Proceedings of the 55th International Convention of Society of Wood Science and Technology
August 27-31, 2012 - Beijing, CHINA
Application of Recycled Polyethylene In Combination With
Urea-Formaldehyde Resin To Produce Water Resistant
Particleboard
A. Kargarfard
A. Jahan-Latibari
Associate Prof., Wood and Forest Products Science Research Division,
Research Institute of Forests and Rangelands,Tehran, Iran
e-mail: [email protected]
A. Jahan-Latibari
Associate Prof., Department of Wood and paper Science and Technology,
Karaj Branch, Islamic Azad University,
Karadj. IRAN
Abstract
Furniture grade particleboard always suffers from severe thickness swelling and water absorption
which limits its utilization in humid places such as bathrooms, and those countries which do not
produce water resistant panels are faced with this deficiency. To overcome such limitation,
addition of recycled polyethylene (PE) in the surface layer of three layers particleboard was
investigated. The content of UF resin used in the surface was 4% and one of the three levels (5,
10 and 15%) of recycled polyethylene and in the core layer 10% urea formaldehyde resin was
applied. Three layers boards were produced applying press temperature of 185  C and 6 minutes
pressing time. Boards were condition in a standard conditioning chamber, and then tested
according to EN standard. When 5 recovered PE was added to surface layer, MOR and MOE
were increased marginally, but at 15% addition of recovered PE to the surface layer, MOR was
almost doubled and the MOE was increased by 50% compared to control boards. IB was
improved as well and the value of 0.326 MPa. for control boards was raised to 0.537 and 0.466
MPa. for boards produced applying 10 or 15% PE and 4% UF resin respectively. As expected,
both thickness swelling and water absorption were reduced to almost one third of the relevant
values for control boards.
Keywords: Particleboard, Polyethylene, MOR, MOE, IB, thickness Swelling, Water Absorption
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Proceedings of the 55th International Convention of Society of Wood Science and Technology
August 27-31, 2012 - Beijing, CHINA
Introduction
Development, production and consumption of wood based panels initiated more than half a
century ago and during this period, not only the production capacity was expanded, but in
addition to particleboard which was the original product of this category. New products such as
MDF, oriented Strand Board (OSB) and waferboard have been developed and presented to the
consuming market. This wide range of products have provided the opportunity for the
development of new consumer products as well as engineering products applications, thank to
the sustainability of these products. However, an intensive competition exists among these
products and products such as Medium Density Fiberboard (MDF) in furniture industry and OSB
in construction field gained the upper hand (Regattieri and Bellomi 2009). Even though,
particleboard had lost its initial fast growth, but it is still having a good share of the market,
thanks to advances in production technology, utilization of wider range of raw material and cost
saving.
During recent decades, new generation of composite material called WOOD Plastic Composite
(WPC) combining wood and polymers as the main raw materials have been developed and used
and this segment has witnessed a fast growth in wood based panel products (Youngquist 1995).
Due to the presence of hydrophobic polymers, the dimensional stability of these products are
superior. The application of recovered plastic in the production of wood plastic composite also
helped to protect our environment. The research in this field points to the potential of this
technology in the production of particleboard which usually uses larger size wood particles and
employing the flat press technology (Borysiuk et al 2010, Hu et al. 2005). In this respect, waste
thermoplastic are used as the binder (Borysiuk et al. 2011) which not only provides the chance of
using waste material as a source of cheap binder but also reduces the environmental pollution by
eliminating the plastic from the environment (Ayrilmis et al. 2008).
Lignocellulosic materials such as wood or other sources and the formaldehyde synthetic resins
are the two main components in wood based panel production. Even though the swelling of
resins is insignificant compared to lignocellulosic substances, but the content of resin is limited
and does not play a major role in the swelling behavior of wood based panels (Medved et al.
2011). In addition, the concern on the formaldehyde emission for conventional wood based
panels resin necessitated the development of the alternative bonding technology to easier
bonding of wood particles without adverse affect of both quality of the final product and the cost
(Jost and Sernek 2009).
Considering the fact that, to reduce the production cost, improve the quality of the particleboard
product, and utilize the recovered waste thermoplastic in a value added product, the objective of
our work is focused on the application of recovered waste polyethylene in the surface layer of
three layer particleboard to reach better dimensional stability of the product, save the production
cost and reduce the formaldehyde emission. The results are compared with normal furniture
grade particleboard.
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Proceedings of the 55th International Convention of Society of Wood Science and Technology
August 27-31, 2012 - Beijing, CHINA
Experimental
Material
Eucalyptus cameldulensis wood was harvested from a plantation in the northern city of Gonbad,
Iran and after felling, the bolts were transferred to Wood and Paper Laboratory for further
processing. The bolts were first chipped using drum chipper (Pallmann PHT 120x430 and then
flaked in a ring flaker (Pallmann PZ8) to be used in board making. Particles were dried using
rotary drum dryer at 120  C to final moisture content of one percent. Dried particles were packed
in polyethylene bags until used.
Urea-formaldehyde (UF) resin at 63% solid, specific gravity, viscosity, gel time and pH of 1.26
g/cm3, 69 seconds,81 seconds and 8.15 respectively was supplied by local resin manufacturing
plant. Reagent grade ammonium chloride was used as harder. Waste polyethylene was purchased
from local collection company and was first milled to 5 millimeter granules and then in a second
grinder to the final size of about 50 microns.
Three layer boards were produced. The core layer was made applying 10% (based on the oven
dry weight of the particles) UF resin and the surface layer with a combination of 4% (based on
the oven dry weight of the particles) UF resin and one of the three dosages (5, 10 and 15% based
on the dry weight of the particle) of polyethylene.
Board Making and Testing
Core layer particles were blended with UF resin and surface layer was also blended with UF
resin utilizing rotary drum blender and spray nozzle and then the polyethylene particles were
sprayed on the resin blended particles. Then core and surface layers particles were hand formed
using wooden mold. Board target density and thickness was selected at 750 kg/cm3 and 15
millimeters. Mats were pressed at 185  C for 6 minutes in a laboratory press (Buerkle L100)
applying 30 bar specific pressure, five millimeters per seconds closing speed.
Three boards for each combination of variables and total of 27 boards were produced. Test
samples were prepared from each board according to relevant EN standards. MOR and MOE
was measured according to EN310/1996, Internal bonding (IB), EN319/1996 and dimensional
changes, EN 317/1996 standards.
Results and Discussion
In recent decades, the concern on discharge of different plastic containing residues to our
environment has been steadily increasing due to the expanding trend on the application and
utilization of plastic packaging (Ayrilmis et al. 2008). Therefore, various research groups around
the globe have been concentrating to find the application for waste plastics, among them using
these plastic as partial substitute for conventional wood based panel synthetic resins. Wood
plastic composites have been the first alternative for the utilization of waste plastic and
particleboard production has also been investigated.
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Proceedings of the 55th International Convention of Society of Wood Science and Technology
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The results of strength and thickness swelling measurement on particleboard produced using
different combinations of UF resin and recovered polyethylene are illustrated in Figures 1-3.
Each value in Figures 1-3 is the average of 12 measurements (three replicate boards for each
combination of variables and four sets of samples from each board). Similar properties of
homogenous particleboard produced using 10% UF resin is also shown in Figures 1-3 for
comparison.
Boards produced applying different dosages of recovered polyethylene exhibited higher flexural
strength (Fig.1). Application of different content of polyethylene in the particleboard furnish also
improved the IB of the boards compared with the control boards (Fig. 2).
A
B
Figure 1- The influence of recovered PE dosage on MOR (A) and MOE (B) of particleboard
Both 2 and 24 hours thickness swelling and water absorption of the boards containing PE was
lower than control boards, which indicate the potential of hydrophobic PE to impart water
repellency (Figs. 3 and 4).
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Figure 2- The influence of recovered PE dosage on the IB of particleboard
A
B
Figure 3- The influence of recovered PE dosage on 2 hr (A) and 24 hr. (B) thickness swelling of
particleboard
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Proceedings of the 55th International Convention of Society of Wood Science and Technology
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A
B
Figure 3- The influence of recovered PE dosage on 2 hr (A) and 24 hr. (B) water absorption of
particleboard
We have investigated the application of recovered polyethylene as substitute for synthetic resin
in the production particleboard to find the suitability of this material as a cheap source of binder
and also to improve the performance of the product especially its water repellency. Conventional
UF bonded panels are sensitive to moisture and therefore, its application is limited to dry
climate. However, if the recovered PE is used in the surface layer of the boards, then the water
repellency of the product will improve and lower thickness swelling and water absorption is
reached. The flexural strength and modulus as well as the internal bonding of the panels not only
deteriorated but were improved as well. This indicates that to reduce the cost of production and
find new sources of raw material for an industry under pressure, waste materials such as
recovered plastics can be viable material.
Conclusion
Particleboard production and marketing is under intense pressure from competitor both
technologically and cost. Therefore, various measures have been undertaken to improve the
performance of the particleboard in different applications and to reduce the production cost. One
major limitation of conventional particleboard is it water absorbency with limits its application in
humid locations. In this respect, utilization of hydrophobic materials such plastics will help to
improve the water repellency of the final product. Application of different amount of recovered
polyethylene in combination of lower amount of UF resin revealed that using even 5% recovered
polyethylene in the surface layer will reduce both thickness swelling and water absorption of the
particleboard.
Partial substitution of cheap source of recovered polyethylene in the production of particleboard
will reduce the production cost and helps this panel to remain competitive in tense situation
presently the type of panels are faced.
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Proceedings of the 55th International Convention of Society of Wood Science and Technology
August 27-31, 2012 - Beijing, CHINA
Utilizing recovered polyethylene in the surface layer not only do not scarify the strength
properties of the final board, but also improve these properties.
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