as
a coupling agent and contributes with its huge specific surface to an enlargement of the
adhesive area. Those larger areas might lead to a broader interface between adhesive and wood
than in the unmodified UF as well as to reinforcement of the bonding quality. Based on this
approach, the adhesive distribution within the boards corresponds well with the mechanical
board properties.
CONCLUSIONS
The mechanical performance of the particleboards could be significantly enhanced by
adding CNF to the adhesive. The method of resin detection has successfully shown how
modified resin is distributed in the boards and leads to a higher share ofthe adhesive in the
glueline.
REFERENCES
[1] Dunky M, Niemz P (2002) Holzwerkstoffe und Leime. Springer, Berlin
[2] Veigel S, Rathke J, Weigel M, Gindl-Altmutter W (2012) Particle board and oriented strand
board prepared with nanocellulose-reinforced adhesive. Journal of Nanomaterials, vol. 2012,
Article ID 158503, 8 pages, 2012. doi:10.1155/2012/158503
[3] Xing C, Riedl B, Cloutier A, Deng J, Zhang SY (2006) UF resin efficiency of MDF as affected
by resin content loss, coverage level and pre-cure. Holz Roh Werkst 64(3):221-226
[4] Riegler M, Gindl-Altmutter W, Hauptmann M, Müller U (2012) Detection of UF resin on wood
particles and in particleboards: potential of selected methods for practice-oriented offline
detection.Eur J Wood Prod 70:829–837. Doi: 10.1007/s00107-012-0628-5
[5] Mahrdt E, Stöckel F, van Herwijnen HWG, Müller U, Kantner W, Moser J, Gindl-Altmutter W
(2015) Light-microscopic detection of UF-adhesive in industrial particle board
134
Session II
Advanced Wood – Polymer Composites
Poster Session
EFFECT OF NANO-CLAY ON SOME PHYSICAL AND MECHANICAL
PROPERTIES OF WOOD POLYMER NANOCOMPOSITES
A. Kaymakci* & N. Ayrilmis
*
INTRODUCTION
Nanocomposites are materials created by introducing nanoparticulates (fillers) into a
macroscopic sample material (matrix). After adding the nanoparticulates to the matrix material,
the resulting nanocomposites may exhibit drastically enhanced properties [1]. Polymer/nano
clay nanocomposites have recently attracted a great interest because of their significant
contribution to the physical and mechanical properties of polymer composites as compared
with conventional polymer composites.
The objective of this study was to determine the effect of nanoclay on some mechanical
properties of wood polymer nanocomposites.
Polypropylene (Borealis Incorp ), nanoclay (Grafen company), and coupling agent (Optim425, MFI/190 °C; 2,16 kg = 120 g/10 min, density: 0,91 g/cm3) were used in the experiments.
Pine wood flour (40 mesh) as lignocellulosic filler was obtained from a commercial WPC
manufacturer (semawood) in Tekirdag, Turkey. The internal (zinc stearate) and external
(calcium stearate) lubricants were also used in the extrusion process. 3 wt% MAPP and 1 wt%
lubricant were used in the production of the WPCs. Experimental design of the study is
presented in Table 1.
Table 1: Experimental design of the study
WPC
Groups
Polypropylene
(wt%)
A
B
C
D
E
F
G
H
50
50
50
50
50
50
50
50
Pine Wood
Flour
(wt%)
50
50
50
50
50
50
50
50
Nanoclay
(wt%)
0
0
1,5
3
4,5
1,5
3
4,5
Coupling Agent
(MAPP)
(wt%)
0
3
0
0
0
3
3
3
Zinc
Stearate
(wt%)
1
1
1
1
1
1
1
1
Calcium
Stearate
(wt%)
1
1
1
1
1
1
1
1
Preparation and testing of injection molded WPC specimens
Depending on the composite groups, granulated polymer, wood flour, and coupling agent
were mixed. Then this homogenous mixture was compounded in a laboratory scale twin-screw
extruder at 40 rpm screw speed. Extruder temperatures were set as 170, 180, 185, 190 and
200 °C for 5 heating zones. The extrudates were collected, cooled and granulated into pellets.
Finally, pellets were injected at injection pressure between 5 and 6 MPa with cooling time
136
about 30 s. The specimens were conditioned at a temperature of 23 °C and relative humidity of
50%. Water resistance, flexural and tensile properties, izot impact strength, of the specimens
were determined according to ISO standards.
RESULTS
Some physical and mechanical properties of polymer nanocomposites with different
nanoclay contents are presented in Table 2. The incorporation of the nanoclay into the
composite improved all the mechanical properties. The impact strength of the composites was
very slightly increased by the addition of nanoclay. The MAPP improved the mechanical
properties of the composites.
Table 2: Some physical and mechanical properties of polymer nanocomposites
Composite
Groups1
Density
(g/cm3)
A
B
C
D
E
F
G
H
1.018(0.01)
1.025(0.02)
1.027(0.01)
1.028(0.01)
1.032(0.01)
1.032(0.01)
1.042(0.01)
1.042(0.01)
Tensile
Strength
(N/mm2)
15.47(0.36)
15.77(0.34)
13.82(0.55)
14.19(1.21)
15.61(0.91)
15.67(0.32)
16.03(1.93)
16.50(0.93)
Tensile
Modulus
(N/mm2)
4038(256)
4326(598)
4179(167)
4209(551)
4231(262)
4356(306)
4380(382)
4392(411)
Modulus of
rupture
(N/mm2)
34.86(2.91)
36.01(0.88)
33.79(0.66)
34.42(0.52)
35.47(0.78)
35.83(0.60)
37.06(0.80)
38.33(1.10)
Modulus of
elasticity
(N/mm2)
4668(721)
4885(391)
4725(626)
4888(887)
5041(518)
5365(824)
5735(664)
5764(615)
Izod impact
strength
(kJ/m2)
1.30(0.03)
1.34(0.02)
1.33(0.03)
1.36(0.03)
1.39(0.03)
1.41(0.03)
1.45(0.07)
1.47(0.05)
1
See Table 1 for the composite formulation.
CONCLUSIONS
The results showed that the nanoclay improved some physical and mechanical properties of
the nanocomposites. Based on the findings obtained from the present study, it can be said that
the optimum amount of nanoclay for the WPC is 1.5 wt%.
REFERENCES
[1] Altuntas, E (2005) Polymeric Nanocomposites From Renewable Resources, M.Sc. Thesis,
Bogazici University, Chemistry, Institute for Graduate Studies in Science and Engineering,
İstanbul
137
EFFECT OF CORE LAYER COMPOSITION ON WATER RESISTANCE
AND MECHANICAL PROPERTIES OF HYBRID PARTICLEBOARD
J.H. Kwon1,*, N. Ayrilmis2, T.H. Han1
1
National University,
200-701, Chuncheon, Republic of Korea
*
2
INTRODUCTION
Urea-formaldehyde (UF) adhesive is commonly used in the manufacture of wood-based
panels. However, the UF adhesive has drawbacks of low water resistance and high
formaldehyde emission. Low density polyethylene (LDPE) remains a popular plastic in use
today because of its versatility and low melting temperature. LDPE is a suitable thermoplastic
for improving the core layer of the particleboard due to its low melting temperature which is
around 100°C. Due to its unique properties, LDPE could play an important role in the
production of particleboard having a rice husk core.
The core layer of the particleboard significantly affects the water resistance of the board due
to its high shell ratio. The improvement in the bonding between the core layer particles can
improve the water resistance and mechanical properties of the particleboard. In this study, we
focused on the effect of raw material formulation used in the core on the properties of hybrid
particleboard. For this aim, different proportions of rice husk/wood particles, and different
amounts of UF adhesive, LDPE, and maleic anhydride-grafted polyethlyene (MAPE) used in
the core layer were investigated.
The face and core layer particles were supplied from a commercial particleboard plant in
South Korea. The rice husk particles were supplied from a commercial rice mill in South
Korea. The LDPE powder (average particle size: 50 mesh, MFI: 24 g/10 min and 0.926
g/cm3,) was obtained from M.J Powder company in South Korea. The compatibilizing agent
(MAPE) (MFI/190°C, 2.16 kg = 1.5 g/10min and density: 0.93 g/cm3) powder was obtained
from Lotte Chemical Company in South Korea.
The experimental particleboards were produced under laboratory conditions. Top and
bottom surfaces were made from the fine wood particles while the core layer was made from a
mixture of wood and rice husk particles. The particles were formed into a 29 cm x 29 cm x 1
cm randomly oriented mat and pressed at 2.8 MPa for 7 minutes between platens heated to 170
°C to produce a 10 mm thick particleboard. The properties of particleboards were determined
according to European standards. Four series of particleboard core layer were produced
(Table 1).
138
Table1: Experimental design.
Phase
Phase I
Phase II
Phase III
Phase IV
Particle
board type
UF adhesive
content
(% weight)
Particle content
(% weight)
Surface
layer
Core layer
LDPE
content
(% weight)
MAPE
content
(% weight)
Surface
layer
Core
layer
Core layer
Core layer
12
8
-
-
1
Wood
30
Rice husk
70
Wood
0
2
30
45
25
12
8
-
-
3
30
35
35
12
8
-
-
4
30
25
45
12
8
-
-
5
30
0
70
12
8
-
-
6
7
8
9
10
11
30
30
30
30
30
30
35
35
35
35
35
35
35
35
35
35
35
35
12
12
12
12
12
12
8
8
8
8
8
8
5
10
15
20
25
30
-
12
13
14
15
30
30
30
30
35
35
35
35
35
35
35
35
12
12
12
12
7
5
3
1
15
15
15
15
-
16
30
35
35
12
-
15
-
17
18
19
30
30
30
35
35
35
35
35
35
12
12
12
-
30
30
30
0
1.5
3
20
30
35
35
12
-
30
4.5
21
30
35
35
12
-
30
6
RESULTS
The water resistance and mechanical properties of the particleboards having a core with a
mixture of the wood and rice husk (phase I) decreased with increasing the rice husk particle
content in the core layer. This was mainly due to the fact the wax and silica layer encirculating
the rice husk particle inhibited sufficient direct contact between the adhesive and the rice husk
particles.The thickness swelling (TS) and water absorption (WA) values of the particleboards
having a core layer produced with a mixture of 1 wt% the UF adhesive and 15 wt% the LDPE
were lower than those of the control boards produced with 8 wt% the UF adhesive. As the
LDPE is a good barrier to water due to its hydrophobic character, by replacing the UF by the
LDPE, the TS and WA significantly reduced. The water resistance and internal bond (IB)
strength of the particleboard were greatly improved by the incorporation of the LDPE powder
at the same content of the UF adhesive. The incorporation of the MAPE compatibilizer into the
polymer matrix considerably improved the water resistance and IB strength of the
particleboards.
CONCLUSIONS
Based on the findings obtained from the present study, it can be said that the water
resistance and mechanical properties of particleboards having a rice husk core can be
considerably improved by the incorporation of the LDPE powder and MAPE.
139
MECHANICAL PERFORMANCE OF LAMINATED VENEER LUMBER
BONDED WITH UREA-FORMALDEHYDE CONTAINING
MICROFIBRILLATED CELLULOSE
N. Ayrilmis1,*, J.H. Kwon2, S.-H. Lee2, T.H. Han2
1
Department of Wood Mechanics and Technology, Forestry Faculty, Istanbul University, Bahcekoy, Sariyer,
34473, Istanbul, Turkey
*
2
National University, 200-701, Chuncheon city, Republic of Korea
e-mial: [email protected], [email protected], [email protected]
INTRODUCTION
Deformation of urea-formaldehyde (UF) adhesive layer under mechanical loading is
usually small because the cured UF adhesive’s elastic modulus is high. As a result, stress
concentrations along the bond line of a wood adhesive joint are generated that reduce the
overall strength of the joint. In this study, mechanical properties of laminated veneer lumbers
(LVL) produced with the UF adhesive having different amounts of microfibrillated celluloses
(MFCs) were investigated. Gel time, viscosity, and acidity of the E0 and E1 class UF adhesives
with the MFCs were determined.
Materials
Two different formaldehyde classes (E0 and E1) of commercial liquid UF adhesive were
used in the production of LVLs. The solid contents of E0 and E1 class adhesives were 63.3 and
60.5%, respectively. The wood powder (40 mesh, pinus densiflora) suspensions were prepared
by adding distilled water and then the concentration of suspension was adjusted to 1 wt%. The
suspension was then passed through the wet disk mill (Supermasscolloider MKCA6-2, Japan).
The rotational speed of disks was set up at 1.800 rpm. The reduced clearance between
rotational disks was 150 µm from fiducial zero point. Operation cycles were repeated from 1
pass to 15 passes.
Preparation of UF adhesives modified with MFCs
The E0 and E1 class UF adhesives were modified with different amounts of the 5 wt%
MFCs suspension (Table 1). The UF adhesive containing the MFCs suspension was mixed
with magnetic stirrer (1000 rpm) for 3 h at room temperature to achieve a proper distribution of
MFCs in the UF adhesive. 1 wt% of ammonium chloride based on solids content of the UF
adhesive was added to the adhesive mixture. The hardener was added into the adhesive mixture
during the last 5 min.
Figure 1: Production of MFCs and dispersion in the UF adhesive using stirrer.
140
Manufacturing and testing of LVL panels
After preparing veneers (Pinus densiflora) with dimensions of 250 mm × 250 mm × 3.6 mm,
3-layer LVL panels were produced. The experimental design is presented in Table 1. The hotpress pressure, temperature, and time for the LVL mats were 1.5 N/mm2, 150 °C, and 13 min,
respectively. Two LVL panels (10 mm thick) were produced for each type of adhesive
formulation. Three-point bending strength (MOR) and modulus of elasticity (MOE) in bending
were determined in accordance with EN 310 (1993). Tensile-shear strength (TSR parallel
direction to the grain of the surface layers of LVLs was determined according to EN 314-1
(2004). The viscosity (Brookfield DV-II+) and gel time (Sunshine gel-time meter), and acidity
of the different mixtures of the UF adhesive and the MFC were determined. The structure and
appearance of the MFCs in the UF adhesive were investigated using Scanning electron
microscopy (SEM). The densities of LVL panels ranged from 0.56 to 0.59 g/cm3.
RESULTS
The MOR, MOE, and tensile shear strength of the LVLs improved with the incorporation of
MFCs (Table 1). At the same content of the MFCs, the bonding performance of the E0 class
UF adhesive improved more than that of the E1 class UF adhesive. The tensile shear strength
of the LVLs improved with increasing suspension of the MFCs content up to 3.75 g in the 7.50
g liquid E0 class UF adhesive while this was found to be 2.5 g for the E1 class UF adhesive
(8.75 g). The higher bond strength for the UF adhesive containing the MFCs could be
explained by the possible reaction between the methylol groups of the UF adhesive and the
hydroxyl groups of the cellulose. Substantial increases in the viscosities of the UF adhesives
were observed as the amount of MFCs increased in the adhesive. The gel time of the UF
adhesives increased with increasing amount of the MFCs.
Table 1: The mechanical properties of the LVLs.
Quantity
MOR
MOE
Tensile
(resin applied on a single surface of veneer (25 × 25 cm))
(N/mm2)
(N/mm2)
shear
strength
Liquid
MFCs suspension
Hardener
(N/mm2)
UF resin (g)
5 wt%) (g)
(g)
A
11.25
0.00
1.13
56.5
7500
2.89
B
10.00
1.25
1.00
59.7
7570
3.07
C
8.75
2.50
0.88
75.4
8356
3.14
D
7.50
3.75
0.75
64.8
7835
3.35
E
6.25
5.00
0.63
53.5
6277
3.26
F
11.25
0.00
1.13
67.8
7706
3.10
G
10.00
1.25
1.00
76.7
8902
3.01
H
8.75
2.50
0.88
69.6
7205
3.16
I
7.50
3.75
0.75
58.1
7727
2.94
J
6.25
5.00
0.63
60.6
6896
3.11
*The quantity of each type of adhesive mixture was calculated based on the 180g/m2 of adhesive spreading.
class
E1
UF
(60.5 wt%)
class
E0
UF
(63.3 wt%)
LVL type
CONCLUSIONS
The results of the study showed the flexural properties and bond strength of the LVLs could
be improved by the incorporation of the MFC suspension in the E0 and E1 class UF adhesives.
REFERENCES
[1] Veigel S, Muller U, Keckes J, Obersriebnig M, Gindl-Altmutter W (2009) Cellulose nanofibrils
as filler for adhesives: effect on specific fracture energy of solid wood-adhesive bonds.
Cellulose 18:1227-1237
141
OPTIMIZATION PROCESS OF NATURAL-FIBRE NONWOVENS
Š. Hýsek1,*, M. Böhm1, R. Wimmer2
1
Faculty of Forestry and Wood Sciences, Czech University of Life Sciences Prague,
Kamýcká 1176, 165 21 Prague 6 - Suchdol
*
2
Institute of Natural Materials Technology, University of Natural Resources and
Life Sciences,Vienna, IFA Tulln, Vienna, Konrad-Lorenz-Straße 20, 3430 Tulln an der Donau
INTRODUCTION
Renewable natural fibre materials are in conformity with the goal of reducing energy
consumption and CO2 emissions. “Green” fibres can be used as an alternative to glass fibres in
many fields of applications, including automotives, due to their lower density, easy handling, good
acoustic properties, recycling capabilities and a lower price. Natural fibres from plants may be
wood, but also flax, hemp, jute, sisal, abaca, palm, cotton, coir, or kapok. The presented research
deals with the processing of air-laid nonwovens using the natural fibres of hemp and flax. The main
goal is the improvement of properties of nonwovens manufactured with a small-size air-laying
nonwoven machine.
SPIKE® air-laying technology from the Formfiber Denmark APS company was used. The
technology is based on dry forming of a fibre web in a forming box [1]. Fibre-separating rollers
(spike rollers) singularise fibres from fibre clumps. The technology can produce mats from natural
fibres as well as synthetic fibres, or recycled fibres. There are two types of machine settings that are
known to have an influence on the web quality: velocity and direction of production. Apart from
evaluating the machine settings and web properties, fibre deposition dynamics and process time of
particular machine elements were observed.
Baled hemp straw as well as flax-fibre bundles were loaded onto a mechanical carding machine
for opening and removal of shive fractions [2]. As shives primarily came from the hemp straw, this
separation process was done multiple times. There are particles from stem mainly in the hemp
bales and this material is treated in the opening-roller three times. Opened and separated fibres
were fed into the suction pipe of the air-laying machine. Feeding was done as continuous as
possible. Speed and direction of rotation of the rotating spike wheels were adjusted to various
combinations. Fibre mats with area weights of 800 kg·m-2 were produced. Mechanical-needle
punching was applied as fibre mat reinforcement [2]. The feeding speed for needle punching was
set to 0.45 m·min-1, and the punching rate was 118 strokes·min-1. The needle-head held 442
needles, with 125 x 490 mm in dimension. To evaluate the quality of the reinforced nonwoven mat,
various parameters were measured. Prior to needle-punching, the fibre orientation angle in the
formed mat was registered. Some mat properties were qualitatively determined, including surface
waviness along and across the production direction, visible low-density regions with the mat, size
and frequency of fissures. Tensile strength and stretch of the needle-punched reinforced mats along and across the production direction - were measured.According to literature [3, 4], from each
nonwoven mat five specimens were cut in the longitudinal direction, and five specimens in the
transversal direction. The initial sample was always cut at 100 mm distance from the edge of the
142
fibre mat. The specimen length was 340 mm, the width was 50 mm. A universal testing machine
was used for tensile tests at constant load rates. The distance between clamps (gauge length) was
set to 200 mm, and the extension rate was 100 mm·min-1. In the case of a broken specimen at the
edge or in the jaws, data were discarded and another specimen was taken until acceptable data were
obtained. The basis weight of the fabrics was also measured.
RESULTS
First data show that the direction of spike-rotation of certain wheels had a strong influence on
the fibre deposition alignment (trajectory). For the quality of obtained nonwovens a four-level scale
was used. It could be observed that the two fibre-separating rollers positioned at the exit side of the
mat had the most significant influence. Fig. 1 shows the two machine settings identified to deliver
the best quality fibre mats. The side view of the lower part of the forming box is shown. The two
bottom rows of spike rollers, as well as a part of the running belt-screen (dashed-line) are shown.
The dotted-line represents the connections among the spike wheels, which are running in same
direction at identical rotation speed. Arrows show directions of rotations.
Figure 1: Two settings of rotation direction of spike wheels, delivering the best fibre mats.
DISCUSSION
The observation of fibre trajectories in the forming box shows that the upper two rows of
spike rollers reduce fibre clusters and have an influence on productivity. It is supposed that the
settings of these two rows of fibre separating rollers in combination with a belt screen may be
used to adjust the productivity of the air-laying technology. The bottom two rows of spike
rollers determine the fibre trajectory in the lower part of the forming box and this phenomenon
has a great influence on web quality. The density of nonwovens can be adjusted using these
spike rollers. To make a fibre web with high density the rotation direction of the spike rollers
can be used, as shown in Fig. 1 on the right. The spike roller in the right lower corner blows
fibres against the production direction, thereby fibres are compressed.
REFERENCES
[1] Andersen C (2009) Fiber distribution device for dry forming a fibrous product and method.
Formfiber Denmark APS, assignee. Patent US 7,491,354 B2. 17 Feb.
[2] Das D, Pradhan AK, Chattopadhyay R, Singh SN (2012) "Composite Nonwovens." Textile
Progress 44.1:1-84
[3] EN 29073-3:1992. Test method for nonwovens: part 3: determination of tensile strength and
elongation. Bruxelles: European Committee for Standardization
[4] EN ISO 9073-18:2007. Textiles - test methods for nonwovens: determination of breaking
strength and elongation of nonwoven materials using the grab tensile test. Bruxelles: European
Committee for Standardization
143
Session III
Innovation Trends, Environment & Markets
INDUSTRY 4.0 – A NEW APPROACH FOR WOOD MANUFACTURING
A. Teischinger
BOKU, Vienna, Institute for Wood Technology and Renewable Materials
A-3430 Tulln, Konrad Lorenz Strasse 23, Austria
INTRODUCTION
Fig. 1 illustrates that a manufacturing system is embedded in a complex environment of
economic, legal, political, technical issues. Concerning the primary processing of wood, the
decision on the production site is strongly connected to the raw material resources due to the
economically viable transport radius of the raw material. On the other hand, various industrial
sectors have moved from Central Europe to low-wage countries for different reasons in the last
years. Low wages might have been the main driving force but also lower environmental
standards etc. may be considered as reasons for this relocation of production.
Figure 1: Various environments of a production system according to [1].
The wood industries are squeezed between the necessity of economically competitive
production costs and the access to the raw material wood. Therefore, especially secondary
wood processing and furniture productions, when the raw material allocation radius is not an
issue anymore, tend to relocate the production to low-wage countries.
With the production concept of industry 4.0 a new manufacturing system is emerging in
order to keep the industrial production in Europe. Industry 4.0 is a collective term for a
production system in a smart factory based on the technological concepts of cyber-physical
systems, the Internet of Things and the Internet of Services as shown in fig. 2.
Within the modular structure of Smart Factories of Industry 4.0, cyber-physical systems
monitor physical processes, create a virtual copy of the physical world and make decentralized
decisions. Via the Internet of Things, Cyber-physical systems communicate and cooperate with
each other and with humans in real time. According to [2], both internal and crossorganizational services are offered and utilized via the Internet of Services, by participants of
the value chain.
145
Fig. 2: Industry 4.0 and „Smart Factory“ as the core part of the Internet of Things and Services (according to [3]).
The term "Industry 4.0" was first introduced at the Hannover Fair in 2011. It originates from
a project in the high-tech strategy of the German government, which promotes the
computerization of the manufacturing industry. There are six Industry 4.0 design principles
which support companies in identifying and implementing Industry 4.0 scenarios.
 Interoperability: the ability of cyber-physical systems (i.e. workpiece carriers, assembly
stations and products), humans and Smart Factories to connect and communicate with
each other via the Internet of Things and the Internet of Services
 Virtualization: a virtual copy of the Smart Factory which is created by linking sensor data
with virtual plant models and simulation models
 Decentralization: the ability of cyber-physical systems within Smart Factories to make
decisions on their own
 Real-Time Capability: the capability to collect and analyze data and provide the derived
insights immediately
 Service Orientation: offering of services (of cyber-physical systems, humans or Smart
Factories) via the Internet of Services
 Modularity: flexible adaptation of Smart Factories to changing requirements by replacing
or expanding individual modules
Characteristics for industrial production in an Industry 4.0 environment are the strong
customization of products under the conditions of high flexibilized (mass-) production. The
required automation technology is improved by the introduction of methods of selfoptimization, self-configuration, self-diagnosis, cognition and intelligent support of workers in
their increasingly complex work.
The presentation summarizes the potential of industry 4.0 in the wood industries, especially
by linking small and medium sized companies (including crafts) and industry to a smart wood
manufacturing system as proposed by [4].
REFERENCES
[1] Günther HO, Tempelmeier H (2000) Produktion und Logistik, Springer Berlin
[2] Hermann M, Pentek T, Otto B (2015) Design principles for industry 4.0 scenarios: a literature
review. Working Paper No. 01/2015. Business Engineering Institute St. Gallen, CH 9008 St.
Gallen
[3] Kagermann H, Wahlster W, Helbig J (Hrsg.) (2013) Deutschlands Zukunft als
Produktionsstandort sichern. Umsetzungsempfehlungen für das Zukunftsprojekt Industrie 4.0.
Ab Abschlussbericht des Arbeitskreises Industrie 4.0. acatech – Deutsche Akademie der
Technikwissenschaften e.V.
[4] Gronalt M, Teischinger A (2015) Industrie 4.0 – Die Produktion in der Holzwirtschaft von
morgen? Teil 1. Holztechnologie 56(3):20-23
146
GRADING OF SPRUCE TIMBER USING LASER INDUCED
FLUORESCENCE (LIF)
N. Ruminski1,*& F. Hapla2
THÜRINGENFORST -Anstalt öffentlichen RechtsForstliches Forschungs- und Kompetenzzentrum Gotha, Jägerstraße 1, 99867 Gotha,
*
1
Georg-August-Universität Göttingen
Wood Biology and Wood Products, Büsgenweg 4, 37077 Göttingen,
2
INTRODUCTION
The grading of logs and sawn timber regarding the inner wood quality especially the
occurrence of decay is a very important and a price sensitive quality feature. The inner wood
properties of logs are rated visually on the cross cut of the log or on the lateral surface after
debarking. At present there is no measurement system available on the market that can rate the
inner wood quality by optoelectronic devices on the crosscut. Different measurement systems
are available which work with X-ray but these systems are incapable to detect features that are
not connected with changes of wood density. Beginning rot or the color change of the wood
caused by fungi is not associated with the needed changes of wood density [1]. Also the
investment costs and the security requirements are relatively high. Optoelectronic
measurements systems are not able to detect the color changes caused by decay because of the
inhomogeneity of wood color and wood features that can look like decay, e.g. reaction wood or
the wood texture. Therefore, the idea is to detect red rot by measuring the laser induced
fluorescence properties of spruce wood and the change of the induced fluorescence in the
decayed wood regions [2].
To test the capability of laser induced fluorescence spectroscopy and to detect red rot in
round wood and sawn timber, 25 round wood samples with diameter between 37 and 50 cm
and 20 sawn timber samples with radial/tangential surface 21 to 50 cm were tested. The
samples were tested green with an average moisture content of ~35% and air dried with
average moisture content of ~12% (Table 1). Measurements were done every 1 by 1 cm. The
fluorescence of the sample was excited by a laser with a wavelength of 532 nm and measured
with a fluorescence spectrometer within wavelength from 530 to 980 nm with a spectral
resolution of 0.4 nm. The measurements were done in a dark chamber and the data acquisition
was performed by a measuring script. For each measuring point a full fluorescence spectrum
was collected and the position on the wood sample was captured. For each measuring position
the wood properties were rated visually in one of the 6 categories (Table 2). The moisture
content of the wood was measured with a Hydromette HT 85 T with the surface device to show
the effect of the moisture content by comparison of green and dried samples. The data
management and analysis was performed in Matlab R2013a. Therefore, different data analysis
scripts were built and applied to the data.
147
Table 1: Samples and measurements
Sample
size
Round wood 15
Sawn timber 20
Samples
Sample
dimensions[cm]
37-50 x 10 (crosscut surface)
21 x 50 (radial/tangential surface)
Spectra measurements
green / dried (each)
~ 47000
~ 18800
Table 2: Measuring point properties (visual rating)
Sound wood
Discolored or slightly
decayed wood
Decayed wood
Branch
Not assigned
Outside
Sound round wood samples are divided into sapwood and heartwood; Sawn
timber samples are not divided into sapwood and heartwood
Discolored or slightly rotted wood, wood structure is intact
Heavily decayed wood, wood structure is not intact and the wood is soft
Branches on the wood surface
Not assigned measuring points, e.g. measuring point which is partially decayed
wood and partially sound wood
A lot of measurements were outside the samples because of the round shape of
the round wood samples
RESULTS
The fluorescence measurements show differences between the sound wood and the decayed
parts of the wood. To calculate the differences the spectra were divided into three regions, two
regions without any useful information and one region of interest with a wavelength range
from 540 nm to 790 nm. The spectra of the decayed wood parts show a shift of the
fluorescence maxima of the spectrum. When the fluorescence is excited with a laser with a
wavelength of 532 nm, the spectral maxima shift within wavelength from ~600 nm to ~604 nm
depending on the grade of decay. There is a slight correlation between the grade of decay and
the shift to longer wavelength of the spectra because heavily rotten wood has a higher shift to
~612 nm. In order to check if this relation works for all measuring points, multivariate data
analysis and different supervised and unsupervised learning processes were used. To evaluate
the difference between sound and decayed wood an algorithm was developed and applied to
the not assigned measurements. The main input variables of the algorithm are shown in figure
2. The performance of the developed algorithm was very good and all measurements were
assigned to a group. With the help of the developed algorithm it was possible to divide the
measurements into different grades of decay. There are differences in the fluorescence
measurements between the green and dried samples. The shift of the spectra exists in green and
dried samples.
Additionally, a measurement system that is able to take laser induced fluorescent pictures
was built and tested on different samples. The system was able to measure the differences
between sound wood and decayed wood independent of the moisture content of the samples.
This imaging system showed a great potential to be developable into an industrial-suited
application.
148
Figure 1: Input variables of the data analysis
CONCLUSIONS
 Laser induced fluorescence in connection to ingenious data analysis could be used to
detect decay in round wood and sawn timber.
 Differences between green and dried timber have to be appropriately taken into
consideration when an analysis algorithm is created.
 Different excitation wavelengths should be tested and could lead to different results.
 The influences of an industry environment e.g. sunlight, temperature changes, vibrations,
dust or dirt should be examined.
ACKNOWLEDGMENT
The results shown in this paper are part of a running PhD-graduation. The measurements
were performed in the spectral laboratory of the company Lasertechnik Berlin GmbH.
REFERENCES
[1] Petutschnigg AJ, Flach M, Katz H (2002) Rotfäuleerkennung bei Fichte in CT-Bildern, Holz
Roh Werkst 60:219-223. doi.10.1007/S00107-002-0287-Z
[2] Antikainen J, Hirvonen T, Kinnunen J, Hauta-Kasari M (2012) Heartwood detection for Scotch
pine by fluorescence imaging analysis. Holzforschung 66:877-881.doi 10.1515/hf-2011-0131
149
ANALYSIS OF DIFFERENT WOOD PRODUCT LINES OF SWEET
CHESTNUT (CASTANEA SATIVA MILL.)
S. Eichhorn1,*, R. Németh2, F. Hapla 1
1
Georg-August-University of Göttingen, Department Wood Biology and Wood Products
D-37077 Göttingen, Büsgenweg 4, Germany
*
e-mail: [email protected]; [email protected]
2
University of West Hungary, Institute of Wood Sciences
H-9400 Sopron, Bajcsy-Zsilinszky str. 4, Hungary
INTRODUCTION
Transportation costs underscored by climate change and its related effects as well as
changing awareness regarding our behavior towards the environment promote the use of local
wood species. Additionally, the EU timber trade regulation that entered into force in 2013 and
prohibits the import of illegally harvested timber will promote the future use of indigenous tree
species [2]. The associated search for alternatives to tropical wood with high natural durability
will increase the demand for e.g. Sweet chestnut wood significantly. Due to its durability, the
heartwood of Sweet chestnut (durability class 2 according to DIN EN 350-2 (1994) [1]) is
ideally suited for use in the hazard classes 3 and 4. It allows for a long-term outdoor use
without any chemical wood preservation. Thereby, Sweet chestnut makes an important
contribution to the environment. Current investigations on the Sweet chestnut wood quality as
well as its by-products (chestnut and honey) clarify the economic importance of this tree
species [3, 4, 5, 6]. The Sweet chestnut plays an important role especially in the forestry of
south-west Germany. Nowadays, Sweet chestnut wood is used especially in the avalanche
protection and the rehabilitation of the protection forests in the mountains as well as for
gardening and landscaping. Given its oak-similarity, Sweet chestnut wood is also used
increasingly in the veneer and furniture industries.
In the course of this investigation wood product lines were analyzed based on Sweet
chestnut roundwood assortments and prices from the Haardt and Ortenau regions [7]. The
value chains and product lines of the roundwood assortments, fuel wood, palisade wood, small
sized roundwood and large dimensioned roundwood were presented in flow charts.
Furthermore, the gross added value of Sweet chestnut wood processing companies was
calculated by the subtraction method using example scenarios [8].
RESULTS AND CONCLUSIONS
The results show that the value chains of Sweet chestnut wood assortments in addition to the
primary production and the utilization in general include two stages of added value.
Furthermore, the value chains include a small number of companies. Within one company
usually several production steps are taken and a direct marketing of the finished products is
aspired (Figure 1). The product lines can be divided into the sectors of roundwood,
intermediate products and finished products. The calculation of the operational gross added
value shows that the processing of the assortment “large dimensioned roundwood” for sliced
150
veneer or sawn timber and the final processing to high-quality furniture is the highest stage of
the added value of the Sweet chestnut wood (Figure 2).
Primary
production
1st stage of
added value
2nd stage of added value
Utilization
Interior
finishing
Sweet chestnut
wood with a
rotation period of
60 years +
middleman
Final
customer
Joinery
Veneer mill
Furnitureindus
try
middleman
Figure 1: Value chain of the Sweet chestnut wood assortment "large dimensioned roundwood". Potential
middlemen as well as direct marketing, from veneer mill to the final customer, are shown with a ruptured line.
Figure 2: Sweet chestnut stem with high value (mid-diameter 0.56 m; length 10.00 m; total volume 2.50 m³) with the
Batch-No. 531 (539 €/ m³, left); Smoked sliced veneer of Sweet chestnut (830 m²) from the section (0.9 m³) of the stem
with the Batch-No. 531 (right). The calculation of the operational gross added value of the assortment “large
dimensioned roundwood” delivered an average value of 14,450 € for the processed stem section (0.9 m³).
REFERENCES
[1] DIN EN 350-2 (1994) Dauerhaftigkeit von Holz und Holzprodukten – Natürliche
Dauerhaftigkeit von Vollholz. Teil 2: Leitfaden für die natürliche Dauerhaftigkeit und
Tränkbarkeit von ausgewählten Holzarten von besonderer Bedeutung in Europa.
[2] EUTR – Verordnung (EU) Nr. 995/2010 des Europäischen Parlamentes und des Rates vom 20.
Oktober 2010 über die Verpflichtungen von Marktteilnehmern, die Holz und Holzerzeugnisse
in Verkehr bringen. Holzhandels-Sicherungs-Gesetz (HolzSiG) vom 11. Juli 2011 (BGBl. I S.
1345), Durchführungsgesetz in Deutschland
[3] Happe R, Rust S, Hapla F (2013) Eignung von Schall- und elektrischer Widerstandstomografie
zur Detektion von Ringschäle an stehenden Edelkastanien (Castanea sativa Mill.). Teil 1:
Anwendung und Interpretation der Tomografiesysteme. Holztechnologie 53(6):39-43. Teil 2:
Kritische Analyse der Untersuchungsergebnisse. Holztechnologie 54(1):34-39
151
[4] Losemann F, Koch G, Hapla F (2015) Jahrringstrukturelle Untersuchungen der anatomischen
und chemischen Zellparameter sowie der Dichteverteilung im Holz der Edelkastanie (Castanea
sativa Mill.). Teil 1: Anwendung des Mikroskopie-, Universalmikrospektralphotometrie- und
Computertomographieverfahrens. Holztechnologie 55(5):10-17. Teil 2: Vergleichende Analyse
der Messergebnisse. Holztechnologie 56(1):5-10
[5] Militz H, Busetto D, Hapla F (2003) Investigation on natural durability and sorption properties
of Italian Chestnut (Castanea sativa Mill.) from coppice stands. Holz RohWerkst 61(2):133141
[6] Schabacker A, Eichhorn S, Hapla F (2015) Untersuchung über die wirtschaftliche Bedeutung
von Nebenerzeugnissen der Edelkastanie (Castanea sativa Mill.). Forstarchiv 86:13-21
[7] Wambsganß W, Eichhorn S, Hapla F (2013) Vermarktung der Edelkastanie (Castanea sativa
Mill.) in der Region Haardt. AFZ-DerWald 16:15-17
[8] Wenke KG (1987) Theorie der Wertschöpfung und Wertschöpfungsrechnung. Dissertation,
Universität Mainz
152
EUROPEAN PLANTED POPLAR AS SUSTAINABLE RESOURCE FOR
MULTIPURPOSE END USES
J. Van Acker1,*, N. Defoirdt1, L. De Boever2, J. Van den Bulcke1
1
Ghent University, Laboratory of Wood Technology (Woodlab)
Coupure links 653, 9000 Ghent, Belgium
*
e-mail: [email protected], [email protected]
2
The Belgian Institute for Wood Technology (CTIB-TCHN)
Hof ter Vleestdreef 3, 1070 Brussels, Belgium
INTRODUCTION
Sustainable supply of woody biomass in Europe requires new incentives towards increasing
production capacity. Planted forests and even agricultural oriented plantations of fast growing
species can provide flexible solutions. This paper briefly addresses the selection and breeding
of poplar as well as the available production systems. The major part deals with examples how
poplar wood or biomass can allow for decision making as to encourage specific energy
conversion and/or different material products. Special attention is given to the role of wood
construction and the possibility to use engineered wood products (EWP).
Based on both quantity and quality drivers and reflecting on the future socio-economic and
climate related policies some arguments pro and contra are presented. Finally, the link between
production systems and end use is discussed as depending on the time based decision making
process using sustainability as a backbone.
FOCUS ON PLANTATIONS & PLANTED FORESTS
The role of plantations has been addressed in detail by FAO (Food and Agriculture
Organization of the United Nations, www.fao.org) and they have clearly been positioned as
major drivers for future wood production [1].This has been further explored and it becomes
clear the major focus to increase production most likely is linked to planted semi-natural
forests and productive plantations as part of the type called planted forest, both positioned
centrally in thecontinuum ranging from natural forest up to trees outside forest all contributing
to wood production [2]. Poplar plantations have been important and will play a key role in
providing future wood resource. Planted poplar has become a major resource and countries like
India and primarily China have recently invested considerably [3]. In Europe poplar plantations
as a traditional cultivation system have been complemented with an interest in short rotation
coppice (SRC) intended for bio-energy production.
Mantau and co-authors [4] as well as several other studies predict that we are heading for a
worldwide deficit in wood before 2030. Poplar wood will surely be a resource of value for the
production of different products in the coming decades. Poplar wood and related wood
resources such as willow and aspen are both as forest resource and through selection and
breeding programs as plantation derived material very suitable for a wide range of application.
In a modern forestry – wood industry framework we might differentiate traditional material
uses and new energy uses. However, from a historical perspective, energy uses of wood have
always been part of our society, while material use might be more innovative than many could
imagine.
153
Poplar and willow research has been supported through the international structure of FAO
and in particular within the organization IPC (International Poplar Commission,
http://www.fao.org/forestry/ipc/en/). Since long the activities on selection and breeding have
been steered also through interactions within IUFRO (International Union of Forest Research
Organizations) with the group 2.08.04 on ‘Poplars and willows’ involved in the regular
organization of the International Poplar Symposium (IPS).
It is clear that the production of wood in natural forest will have less potential to increase
supply in relation to the expected extra demand for lignocellulosic biomass in general and
wood in particular. Hence focus should be on productive plantations and trees outside forests
(TOF). Clearly some production systems, e.g. polycyclic plantations (see LIFE+ InBioWood Increase biodiversity through wood production - LIFE12 ENV/IT/000153 http://www.inbiowood.eu/), might just be the transition between both. Several innovative ‘tree’
production systems have been introduced and even very specific genetic/breeding
improvements have been carried out to come to wood production on arable land using short
rotation like SRC (short rotation coppice). Such systems can anyhow also provide material for
wood processing and suitable for wood products like MDF (medium density fibreboard), OSB
(oriented strand board), as well as PB (particleboard) and WPC (wood plastic composites) next
to the envisaged bio-energy.
MATERIALS VERSUS BIOENERGY
Energy from biomass has become very real since we consider fossil oil derived energy less
sustainable with regard to both availability and environmental impact. Wood for energy is
taking a very important part of the woody biomass resource that is harvested in many countries,
e.g. in Africa. In relation to innovation since the start of the 21st century both green and white
biotechnologies have been particularly strongly related to newly developed poplar and willow
hybrids and their cultivation, harvesting and processing in this context. Focusing on selection
and breeding this might lead to the need for decision making related to the contradictory
aspects. On the one hand, we could promote higher lignin content related to higher energy
content and as such valuable for direct energy production based on combustion or alternative
thermochemical conversion systems like pyrolysis. But when heading for second generation
biofuels and microbiological conversion systems we might need lower lignin content or lignin
that is easier to remove likewise as for pulp and paper production. Taking into account that for
material uses the role of cellulose is critical we even need to decide from the beginning
whether to combine either options or have specific and separate strategies.
TIMBER CONSTRUCTIONS AND ENGINEERED WOOD PRODUCTS
Poplar can be classified as C18 and C24 and as such can be seen as a fair alternative
building material for softwood timber in load bearing applications. Critical parameters of the
impact of knots and knot size might also have an effect on requirements related to pruning. The
general tree and wood quality issue of the forestry – wood industry chain – is surely also valid
for poplar processing. Selection and breeding as well as specific production systems can focus
on straightness and mechanical properties alongside growth/yield traits when still aiming at
traditional higher quality wood products for material use.
Green building is using more wood and especially energy aspects are important. Timber and
engineered wood products are highly suitable to realize low energy buildings. Furthermore the
embodied energy (energy required to produce) as well as the embedded energy (energy content
that can be used at of life) are important for wood based building products. A whole new range
of EWP is readily available for timber/wood based constructions and some envisage the bright
future for tall buildings as an opportunity. A simple overview of many EWP for construction
applications are presented at websites like www.apawood.org/products. Many of these are
already based on poplar related resources like aspen.
154
Besides traditional products like plywood there are clearly options for cross-laminated
timber (CLT) as a complementary general construction material next to glulam (gluedlaminated timber) nowadays based on lumber products like machine-stress rated (MSR) lumber
(machine graded lumber). Panel products like OSB (oriented strand board) are made of aspen
or poplar strands which are bonded together under heat and pressure using a waterproof
phenolic resin adhesive or equivalent waterproof binder and considered common products in
North America. Laminated strand lumber (LSL) production in Canada resembles OSB and uses
long strands coming from fast-growing aspen or poplar. Oriented strand lumber (OSL) is made
from flaked wood strands with a high length-to-thickness ratio and the manufacture of OSL
represents the efficient utilization of wood resources because it makes use of strands from fastgrowing and underutilized species. The cross-laminated product plywood is relatively strong in
both directions when loaded on the sheathing face. When loading on the edge as a beam it is
preferable to align all veneers to the longitudinal of the beam. Laminated veneer lumber (LVL)
is structural composite lumber based on this principle and can be used as such.
Although poplar, aspen and willow are non-durable wood species, several wood protection
options can upgrade the wood and wood products considerably. Alongside traditional wood
preservation several non-biocidal treatments have been implemented by industry, in particular
in Europe. Although not a major part of the poplar wood products are involved, several treating
options like glue-line additives for plywood and chemical modifications next to thermal
modification treatments (thermally modified timber, TMT) have still a lot of potential to
enhance the performance of poplar products. This improved performance has been recorded
mainly for softwood products used outdoor or under more demanding moisture – decay prone
circumstances.
CONCLUSIONS
In an overall SWOT analysis the major strength is the fact that using the renewable resource
wood is highly compatible with the principle of sustainability. Compared to both human-made
materials and fossil fuels, advantages are evident but also lead to the need for strategic decision
making. The major weakness remains the production capacity. When the whole world would
consume similarly as Europe or North-America, we might need 2 to 3 times earth. In the
analysis, we can see the role of changing towards a bio-economy either as opportunity or as
threat. Do we need to embrace the creative destruction (revolutionizing the economic structure
from within) as this could initiate the decline for some wood products or should we focus more
on creative innovation in line with the development of (nano-)fibres, 2nd generation biofuels,
EWP’s like CLT as complementary to the current situation?
REFERENCES
[1] Carle J, Holmgren P (2008) Wood from planted forests: A global outlook 2005-2030. Forest
Prod J 58(12):6-18
[2] Jürgensen C, Kollert W, Lebedys A (2014) Assessment of industrial roundwood production
from planted forests. FAO Planted Forests and Trees Working Paper FP/48/E. Rome. Available
at: http://www.fao.org/forestry/plantedforests/67508@170537/en/
[3] FAO (2012) Improving lives with poplars and willows. Synthesis of Country Progress Reports Activities Related to Poplar and Willow Cultivation and Utilization- 2008 through 2011. 24th
Session of the International Poplar Commission, Dehradun, India, 30 Oct-2 Nov 2012. Working
Paper IPC/12. 93p. Forest Assessment, Management and Conservation Division, FAO, Rome.
Available at: http://www.fao.org/forestry/ipc2012/en/
[4] Mantau et al. (2010) EUwood - Real potential for changes in growth and use of EU forests.
Final report. Hamburg/Germany
155
FROM SECONDARY WOOD RESOURCE TO VALUE ADDED ECOPRODUCTS
L. Gurau* & M. Cionca
Transilvania University of Brasov, Faculty of Wood Engineering
B-dul Eroilor 29, 500036 Brasov, Romania
*
INTRODUCTION
One of the most ignored secondary resources, the branch wood, mainly used as firewood, is
insufficiently known and exploited in spite of limited natural resources. This could be used in
new value added products as an alternative to stem wood, providing its characteristics are
known and understood. Such initiative to increase the degree of conversion of branch wood
was a part of a national research project [2], which consisted of manufacturing branch panels
from crosscut branch prisms that can be used in small articles of decorative furniture. To use
branch wood as raw material in furniture, its physical and mechanical properties require an
investigation in relation to the microscopic and macroscopic structure. However, there is very
little data reported in the literature on the microscopic and mechanical properties of branch
wood. This paper contains a comparison between the microscopic structure, the compression
strength parallel to the grain, the bending strength MOR and modulus of elasticity MOE of
branch wood and stem wood of three species to understand the extent to which this secondary
resource, branch wood, differs from stem wood. The potential of using branch wood in new
eco-panels was also examined.
METHODOLOGY
Specimens of stem wood and branch wood of beech (Fagus sylvatica L.), maple (Acer spp)
and Scots pine (Pinus sylvestris L.) were cut for testing in compression parallel to the grain
according to [5]. Specimens of maple and Scots pine were cut to determine the modulus of
elasticity (MOE) and modulus of rupture (MOR) as in [1]. The density of each specimen was
determined before testing in accordance with [4]. The overall diameter of the raw material of
the branch wood specimens was about 60 mm for the Scots pine, 90 mm for the beech and 100120 mm for the maple.
To better understand the behaviour of branch wood and stem wood specimens subjected to
mechanical testing at a microscopic level, specimens were prepared of beech, maple and Scots
pine and examined with the SEM for high magnification details and with an optical microscope
BIOSTAR OPTECH B5 fitted with an image capture system. The latter images were further
processed with ImageJ, free software which identifies wood cells (e.g. pores) as objects, it
selects their contour and returns a mask image where only the objects (anatomical cells) of
interest are kept. Together with the mask image it provides numerical data in a spreadsheet
about the measured objects such as: area and perimeter of each object, total and average area of
objects, percentage and number of objects detected in an image. ImageJ has the advantage of
providing an objective comparison between microscopies of branch wood-stem wood with a
quantitative evaluation of the investigated parameters.
Further, small furniture objects were manufactured from branch panels of maple and Scots
pine where, for design purposes, the branch wood was crosscut. Such panels were tested in
bending according to [3].
156
RESULTS
Micrographs of transversal and longitudinal sections showed that branch wood of beech
had narrower annual rings than its stem wood and showed the highest difference from stem
wood compared to maple and Scots pine.Compared to the mature stem, the branch wood of
all species had smaller and more numerous pores, excepting maple, where the pore size was
similar. The mean area of pores lumina in branch wood of beech represented about a h alf
the mean area of those in mature stem wood, while the tracheids void area in branch wood
was app. 65% of that in stem wood of Scots pine. The pores mean frequency was about
60% greater in branch wood of beech and 17% in branch wood of maple compared to their
stem. Apotracheal parenchyma was more numerous in branch wood than in stem wood.
More numerous and narrower rays were measured in branch wood, but had similar lumen
size. Similar cell wall thickness was measured in branch wood as in stem wood of map le
and beech and narrower in the latewood of Scots pine.
The density (at 12% MC) of maple and beech branch wood was higher than that of their
stem wood, with 14% respectively 20%, probably due to the differences in cell size noted
above, while the density of Scots pine branch wood was 19% lower than its stem wood,
probably due to the proportion of juvenile wood in the specimens.
The compression strength of maple branch wood was slightly lower than that of maple
stem wood, beech compression strength was similar for branch and stem wood. This
seemed to correlate with the smaller cell lumens, with a greater number of medullary rays
and a higher proportion of pores in the branch wood. The compression strengths of maple
and beech branch wood were similar, but both were substantially higher than that of Scots
pine branch wood, which was approximately half the strength of stem wood.
The bending strength of maple branch wood was slightly higher and the bending
stiffness slightly lower than maple stem wood, while the MOE for Scots pine branch wood
was approximately a third of the MOE of Scots pine stem wood and its MOR
approximately one half. Comparing maple with Scots pine, the MOE of maple branch wood
was 2.8 times higher and the MOR 2 times higher than that of Scots pine branch wood. The
branch wood density had a clear relationship with the MOR.
As expected, the branch panels with the grain perpendicular to the surface did not
perform as well in bending as other wood based composites reported in the literature. The
MOE was 770 MPa for maple branch panels and 537 MPa for Scots pine panels. The MOR
was 9 MPa for maple panels and 7 MPa for Scots pine panels. The results suggest a
destination of those panels strictly to small decorative eco-products that are not subjected
to bending. This is attributed mainly to the grain orientation of the branch wood panel
rather than to the material.
CONCLUSIONS
There were clear microscopic differences between branch wood and stem wood of all three
species studied. However, since maple and beech branch wood have similar strengths to stem wood
of the same species, they could be used as alternative raw materials for manufacturing furniture
panels. If furniture panels were to be manufactured from Scots pine branch wood, they should be
used in applications that avoid bending stresses.
157
REFERENCES
[1] BS 373 (1957) Methods of Testing Small Clear Specimens.
[2] Cionca M, Zeleniuc O, Gurau L, Olarescu A (2006) Wooden branches. A new approach in
furniture design. Pages 50–57 in Proc. International Science Conference, 5–7 Sept. 2006,
Technical University, Zvolen, Slovakia.
[3] BS EN 310: 1993. Wood-Based Panels. Determination of Modulus of Elasticity in Bending and
of Bending Strength
[4] ISO 3131 (1975) Wood. Determination of Density.
[5] ISO 3787 (1976) Wood. Testing in Compression Parallel to Grain.
158
SOME ASPECTS OF USING POST-CONSUMER WOOD
IN PARTICLEBOARD PRODUCTION
D. Janiszewska*, I. Frąckowiak, C. Andrzejak
Wood Technology Institute, Wood-Based Materials and Glues Department
*
INTRODUCTION
Wood processing increases with economic development, resulting in asteadilyincreasing
number ofdifferent types ofwood waste [1-3]. Increasing timber demands in industrialized
countries, rising capacities of wood processing and shifts of silvicultural strategies (promotion
of hardwood and potential reduction of softwood cultivation) will result in restricted timber
availability and supply, especially for the softwood processing industry. The European woodbased panel industry relies primarily on the softwood timber supply (spruce, pine, fir), hence
these factors may affect the sector. Taking into account the availability of waste wood
(e.g., residues from saw and plywood mills, etc.) and used wood (e.g., old furniture, beams,
etc.), recovered wood assortments are becoming more and more important for the European
panel industry [4, 5].
Current knowledge confirms suitabilityof lignocellulosicwastefor substitution forchips
andwood fibersin particleboard production and moreover it points to thepossibility of theiruse
forthe production of various intended-use composites [6].
The aim of this study was to carry out analysis of post-consumer wood and understand its
impact on the properties of particleboards.
EXPERIMENTAL
Tests were carried out using post-consumer wood chips obtained in industrial conditions
(A1 and A2 classes of waste wood according to Altholzverordnung). Chips from postconsumer wood and particles obtained from this wood were characterised in terms of their
quantity and quality.
Measurement analysis and determination of fraction composition of chips and particles
obtained from post-consumer wood was carried out.
The share of particular assortments within post-consumer wood was determined.
Then three-layer particleboards with different share of post-consumer wood in the inner and
outer layers were produced.
The standard mechanical and physicochemical properties of the panels were examined
as well.
159
ACKNOWLEDGMENT
The research was carried out within the project "Recycling of used Wood in Germany and
Poland" financed within the framework of Polish-German cooperation for sustainable
development by the Ministry of Science and Higher Education (MNiSW) and the German
Federal Ministry of Education and Research (BMBF).
CONCLUSIONS
The results of the studies showed differences within the individual classes of tested material
in the case of both post-consumer wood chips and particles obtained from them.
A dispersion of particular chip measurement was observed. The total share of assortments,
which are the most valuable in terms of particleboards production, such as solid wood,
plywood, particleboards was in the range of 80-90% for both tested portions.
The share of non-wood substances within tested classes of waste wood was insignificant.
REFERENCES
[1] Merl AD, Humar M, Okstad T, Picardo V, Ribeiro A, Steierer F (2007) Amounts
of recovered wood in COST E31 countries and Europe. 3rd European COST E31 Conference:
Managemenet of Recovered Wood, Klagenfurt, Austria, 79-117
[2] Ratajczak E, Szostak A, Bidzińska G(2003) Drewno poużytkowe w Polsce, Wood
Technology Institute
[3] Szostak A, Ratajczak E, Bidzińska G, Gałecka A (2004) Rynek przemysłowych odpadów
drzewnych w Polsce, WOOD. Research papers. Reports. Announcements 172:69-90
[4] Czarnecki R, Dziurka D, Łęcka J (2003) The use of recycled boards as the substitute
for particles in the centre layer of particleboards, EJPAU 6(2)
[5] Kearley V, Goroyias G (2004) Wood panel recycling at a semi-industrial scale. Proceedings of
the 8th European Panel Products Symposium 1-18
[6] Nicewicz D, Danecki L (2009) Wood from pallets and wooden containers as a potential source
of raw material for the wood-based boards industry, Ann. WULS - SGGW, For Wood Technol
69:115-118
160
UP- AND DOWN-CYCLING OF WASTE WOOD IN EUROPE
P. Meinlschmidt* & D. Mauruschat
Fraunhofer Institute for Wood Research - Wilhelm-Klauditz-Institut (WKI)
Bienroder Weg 54E, D-38108 Braunschweig, Germany
*
INTRODUCTION
Wood products at the end of a life cycle are chipped to particles in most European countries
and consequently used for particleboard or for energy production. Unfortunately, quite often
these valuable organic materials are still deposited on waste sites in many countries. The most
economically and ecologically worthwhile reuse of recovered wood without any crosscontamination into the new product will be demonstrated within this presentation.
PROJECT IDEA
Within the actual WoodWisdom project “Cascading Recovered Wood” (CaReWood) the
European consortium will try to avoid chipping all the valuable solid waste wood material into
small particles. Many of the wood products waiting for a second life contain relatively large
dimension timbers of originally good quality that would have a higher value than chipped
particles if their dimensions were maintained during the recycling process. The CaReWood
project will develop and evaluate techniques for converting large dimensions of round wood
into new, large dimension solid wood products to complement the solid wood currently used in
the furniture, interior fitting and construction sectors.
The overall objective of this project is to introduce an up-grading concept for recovered
solid timber as a source of clean and reliable secondary wooden products for the European
industry. This conceptual idea is visualized in Figure 1.
The presentation will explain the current situation of wood recovery in Europe, the potential
of keeping large timber structures by ensuring to keep only the cleaned and free of
contamination wood and produce new products from the old timber.
METHOD OF UP-CYCLING
After choosing the largest dimension waste wood coming either from furniture recycling or
from the demolition site, there must be a pre-sorting by similar dimensions or the same species.
Afterwards, all contaminations have to be removed in a cleaning station. With modern
detection techniques like Field Asymmetric Ion Mobility Spectrometer (FAIMS), X-Ray
Fluorescence Spectroscopy (XRF) or Laser-Induced Breakdown Spectroscopy (LIBS), possible
remaining organic or inorganic wood preservatives will be detected and if necessary the wood
will be cleaned again [1–3]. The absolute contaminant free waste wood pieces will be
subsequently glued in such a way that the new intermediate beams can be used for new
products.
161
Figure 1: Concept of the CaReWood project idea of waste wood up-cycling.
CONCLUSIONS
The presentation will show an up-cycling concept which reaches from the place where wood
waste originates through the sorting and cleaning stations. Afterwards the cleanness of the
material will be tested with different techniques and the wood will be glued together in order to
obtain new intermediate wood beams for new products.
ACKNOWLEDGMENT
Public funding is provided by the national funding body BMEL and the EC in the frame of
the ERA-NET Plus imitative Wood Wisdom-Net+.
REFERENCES
[1] Mauruschat D, Schumann A, Meinlschmidt P, Gunschera J, Salthammer T (2014) Application
of gas chromatography - field asymmetric ion mobility spectrometry (GC-FAIMS) for the
detection of organic preservatives in wood, International Journal for Ion Mobility Spectrometry,
17(1):1-9
[2] Briesemeister R (2013) Analyzing the suitability of X-ray fluorescence (XRF) devices for
detecting foreign material in recovered wood, Diplomarbeit, TU Clausthal
[3] Uhl A, Loebe K, Kreuchwig L (2001) Fast analysis of wood preservers using laser induced
breakdown spectroscopy. Spectrochimica Acta Part B: Atomic Spectroscopy 56(6):795-806
162
WOOD YOU BELIEVE IT? PRO-ENVIRONMENT IS PRO-FORESTRY
L. Ranacher* & T. Stern
Kompetenzzentrum Holz GmbH
Altenbergerstraße 69, Linz, AUSTRIA
*
INTRODUCTION
Acknowledging the versatile use and environmental profile, wood is a promising resource
for the transformation of society towards bio-economy. Despite consumers’ very positive
attitude towards wood products, the public is also worried about its production [1,2]. This is
considered to be the result of an abstract idea of an ideal forest and a lack of knowledge
concerning forest management [3]. The Austrian population for example is a consumer
segment with high standards concerning the geographical and ecological origin of wood [4]. A
few studies [5,6,7] have lately investigated the perceptions of students and young people
towards forest industries, forests and climate change and business ethics in forest industries.
Usually, young and well-educated people (e.g. students) are considered to show above average
environmental awareness.
Although the Austrian population is considered to be very sensitive concerning the state of
forests and ecological principles for wood production, no recent study on the perception of
wood production exists. In order to provide suggestions for the future communication of the
forest-based sector it is crucial to investigate what the Austrian forest-based sector
communicates on the sustainability of wood production and how this is perceived by
environment-aware segments.
RESEARCH DESIGN AND RESULTS
A qualitative content analysis of the existing online communication of 16 selected Austrian
forest sector companies and associations was used to identify topics dealing with sustainability
of wood production. The selection considered company size as well as the main field of
business operation to produce a representative sample of the Austrian forest sector. For the
assessment of the public perception a convenience sample with n=170 was used. The sample
displays an above average level of education with 29% holding a university degree and 42%
being university students. The majority of respondents 55% are aged 30 or under and 37% are
somehow related to the forest-based sector (e.g. profession, education or family). Slightly more
women 54% than men took part in the survey.
To assess the respondents’ environmental awareness, the New Environmental Paradigm
scale [8] was used and respondents were divided along their mean score. The Cronbach alpha
(α=0.762) supports the consistency of the scale. The mean score of 22.7 clearly exceeds
neutrality (36) and “mild agreement” (24). Thus, in terms of the scale, the respondents
surveyed represent an evident pro-environmental position.
Relationships with the forest management items were analyzed with cross tabs and a ChiSquare test. Table 1 illustrates a very positive attitude towards selected items: 70% agree that
forest management contributes to a healthy forest and 48% disagree that forest management
results in a decrease in the forest cover. However, more than 60% are indecisive of whether
Austrian wood comes from ecological sound sources, and 45% call for stricter forest
management regulations to protect the forest. Highly significant, respondents not related to the
163
forest-based sector are frequently indecisive whether wood is from ecological sound sources
(p=0.004).
Table 1: Perception of Austrian forest management based on topics communicated by the forest-based-sector
Items
Disagree
FM* results in a decrease of forest cover
48.2
FM contributes to a healthy and stable forest
14.1
Austrian wood is from ecological sound sources
11.2
Stricter FM regulations are needed
13.5
*forest management
Neutral
22.4
11.8
30.2
20.0
Agree
15.3
70.6
27.8
45.3
I don’t know
14.0
3.5
30.6
21.2
The level of environmental awareness does have an influence on the perception of forest
management but differently than expected. Respondents both not related to the forest-based
sector and with a higher level of environmental awareness, appear to be more forest
management positive. For example, they disagree that forest management decreases the forest
cover (p=0.025) and agree that forest management contributes to a forest health and stability
(p=0.031). Both topics were strongly communicated by the forest sector. However, concerning
the items on ecological sound sources and regulations the two groups do not differ from each
other. Therefore, the results indicate that topics that are less communicated are also less
perceived by environment-aware respondents.
Limitations of the study occur due to the survey sample as well as sample of the content
analysis, which provides only a small insight into the communication of the forest-based sector.
This also affects the formulation of the items, which are based on the content analysis.
CONCLUSIONS
The results show that respondents have a quite positive perception of forest management in
Austria. Surprisingly, the positive perception of forest management is linked to a higher
environmental awareness. This indicates that the sustainability communication of the forestbased sector works better when people show a higher environmental involvement. In contrast,
people who show lower environmental involvement are less receptive to sustainability
communication of the forest-based sector.
ACKNOWLEDGEMENT
The study was funded under the Wood Wisdom era-net and is a result of the research
project “What We Wood Believe - Societal perceptions of the forest-based sector”. Cofinanced by the Austrian Federal Ministry of Agriculture, Forestry, Environment and Water
Management under grant agreement 101002/1.
REFERENCES
[1] Rametsteiner E, Oberwimmer R, Gschwandtl I (2007) Europeans and wood – What do
Europeans think about wood and its uses? Ministerial Conference on the Protection of Forests
in Europe Liason Unit Warsaw, Warsaw
[2] Pauli B, Suda M, Mages V (1998) Das Schlachthausparadox oder das Dilemma der forstlichen
Öffentlichkeitsarbeit. LWF aktuell, 13
[3] European Commission Directorate-General for Enterprise (2002) Perception of the wood-based
industries – qualitative study. Office for Official Publications of the European Communities,
Luxembourg
[4] Weinfurter S, Schwarzbauer P (2011) The Effect of Forest Context on Austrian Consumer
Preferences for Wooden furniture. 4th WoodEMA Conference Kozina Slovenia
164
[5] Amberla T, Wang L, Juslin H, Panwar R, Hansen E, Anderson R (2010) Students' perceptions
of forest industries business ethics - A comparative analysis of Finland and the USA. EJBO, 15
(1). url: http://ejbo.jyu.fi
[6] Lovell R, O'Brien L, (2009) Wood you believe it? Children and young people's perceptions of
climate change and the role of trees woods and forests. Forest Research
[7] Mynttinen S (2009). Young people’s perceptions of the wood products industry – a relational
view. University of Helsinki. Department of Forest Economics
[8] Dunlap RE, Van Liere KD (1978) The new environmental paradigm. J Environ Educ 9(4). doi:
10.1080/00958964.1978.10801875
165
Session III
Innovation Trends, Environment & Markets
Poster Session
GREEN PARTICLEBOARD USING FREE FORMALDEHYDE SOYA
PROTEIN BINDER
A. Shakeri1,*, A. Tahmasbi2 & T. Tabarsa2
1
2
Faculty of Chemistry, University of Tehran, Iran
*
Faculty of Wood and Paper Engineering, Gorgan University of Agricultural sciences and Natural
Resources, Gorgan, Iran
INTRODUCTION
Nowadays, formaldehyde emission (FE) from wood composites during manufacturing and
use is the main concern of environmental agents. Research centers are seeking an alternative
formaldehyde free binder for manufacturing wood composites. Many efforts have been
conducted to omit formaldehyde emission from the panels. Usage of isocyanate and phenol
formaldehyde in producing panel reduced the formaldehyde emission slightly [1]. Ammonium
chloride and phosphoric acid were used as catalysts during the production of particleboard and
the results showed that both catalysts reduced the formaldehyde emission [2]. Particleboard
made using isocyanate resin also reduced formaldehyde emission [3]. Soya flour has been also
considered for producing eco-friendly free formaldehyde plywood [4]. In this study soya
protein was used as a binder for making free formaldehyde particleboard. Wood particles were
provided from a local particleboard company. Soya seeds were provided from a local farm.
Seeds were ground and 100 mesh screened. Soya flour was mixed with water so that the
solidity of mixture reached 25% and was sprayed over the wood particles. Soya flour was
applied 8 and 10% base on the wood particles dried weight. Particles were then dried. A thin
layer of soya protein was formed on the surface of particles. The mixture of epichlorohydrin
and ammonium hydroxide (30% wt) was used as hardening. The mixture was stirred in a hot
water bath at 55°C for 90 minutes. The hardener solution was stirred in a water bath at 75 °C
for one hour and mixed with sodium hydroxide (20% wt) at room temperature for 5 minutes
before application. UF resin at 10% was used for producing control boards. For each
combination (amount of 8 and 10% soya and UF resin) 3 particleboards were manufactured. A
total of 9 samples were cut from each board, to be used in testing of mechanical and physical
properties. The results of analyses of individual properties were thus a mean of 27
measurements. The results of these determinations were subjected to statistical analysis.
Formaldehyde emission (FE) of panels was also examined according to the relevant European
Standards (EN120). The results of evaluations are presented in Table 1.
Table 1: Physical and mechanical properties panels
MOR
(MPa)
MOE
(GPa)
IB
(MPa)
TS
(%)
FE
(mg/l)
Control (UF)
17.71
3.37
0.47
32.6
0.72
8% (Soya)
16.62
3.17
0.47
38.53
0.38
10% (Soya)
19.80
3.60
0.61
29.61
0.52
167
The results showed that internal bond strength (IB), the modulus of rupture (MOR), and the
modulus of elasticity (MOE) of panels made using 10% soya protein increased 12%, 7% and
30% respectively. Thickness swelling decreased by 9% compared with controls. No
formaldehyde emission was observed for panels made using 8% and 10% soya protein while
control panels showed 0.72 mg/l. It seems that soya protein has bonded by functional groups
(C=O, NH, ..) with hydroxyl groups of wood particle surface. In addition, during the making
this adhesive no formaldehyde was used so there is no emission. Finally, it should be noted that
all physical and mechanical properties of panels meet the EN standard. It is suggested that this
adhesive is introduced as a substitution for UF resin in particleboard industry.
CONCLUSIONS
In this study soya protein has been investigated to be used as binder for producing
particleboard. Soya flour was treated with some chemicals. A liquid binder was prepared using
some solvents and sprayed over wood particles. Resonated wood particles were dried and hot
pressed. Formaldehyde emission, physical and mechanical properties of manufactured
particleboard were evaluated and compared with EN standard requirement for particleboard.
Results showed that there is no formaldehyde emitted from boards and physical and
mechanical properties of manufactured particleboards meet the EN standard requirement.
REFERENCES
[1] Rowell, R.M., (2006). Chemical modification of wood for improved adhesion in composites ,
USDA forest service, forest products Laboratory, Madison, Wisconsin
[2] Costa, N.,et al.( 2012). Alternative to latent catalysts for curing UF resins used in the
production of Low formaldehyde emission wood-based panels. International Journal of
Adhesion and, Adhesives. 33 56-60, doi:10.1016/j.ijadh adh.2011.11. 3
[3] Dziurka D., Mirski,R., (2010). UF-PMDI Hybrid resin for waterproof particleboards
manufactured at a shortened pressing time. Drvna Industija.61 (4):245-249
[4] Liu, Y., Li, K., (2007). Development and characterization of adhesives from soy protein for
bonding wood Journal of American Oil chemists adhesion and adhesives, 27:59- 67
168
PLYWOOD: NOVEL SOLUTIONS FOR SUSTAINABLE INDUSTRIAL
PRODUCTION
P. Král* & P. Klímek
*
INTRODUCTION
Plywood is a traditional material. Despite the long-term decline of its overall share of panel
consumption the production in 2011 was stabilized on 4.2 Mio m3 in Europe [1] and nowadays
represents around 6% of production considering wood-based panel industry [2]. In the Czech
Republic we obtained information that company Dyas.eu a.s. (Uherský Ostroh) produces up to
20 000 m3 of beech plywood per year, Wotan Forest a.s. (Solnice) produces up to 30 000 m3
mainly spruce plywood per year and TON a.s. (Holešov) produces molded beech plywood
boards up to 10 000 m3 per year.
Although branch of the plywood industry competes with other materials such as oriented
strand board or laminated particleboard, its superior mechanical properties, appearance or
considerably easy production always find applications in transport, building [3] or furniture
industry. To comply with standards of these applications and remain competitive in this field,
novel solutions in product development using different wood species [4] or process
optimization are proposed to match the needs of producers and customers. In this abstract we
summarize our own approaches, driven by needs of industrial partners.
CORK LAYERED PLYWOOD BOARD
The cork-layered plywood board has two major motivations: (1) Using beech wood in
plywood boards as an alternative to spruce plywood. (2) Development of a lighter alternative
which can compete with commonly used particle-based materials. Two types of cork layered
plywood board were developed. In one, the core of the plywood was substituted by 3 mm cork
sheet and in the other one, the core layer and surface layer were substituted by cork to deliver
alternative appearance (Figure 1).
Figure 1: Cork layered plywood panels; Plywood with cork core (CLP1) and Plywood with cork core and surface
(CLP2)
169
In general, both panel types performed better than oriented strand board in longitudinal
direction (OSB long) and particleboard (PB) although their density was reduced by cork inlay
below 600 kg/m3. The board with cork surface may be introduced to a wider range of
applications, however with lower MOE. Further details are available in [5].
MULTI-SPECIES PLYWOOD BOARDS
In order to decrease density and use beech wood as an alternative to spruce plywood panels,
multi-species plywood boards were developed using spruce and beech veneers. Furthermore,
the plywood boards were produced under two different processing pressures to enhance
properties and observe the effect of densification on the mechanical performance. Interesting
mechanical performance behavior was shown by increased processing pressure where
multilayered plywood showed decrease in properties, while spruce plywood properties were
significantly increased (figure 2). Further details in [4].
Figure 2: MOR and MOE of the plywood panels produced using lower veneers grade
LOW-GRADE VENEERS USED IN PLYWOOD BOARD PRODUCTION
Five-layer plywood panels were prepared using spruce and beech wood. Veneers of a lower
and a higher grade were used. The panels were produced using two processing pressures. Four
different types of the panels in total were produced. Different interactions considering
processing pressures were observed in bending performance in different directions of plywood
board (see figure 3).
Figure 3: MOR and MOE of the plywood panels produced using lower veneers grade under low and high pressures
The study indicates that the processing by the increased pressure is more suitable for the
spruce type of plywood boards where it has a positive effect on the MOR and MOE.
Interestingly, the positive contribution of the densification was even more significant when the
veneers of lower grade were used.
GLASS-FIBRE REINFORCEMENT IN BEECH PLYWOOD
In this research, glass-fiber fabric with basis weight 60 g/m2 (PW60) and 100 g/m2 (PW100)
were used to increase bending properties without significantly increasing the density. The glass
fiber fabric was placed onto both surfaces and covered with water resistant, antiskid foil. The
results were compared with plywood without glass-fiber fabric (see figure 4.)
170
Figure 4: MOR and MOE of the plywood panels produced with glass-fiber reinforcement
The glass fabric successfully increased the bending strength and bending stiffness while
density was maintained on a similar level. Interestingly, the basis weight was not found as the
most important attribute of the fabric when the MOE of PW60 was the same as or even higher
than the PW100. It seems that the type of woven of the fabric in production has a greater effect
on the final properties than its basis weight. These results were used to obtain a utility patent
and helped to develop a new product of the partner company.
CONCLUSIONS
In summary, in last three years we successfully introduced various approaches to make
plywood board more attractive by means of reduced density, increased properties or reduced
costs of production. Various results and conclusions from our research were used and applied
in the Czech Republic plywood industry to help develop further solutions some of which
became industrial secrets or “know-how”.
REFERENCES
[1] Eastin I, Brose I, Novoselov I (2012) UNECE/FAO Forest Product Annual Market Review,
2011-2012. UNECE/FAO For Prod Annu Mark Rev 67–79
[2] UNECE (2013). Forest Products Annual Market Review 2012-2013 Forest Products.
Geneva tim. Geneva: UNECE/FAO Forestry and Timber Section
[3] Bekhta P, Hiziroglu S, Shepelyuk O (2009) Properties of plywood manufactured from
compressed veneer as building material. Mater Des 30:947–53
[4] Král P, Klímek P (2014) Utilization of spruce (Fagus sylvatica L .) wood in plywood
production using different processing pressures. J For Sci 495–499
[5] Král P, Klímek P, Mishra PK, Rademacher P, Wimmer R (2014) Preparation and
Characterization of Cork Layered Composite Plywood Boards. Bioresources 9:1977–
1985.
171
Author’s Alphabetical Index
A
van Acker, J.
Andrzejak, C.
Ayrilmis, N.
154
160
88, 122, 136, 138,140
B
Baar, J.
Bak, M.
Benthien, J.T.
Bicke, S.
de Boever, L.
Borůvka, V.
Böhm, M.
Brabec, M.
Buddenberg, H.
van den Bulcke, J.
Burgert, I.
64, 73, 108
80
60
103
153
119
142
68, 110
84
153
43
C
Cabane, E.
Cionca, M.
43
156
Č
Čech, P.
Čermák, P.
Čop, M.
115
68, 107
35
D
Defoirdt, N.
Dejmal, A.
Děcký, D.
Doubek, S.
Dömény, J.
153
26
21
119
117
E
Eichhorn, S.
van Herwijnen, E.
van Herwijnen, H.W.G.
Hlásková, L.
Hofmann, T.
Horáček, P.
Hughes, M.
Hýsek, Š.
128
133
71
41
56
17, 82
142
J
Janiszewska, D.
19
K
Kaliňáková, B.
Kamke, F.A.
Kammerloher, C.
Kariž, M.
Kaymakci, A.
Klímek, P.
Klímová, H.
Kloiber, M.
Koch, G.
Koiš, V.
Konnerth, J.
Kopecký, Z.
Korolev, A.
Kotradyová, V.
Krahofer, M.
Král, P.
Krenke, T.
Kropacz, A.
Kumar, A.
Kunecký, J.
Kutnar, A.
Kuzman, M.K.
Kúdela, J.
Kvítek, L.
Kwon, J.H.
19
13, 28
84
35
122, 136
130, 169
77, 110
30
33
117
128
71
13
19
128
169
126
100
95
30
13, 28
35
15, 21, 56, 66
108
88, 138, 140
150
L
F
Feng, Y.
Fodor, F.P.
Fojutowski, A.
Frąckowiak, I.
Frybort, S.
37
112
100
62
126
G
Ghorbani, M.
128
Gindl-Altmutter, W.133
Gorišek, Ž.
58
Gryc, V.
56
Gurau, L.
26, 156
H
Hajek, P.
Hapla, F.
Han, T.H.
Helder, S.
95
147, 150
138, 140
60
Lagaňa, R.
Lee, S.H.
Liebner, F.
15
140
128
M
Mahrdt, E.
Mauritz, R.
Mauruschat, D.
Meier, D.
Meinlschmidt, P.
Mihailović, S.
Milch, J.
Militz, H.
Mishra, P.K.
Müller, U.
133
126
161
37
130, 161
110
30, 68
103
43
126
N
Navrátil, M.
Nebehaj, E.
30
41
Németh, R.
Nevrlý, O.
Noponen, T.
Noskowiak, A.
80, 112, 150
73
17
100
Teischinger, A.
Tesařová, D.
Tiňo, R.
Tippner, J.
145
66, 115
19
30, 46, 53, 68,
60, 82
105
Trcala, M.
Troppová, E.
Tywoniak, J.
39
46, 53
95
O
Ohlmeyer, M.
Orel, B.
V
P
Paajanen, O.
Pařil, P.
Paschová, Z.
Pánek, M.
Petrič, M.
Pfungen, L.
Pinkl, S.
Pozsgay, B.
Pori, P.
Prucek, R.
90
108
49
119
105
128
133
112
105
108
R
Rademacher, P.
Ranacher, L.
Rautkari, L.
Riegler, M.
Richter, K.
Rousek, R.
Rowell, R.M.
Ruminski, N.
Ruponen, J.
Ryparova, P.
28, 41, 49, 56
163
82
124
124
26
98
147
82
95
S
Sáblík, P.
Sebera, V.
Selinger, J.
Seppke, B.
Sernek, M.
Schmidberger, C.
Schmitt, U.
Shakeri, A.
Sharapov, E.
Stangierska, A.
Stern, T.
Straže, A.
Svoboda, J.
Sykacek, E.
41
30, 68, 77, 86
93
60
35
133
33
167
13
62
163
58
51
124
Š
Šimek, M.
Škapin, A.S.
Šprdlík, V.
Štrbová, M.
Švehlík, M.
86
105
19, 110
66
53
T
Tabarsa, T.
Tahmasbi, A.
Tauber, J.
75, 167
167
51
Vahtikari, K.
Vilčnik, A.
17
105
W
Wimmer, R.
43, 53, 56, 93, 124,
130, 142
Z
Zabielska-Matejuk, J.
Zeidler, A.
62
119
77, 117
Název publikace:
Vydavatel:
Mendelova univerzita v Brně
Návrh obálky:
Iva Kučerová, ASTRON Studio CZ a.s.
Autor:
prof. Dr. Ing. Petr Horáček a kol
Určeno pro:
účastníky konference
Počet stran:
174
Vydání:
první, 2015
Náklad:
300 ks
Tisk:
ASTRON Studio CZ a.s.
Green Park, Veselská 699, 199 00 Praha 9
ISBN 978-80-7509-255-7

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