Content uploaded by Petar Antov
Author content
All content in this area was uploaded by Petar Antov on Dec 18, 2019
Content may be subject to copyright.
ICWST 2019
30th
PROCEEDINGS
Zagreb, 12th – 13th December 2019
• Faculty of Forestry, University of Zagreb, Croaa • Biotechnical Faculty, University of Ljubljana, Slovenia
• Faculty of Forestry and Wood Sciences, Czech University of Life Sciences Prague, Czech Republic
• WoodEMA i.a. • InnovaWood
IMPLEMENTATION
OF WOOD SCIENCE
IN WOODWORKING
SECTOR
30th
Internaonal
Conference on
Wood Science
and Technology
70th
Anniversary of
Drvna industrija
Journal
ICWST • 2019 • IMPLEMENTATION OF WOOD SCIENCE IN WOODWORKING SECTOR
30th International Conference on Wood Science and Technology - ICWST 2019 “IMPLEMENTATION OF
WOOD SCIENCE IN WOODWORKING SECTOR” & 70th Anniversary of Drvna industrija Journal
18
Possibilities for Manufacturing Eco-friendly Medium Density Fibreboards
from Recycled Fibres – a Review
Antov, Petar1*; Savov, Viktor1
1 Department of Mechanical Wood Technology, Faculty of Forest Industry, University of Forestry, Sofia,
Bulgaria
*Corresponding author: p.antov@ltu.bg
ABSTRACT
The production of medium density fibreboards (MDF) is the second largest worldwide, preceded only
by the production of plywood. A major advantage of this technology is the possibility for utilization of
small-sized and low quality wooden raw material. However, the increased production and the expected
average life cycle of panels of about 15-20 years result in significant amounts of post-consumer wood
waste. Due to the content of synthetic adhesives the panels are not suitable for energy applications. On
the other hand, their recycling and re-use will reduce the consumption of wood raw material.
Significant amounts of lignocellulosic waste and residues also remain in the production and recycling
of paper and cardboard. This article presents a review and analysis of the current state of research in the
field of recycling lignocellulosic fibres and possibilities for their use in the production of MDF panels.
Different methods for recycling with and without the use of chemical reagents in terms of quantitative
yield, quality of panels and production costs, are presented.
Key words: wood-based panels; wood waste, cascading use of wood; recycled fibres; MDF
1. INTRODUCTION
The transition to a circular and low-carbon economy have posed new actions and
requirements towards a greater and more sustainable use of natural resources by sustainably
increasing the primary production and conversion of waste into value-added products, enhanced
production and resource efficiency. To meet these demands actions in a variety of areas are
required, from the sustainable management of forests, to the more resource efficient use of
wood in society (Antov et al., 2018). Cascading use of wood resources, defined as “the efficient
utilisation of resources by using residues and recycled materials for material use to extend total
biomass availability within a given system” is one of the leading principles for achieving this
goal (Stevulova et al., 2016, Vis et al., 2016). The wood-based industries produce significant
amounts of waste and residues. According to Mantau (2012) 26 million tonnes of post-
consumer wood (wood products that are disposed at the end of their life cycle, e.g. wooden
furniture, window frames and wood-based panels, packaging, doors, windows, various
construction materials, etc.) was generated in Europe in 2010. Currently, recovered wood is
used for relatively low value applications including energy generation, particleboard
manufacture, animal beddings and landscape uses (Irle et al. 2019).
Following the European economic recovery, European wood-based composite production
increased by 2.8 % in 2016, to 74.7 million m3 (European Panel Federation, 2017;
UNECE/FAO, 2017). The consumption of fibreboard in Europe increased by almost 1 million
m3 in 2016. The annual consumption of medium-density fibreboard (MDF) in Europe increased
by 15 % in 2016 (Mantanis et al., 2018) as the main consumers of European MDF panels were
furniture (45 %) and laminate flooring (32 %) manufacturers (European Panel Federation,
2017). This increased production and consumption in the recent years could subsequently
generate significant quantities of waste wood-based panels at the end of their service life,
requiring recycling instead of landfilling or incineration, due to the new stricter environmental
30th International Conference on Wood Science and Technology - ICWST 2019 “IMPLEMENTATION OF
WOOD SCIENCE IN WOODWORKING SECTOR” & 70th Anniversary of Drvna industrija Journal
19
legislation (Daian and Ozarska, 2009; Kim and Song, 2014). Moreover, most of the industrially
produced wood composites are made with synthetic adhesives, which are cost-effective and
perform very well regarding bonding performance, mechanical properties, thermal stability and
water resistance (Jin et al., 2010; Jivkov et al., 2013a; Jivkov et al., 2013b; Yang et al., 2015)
but have one major disadvantage, namely the free formaldehyde emissions, especially in indoor
applications. This, together with the growing environmental consciousness related to
sustainability of raw materials and end products has significantly increased the scientific
interest towards the possibilities for recycling waste wood composites. The aim of this paper is
to summarize the current state of research in the field of technologies for recycling waste and
residues from wood composites in order to obtain fibres suitable for the production of MDF.
2. METHODS OF RECYCLING WASTE WOOD PANELS AND PRODUCTION OF
MDF
Recycling used wood composites for their subsequent reuse in the production of new panels
is a complex process which involves the disintegration of wood raw material, selection of an
appropriate adhesive system and optimization of the hot press regime. Therefore, it is essential
to understand the physical and chemical properties of wood and recycled materials, as well as
the interactions between wood, recycled material, adhesive and technological conditions.
Three different principle methods can be applied for disintegration of waste wood panels:
mechanical, thermo-hydrolytic and chemical, and combinations between them (Kharazipour
and Kües, 2007; Lykidis and Grigoriou, 2008; Karade, 2010; Kim and Song, 2014; Roffael,
2002; Roffael et al., 2002; Mantanis et al., 2004; Michanickl and Boehme, 1995a; Michanicki,
1997; Moezzipour et al., 2017a; Moezzipour et al., 2017b; Athanassiadou et al., 2005).
Mechanical disintegration severely damages the structure of wood fibres and the fibres
have poor wettability with urea-formaldehyde resins and phenol-formaldehyde resins, but better
wettability with isocyanate adhesives (Roffael and Schneider, 2003, Hameed et al., 2005). In
addition, disintegration in dry conditions leads to the formation of high quantities of dust and
fine particles and partial charring of surfaces of larger pieces occurs as well (Ihnát et al., 2017).
The thermo-hydrolytic disintegration, which uses steam and pressure to cleave the existing
bonds in wood composites, glued by hydrolysable adhesives, produces better quality fibres than
those of the mechanical disintegration. It is generally performed under pressure in the
temperature range of 120–180 °C (Roffael and Kraft, 2004, Kharazipour and Kües, 2007).
Reclaiming fibres from the waste wood panels and residues with a twin extruder machine
(Athanassiadou et al., 2005), or a thermo-mechanic refiner (Roffael et al., 2010) or a steam
exploder resulted in a reduction of fibre length of about 30 % less than the virgin fibres because
they may be mechanically damaged by the refining devices (Hui et al., 2014; Qi et al., 2006).
A comparison of the physical and mechanical properties of the MDF panels manufactured
with the recycled fibres and the fresh fibres showed that a substitution of 15 % of the virgin
fibres by recycling fibres had no negative effect on the physical and mechanical properties of
the panels, but the replacement of 33 % virgin fibres resulted in a significant decrease in the
physical and mechanical properties (Ju and Roh, 2017; Roffael et al., 2016). MDF
manufactured with higher amounts of recycled fibres (67 and 100 %) could not be produced
without applying the hybrid bonding technology whilst MDF made from 100 % recycled fibres
showed significantly lower thickness swelling values as well as a serious drop in the
formaldehyde release compared with boards made from virgin wood fibres (Roffael et al.,
2016). It was considered this may be due to the effect of morphologic parameters and surface
contamination of the recycled fibres with the expired urea-formaldehyde used as a primary
adhesive in the production of the MDF panels.
30th International Conference on Wood Science and Technology - ICWST 2019 “IMPLEMENTATION OF
WOOD SCIENCE IN WOODWORKING SECTOR” & 70th Anniversary of Drvna industrija Journal
20
The effect of recycled wood fibre content on the properties of MDF were also studied by
Lubis et al. 2018. After preliminary treating of waste MDF panels, the authors used a refiner
and hammer mill to isolate recycled fibres from two softwood tree species. Recycled MDF
panels were fabricated using the obtained refiner and hammer mill recycled fibres at quantities
of 0, 5, 10, 20, 30, 50, and 100 %. The highest internal bond strength of the recycled MDF was
determined at 10 % recycled fibre content, regardless of isolation method and wood species.
The mechanical properties, including modulus of rupture, modulus of elasticity, and screw
withdrawal resistance showed behaviors similar to the internal bond strength with increasing
the content of recycled fibres. However, the thickness swelling, water absorption, and
formaldehyde emission of the new MDF decreased with increasing recycled fibre content. As
a result of the performed statistical analysis it was determined that the minimum of 10 %
recycled fibres can be used to replace virgin fibres without deteriorating the MDF properties.
The improved properties of recycled MDF panels were attributed to the reinforcing effects of
recycled fibres covered with cured resins.
According to a study, conducted by Hwang et al. 2005, replacing virgin fibres with
recycled fibres adversely affected physical and mechanical properties of fibreboard. Bending
properties and dimensional stability were linearly dependent on virgin fibre ratios. All panels
with recycled fibre content above 40 % failed to meet any commercial requirement.
Another study investigated the effects of the addition of recycled fibres obtained from
surface laminated MDF panels with three different materials to the properties of three-layer
recycled MDF (Hong et al., 2018). Three types of surface laminates (low-pressure laminate,
polyethylene terephthalate, and polyester coating) were hammer milled, and then went through
a patent-pending fibre recovery system to obtain the recycled fibres that were added to the core
layer of the new recycled MDF at three contents (10, 20 and 30 %), blended with 12 % urea-
formaldehyde resin to hot-pressing. The best internal bond strength, modulus of rupture and
modulus of elasticity of the new recycled MDF panels were obtained at 20 % recycled fibre
content. The authors reported that increasing the recycled fibre content resulted in reduced
thickness swelling, water absorption, and formaldehyde emission.
Moezzipour et al., 2018 studied the performance of the electrical method in MDF wastes
recycling. To determine the practical aspect of the electrical method, the hydrothermal method
as a known recycling method was also studied. Recycled fibres were analyzed by determination
of the chemical composition of fibre and fibre classification. The results showed that some
changes in the chemical composition of recycled fibres occurred in comparison with the virgin
fibres, especially for the hydrothermal method where lignin content was significantly reduced.
Fibre classification test showed significant reduction in the length of the fibres recycled by
hydrothermal method as compared to other fibres. Investigations of the quality of manufactured
MDF boards showed that the electrical method performed better in comparison with the
hydrothermal method.
The pulp and paper industry generates large quantities of waste lignocellulosic materials
which can be recycled and used for fabrication of MDF panels. Pulp and paper sludge can be
recycled in the manufacture of MDF panels because it contains wood fibres. A comparative
research studied the properties of MDF made from virgin fibres mixed with different pulp and
paper sludge sources (Migneault et al., 2010). The investigated factors were mill pulping
processes, thermal-mechanical pulping, chemical-thermal-mechanical pulping, and kraft
pulping, and percentage of sludge mixed with virgin fibres (0, 25, 50, and 75 %). According to
the reported results the properties of MDF panels decreased mostly linearly with sludge content.
Panel properties negatively correlated with the proportion of non-fibrous material such as ash
and extractives. It was concluded that the amount of sludge that can be incorporated into MDF
without excessive decrease in panel quality depends on the pulping process. At 25 % sludge
content, all panels met the quality requirements for MDF used for interior applications.
30th International Conference on Wood Science and Technology - ICWST 2019 “IMPLEMENTATION OF
WOOD SCIENCE IN WOODWORKING SECTOR” & 70th Anniversary of Drvna industrija Journal
21
Antov et al. (2019) studied the possibilities for utilization of low quality lignocellulosic
paper mill waste, which had undergone only mechanical recycling, in the production of
insulation boards with and without surface layer, using a technology, similar to the production
of dry-process fibreboards. Several design variants of insulation boards with recycled
lignocellulosic fibres were developed and manufactured in laboratory conditions. The main
mechanical properties were determined in order to analyze the possibilities of application of the
boards. It was determined that the experimental boards had very good water resistance and
sound insulation properties. As a typical porous material the boards had better sound insulation
properties at higher sound frequencies. However, the low bending strength values represent an
impediment for standalone application of the boards which can be overcome by surface
treatment with phenol formaldehyde resin or inclusion of a secondary material such as paper or
veneer.
Nourbakhsh et al. (2010), investigated the use of old newsprint fibres as a raw material for
laboratory MDF panels. The authors determined the effect of old newsprint fibres mixed with
virgin aspen fibres and the press time (3, 4, and 5 min) on the properties of MDF panels. Panels
were produced using aspen fibres in surface layer and combination of aspen fibres and old
newsprint fibres in the core layer. The authors concluded that old newsprint can be considered
as a potentially suitable raw material for manufacturing MDF panels without having any
significant adverse influence on the panel exploitation properties.
Recycled fibres still contain cured resin residues and exhibit high formaldehyde emissions
in recycled MDF panels (Roffael et al., 2016). A research, carried out by Lubis et al. 2018
studied the removal of cured urea-formaldehyde resins from MDF panels by hydrolysis, finding
that almost 75 % of cured resins were removed from MDF after acid hydrolysis, 50 % after
neutral hydrolysis, and 25 % after alkaline hydrolysis. This indicates that 25–75 % cured urea-
formaldehyde resins remain in the recycled fibres, depending on hydrolysis conditions.
Grigsby et al. (2014a) investigated the levels of cured urea-formaldehyde resins in MDF
panels by water extraction. The authors reported a significant difference in water extractable
resin components between cured pure resin and that from MDF panels.
The mechanical properties of MDF panels depend on the properties of the wood fibres
(Ganz et al., 2006; Lee et al., 2006), fibre orientation or mat structure (Sliseris et al., 2017), the
adhesive system (Grigoriou, 2000), quantity and distribution of adhesives on fibre surface
(Doosthoseini et al., 2010) as well as hot-pressing technological parameters (Gul et al., 2017).
The fibre length and its distribution are related with fibre bulk density, affecting the
construction of internal mat structure of MDF (Lu et al., 2007; Townshend et al., 2015), and
all mechanical properties could be improved by increasing fibre length (Benthien et al., 2017).
In addition, the morphological and chemical characteristics of the fibres are also major factors
affecting the properties of MDF panels (Grigsby and Thumm, 2004; Roffael et al., 2010).
3. CONCLUSIONS
The technical possibilities to utilize different wood panel waste and residues in new
products determine the physical boundary conditions for cascading use of wood resources.
Despite the presented different methods and technologies for recycling waste wood-based
composites and their reuse in the production of MDF panels, there are still many difficulties
and drawbacks for their wide application at an industrial scale. These technical barriers should
be addressed by future research and development activities aiming to further develop recycling
in wood panel industry, including extensive research on solutions for closing the material loop.
Strong efforts are also needed to address the recent imbalance between material and energy uses
of industrial residues, where more significant potential for wood cascading exists.
30th International Conference on Wood Science and Technology - ICWST 2019 “IMPLEMENTATION OF
WOOD SCIENCE IN WOODWORKING SECTOR” & 70th Anniversary of Drvna industrija Journal
22
Acknowledgements: This research was supported by the project No. НИС-Б-1002/03.2019
‘Exploitation Properties and Possibilities for Utilization of Eco-friendly Bio-composite Materials’,
implemented at the University of Forestry, Sofia, Bulgaria.
Conflicts of Interest: The authors declare no conflict of interest regarding the publication of this
paper.
REFERENCES
Antov, P.; Savov, V.; Neykov, N. (2018): Influence of the Composition on the Exploitation Properties of
Combined Medium Density Fibreboards Manufactured with Coniferous Wood Residues, European
Mechanical Science Journal, vol. 2, issue 4, pages 140-145, e-ISSN 2587-1110, DOI: 10.26701/ems.443891
Antov, P.; Savov, V.; Neykov, N. (2019): Possibilities for Manufacturing Insulation Boards with Participation of
Recycled Lignocellulosic Fibres, Journal Management and Sustainable Development 2019, XXI
International Conference Management and Sustainable Development, Yundola, 2019 (in print)
Athanassiadou, E.; Roffael, E.; Mantanis, G., (2005): Medium density fibreboards (MDF) from recycled fibres.
In: Gallis, D.C.T. (Ed.), 2nd European COST E31 Conference. Bordeaux, France, pp. 248e261.
Benthien, J.T.; Heldner, S.; Ohlmeyer, M., (2017): Investigation of the interrelations between defibration
conditions, fiber size and medium-density fibreboard (MDF) properties. European Journal of Wood and
Wood Products 75 (2), 215e232. https://doi.org/10.1007/s00107-016-1094-2.
Daian, G.; Ozarska, B. (2009): Wood waste management practices and strategies to increase sustainability
standards in the Australian wooden furniture manufacturing sector. Journal of Cleaner Production 17 (17),
1594e1602. https://doi.org/10.1016/j.jclepro.2009.07.008.
Doosthoseini, K., Zarea-Hosseinabadi, H., Moradpour, P., (2010): Low resin medium density fiberboard made
from chemical activated hardwoods fibers. Journal of Indian Academy of Wood Science 7 (1), 36-42.
https://doi.org/10.1007/s13196-011-0008-5.
European Panel Federation (2017): Annual report 2016/2017. Available at: www.europanels.org
Ganz, A.; Kandelbauer, A.; Kessler, W.; Kessler, R.W.; Wimmer, R., (2006): Designing wood fibre morphology
and mechanical properties of fibreboards. Journal of Natural Fibers 3 (2e3), 169-187.
https://doi.org/10.1300/J395v03n02_11.
Grigoriou, A.H., (2000): Straw-wood composites bonded with various adhesive systems. Wood Science and
Technology 34 (4), 355-365. https://doi.org/10.1007/s002260000055.
Grigsby WJ; Carpenter JEP; Sargent R., (2014a): Investigating the extent of urea formaldehyde resin cure in
medium density fibreboard: resin extractability and fiber effects. Journal of Wood Chemistry and Technology
34:225–238
Grigsby, W.; Thumm, A., (2004): Visualisation of UF resin on MDF fibre by XPS imaging. Holz als Roh- und
Werkstoff 62 (5), 365-369. https://doi.org/10.1007/s00107-004-0499-5.
Gul,W.; Khan, D.A.; Shakoor, D.A., (2017): Impact of Hot Pressing Pressure on Medium Density Fiberboard
(MDF) Performance. HAL Archives 1, Hal-01612472. https://doi.org/10.1155/2017/4056360.
Hameed, M.; Behn, C.; Roffael, E. and Dix, B. (2005): Water retention capacity of recycling chips and chips
derived directly from wood. European Journal of Wood and Wood Products, 63(5), 390–391
Hong, MK; Lubis M.A.R.; Park, BD; Sohn CH & Roh, J. (2018): Effects of surface laminate type and recycled
fiber content on properties of three-layer medium density fiberboard, Wood Material Science & Engineering,
DOI: 10.1080/17480272.2018.1528479
Hui, W., Xiang-Ming, W., Alpha, B., Jun, S., (2014): Recycling wood composite panels: characterizing recycled
materials. BioResources 9 (4), 7554e7565.
Hwang, CY; Hse, CY; Shupe, Todd F. (2005): Effects of recycled fiber on the properties of fiberboard panels.
Forest Products Journal Vol. 55(11): 60-64
Ihnát, V.; Lübke, H.; Russ, A.; Borůvka, V. (2017): Waste agglomerated wood materials as a secondary raw
material for chipboards and fibreboards. Part I. preparation and characterization of wood chips in terms of
their reuse, Wood Research 62(1): 45-56
Irle, M.; Privat, F.; Couret, L.; Belloncle, C.; Déroubaix, G.; Bonnin E. & Cathala, B. (2019): Advanced recycling
of post-consumer solid wood and MDF, Wood Material Science & Engineering, 14:1, 19-23, DOI:
10.1080/17480272.2018.1427144
Jin, Y.; Cheng, X.; Zheng, Z. (2010): Preparation and characterization of phenol-formaldehyde adhesives modified
with enzymatic hydrolysis lignin. Bioresource Technology, 101, 2046–2048
Jivkov, V.; Simeonova, R. & Marinova, A. (2013b): Influence of the veneer quality and load direction on the
strength properties of beech plywood as structural material for furniture. Innovations in Woodworking
Industry and Engineering Design. Volume 02. 86-92
30th International Conference on Wood Science and Technology - ICWST 2019 “IMPLEMENTATION OF
WOOD SCIENCE IN WOODWORKING SECTOR” & 70th Anniversary of Drvna industrija Journal
23
Jivkov, V.; Simeonova, R.; Marinova, A., Gradeva, G. (2013a): Study on the gluing abilities of solid surface
composites with different wood based materials and foamed PVC, Proceedings of the 24th International
Scientific Conference Wood is Good – User Oriented Material, Technology and Design, ISBN: 978-953-
292-031-4, pp. 49-55
Ju, S.G.; Roh, J., (2017): Manufacture of dyed recycling wood fiber using waste MDF. Journal of The Korean
Wood Science and Technology 45 (3), 297-307
Karade, S.R. (2010): Cement-bonded composites from lignocellulosic wastes. Construction and Building
Materials 24 (8), 1323e1330. https://doi.org/10.1016/j.conbuildmat.2010.02.003.
Kharazipour A.; Kües U. (2007): Recycling of wood composites and solid wood products. In: Wood production,
wood technology, and biotechnological impacts. Universitätsverlag Göttingen, Germany, pp 509–533
Kim, M.H.; Song, H.B. (2014): Analysis of the global warming potential for wood waste recycling systems.
Journal of Cleaner Production 69, 199e207. https://doi.org/10.1016/j.jclepro.2014.01.039.
Lee, S.; Shupe, T.F.; Hse, C.Y., (2006): Mechanical and physical properties of agro-based fiberboard. Holz als
Roh- und Werkstoff 64 (1), 74e79. https://doi.org/10.1007/s00107-005-0062-z.
Lu, J.Z.; Monlezun, C.J.; Wu, Q.; Cao, Q.V., (2007): Fitting Weibull and lognormal distributions to medium-
density fiberboard fiber and wood particle length. Wood and Fiber Science 39 (1), 82-94.
Lubis MAR; Hong MK; Park BD, (2018): Hydrolytic removal of cured urea-formaldehyde resins in medium-
density fiberboard for recycling. Journal of Wood Chemistry and Technology 38(1):1–14
Lubis, M.A.R.; Hong, MK.; Park, BD.; Lee S-M. (2018): Effects of recycled fiber content on the properties of
medium density fibreboard. European Journal of Wood and Wood Products 76: 1515.
https://doi.org/10.1007/s00107-018-1326-8
Lykidis C.; Grigoriou A., (2008): Hydrothermal recycling of waste and performance of the recycled wooden
particle-boards. Waste Management 28(1):57–63
Mantanis, G. I.; Athanassiadou E. T.; Barbu, M. C. and Wijnendaele, K. (2018): Adhesive systems used in the
European particleboard, MDF and OSB industries. Wood Material Science & Engineering, 13(2), 104–116
Mantanis, G.; Athanassiadou, E.; Nakos, P.; Coutinho, A., (2004): A new process for recycling waste fiberboards.
In: Proceedings of the XXXVIII International Wood Composites Symposium. Pullman, USA, pp. 119 - 122.
Mantau, U. (2012): Wood Flows in Europe. Commissioned by CEPI: Confederation of European Paper Industries,
and CEI-Bois: European Confederation of Woodworking Industries
Michanicki, A., (1997): Recovery of fibers and particles from wood-based products. In: Proceedings of the Forest
Products Society Conference on Use of Recycled Wood and Paper in Building Applications. Madison, USA,
pp. 115 - 119
Michanickl, A. & Boehme, C. (1995a): Process for recovering chips and fibres from residues of timberderived
materials, old pieces of furniture, production residues, waste and other timber-containing materials. European
patent, EP 0 697 941 B1
Migneault, S.; Koubaa, A.; Nadji, H.; Riedl, B.; Zhang, SY.; Deng, J. (2010): Medium-density fiberboard produced
using pulp and paper sludge from different pulping processes. Wood and Fiber Science, 42(3), pp. 292-303
Moezzipour, B.; Abdolkhani, A.; Doost-hoseini, K.; Ramazani S.A., A; Tarmian, A., (2018): Practical properties
and formaldehyde emission of medium density fiberboards (MDFs) recycled by electrical method. European
Journal of Wood and Wood Products. 76. DOI: 10.1007/s00107-018-1291-2.
Moezzipour, B.; Abdulkhani, A.; Hoseini, K.D.; Ahmad Ramazani Saadat, A.; Tarmian, A., (2017a): Investigation
the Quality of Recycled Medium Density Fiberboards (MDF) via Two Different Method i.e. Hydrothermal
and Ohmic Heating (Persian). Iranian journal of Wood and Paper industries 8 (2), 323e333.
Moezzipour, B.; Ahmadi, M.; Abdolkhani, A.; Doosthoseini, K., (2017b): Chemical changes of wood fibers after
hydrothermal recycling of MDF wastes. Journal of the Indian Academy of Wood Science 14 (2), 133e138.
https://doi.org/10.1007/s13196-017-0198-6
Nourbakhsh, A.; Ashori, A.; Jahan-Latibari, A., (2010): Evaluation of the Physical and Mechanical Properties of
Medium Density Fiberboard Made from Old Newsprint Fibers. Journal of Reinforced Plastics and
Composites, 29(1), 5–11. https://doi.org/10.1177/0731684408093972
Qi, H., Cooper, P.A., Wan, H., (2006): Effect of carbon dioxide injection on production of wood cement
composites from waste medium density fiberboard (MDF). Waste Management 26 (5), 509e515.
https://doi.org/10.1016/j.wasman.2005.04.010
Roffael E.; Behn C.; Schneider T.; Krug D., (2016): Bonding of recycled fibres with urea-formaldehyde resins.
International Wood Products Journal 7(1):36–45
Roffael, E. (2002): Method for use of recycled lignocellulosic composite materials, US Patent Application
#20020153107A1
Roffael, E. and Kraft, R. (2004): For the thermohydrolytic degradation of UF resins in chipboard. Holz als Roh-
und Werkstoff, 62(2), 155–156
Roffael, E. and Schneider, T. (2003): Investigation on partial substitution of strands in oriented strand boards
(OSB) by different lignocellulosic raw materials. Institute for Wood Biology and Wood Technology. Georg
August University of Göttingen, Busgenweg
30th International Conference on Wood Science and Technology - ICWST 2019 “IMPLEMENTATION OF
WOOD SCIENCE IN WOODWORKING SECTOR” & 70th Anniversary of Drvna industrija Journal
24
Roffael, E.; Behn, C.; Schneider, T.; Krug, D. (2016): Bonding of recycled fibres with urea-formaldehyde resins.
International Wood Products Journal 7 (1), 36e45. https://doi.org/10.1080/20426445.2015.1131918.
Roffael, E.; Dix, B.; Behn, C.; Bär, G., (2010): Use of UF-bonded recycling particle- and fibreboards in MDF-
production. European Journal of Wood and Wood Products 68 (2), 121-128. https://doi.org/10.1007/s00107-
009-0376-3.
Roffael, E.; E. Athanassiadou, and G. Mantanis. (2002): Recycling of particle- and fiberboards using the extruder
technique. In: Proc. of the 2nd Conference on Environ-mental Protection in the Wood Industry
(Umweltschutzin der Holzwerkstoffindustrie). pp. 56-65. University of Göttingen, Göttingen, Germany
Sliseris, J.; Andrä, H.; Kabel, M.; Dix, B.; Plinke, B., (2017) Virtual characterization of MDF fiber network.
European Journal of Wood and Wood Products 75 (3), 397e407. https://doi.org/10.1007/s00107-016-1075-
5.
Stevulova, N.; Schwarzova, I.; Hospodarova, V.; Junak, J.; Briancin J. (2016): Recycled cellulosic fibers and
lignocellulosic aggregates from sustainable building materials. International Journal of Civil and
Environmental Engineering, Vol:10, No:6, available online at [http://scholar.waset.org/1999.3/10004634]
Townshend, E.; Pokharel, B.; Groot, A.; Pitt, D.; Dech, J.P., (2015): Modeling wood fibre length in black spruce
(picea mariana (Mill.) BSP) based on ecological land classification. Forests 6 (10), 3369-3394.
https://doi.org/10.3390/f6103369.
UNECE/FAO (2017): Timber database. Available at: www.unece.org/forests/fpm/onlinedata
Vis M.; U. Mantau; B. Allen (Eds.) (2016): Study on the optimised cascading use of wood. No
394/PP/ENT/RCH/14/7689. Final report. Brussels 2016. 337 pages
Yang, S.; Zhang, Y.; Yuan, T.Q.; Sun, R.C. (2015): Lignin–phenol–formaldehyde resin adhesives prepared with
biorefinery technical lignins. Journal of Applied Polymer Science; 132(36)
