BMFB 4713 GREEN MATERIALS & BIOMATERIALS - Introduction of Wood Plastic Composite (WPC) - Advantages of WPC - Disadvantage s of WPC - Testing of WPC - Process to Fabricate WPC - Conclusion

1. COURSE: 4 BMFG
SUBJECT: BMFB 4713 GREEN MATERIALS & BIOMATERIALS
ASSIGNMENT TITLE: WOOD PLASTIC COMPOSITE (WPC)
GROUP MEMBERS:
NO NAME MATRIC NUM SECTION
1 CARRON TING SHUANG SIA B051410115 2
2 TAN BOON YEE B051410099 2
3 NURUL NAJIHAH BINTI SAFIAN SHAH B051410213 3
EVALUATED BY: DR. ZALEHA BINTI MUSTAFA

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TABLE OF CONTENTS
No Contents Page
1 Introduction of Wood Plastic Composite (WPC) 1-3
2 Advantages of WPC 4
3 Disadvantage s of WPC 5
4 Testing of WPC 6-8
5 Process to Fabricate WPC 9-17
6 Conclusion 18

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1.0 Introduction of Wood Plastic Composite (WPC)
Wood-plastic composites (WPCs) are composite materials made of wood fiber or
wood flour and thermoplastics. Notwithstanding wood fiber and plastic, WPCs can likewise
contain other ligno-cellulosic as well as inorganic filler materials. WPCs are a subset of a
bigger classification of materials called normal fiber plastic composites (NFPCs), which may
contain no cellulose-based fiber fillers, for example, mash filaments, shelled nut bodies,
bamboo, straw, digestate, and so on. Concoction added substances appear to be for all intents
and purposes "imperceptible" in the composite structure. They accommodate combination of
polymer and wood flour while encouraging ideal preparing conditions. As of late, individuals
in the ground surface industry begins alluding to WPC as a sort of floor that has an essential
structure of best vinyl polish in addition to an inflexible expelled center. WPC is presently a
built up item class inside LVT. This kind of WPC is not quite the same as the WPC decking
and isn't planned for outside use. Wood-plastic composites are still new materials with
respect to the long history of characteristic timber as a building material. The broadest
utilization of WPCs in North America is in open air deck floors; however it is additionally
utilized for railings, wall, arranging timbers, cladding and siding, stop seats, embellishment
and trim, window and door jambs, and indoor furniture. Wood-plastic composites were first
brought into the decking market in the mid-1990s. Manufacturers guarantee that wood-plastic
composite is more ecologically well-disposed and requires less support than the options of
strong wood treated with additives or strong wood of decay safe species. These materials can
be shaped with or without reproduced wood grain points of interest.

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1.1 Properties of WPC
WPCs are true composite materials and have properties of both materials of plastic
and wood. They have stiffness and strength between those for plastic or wood, but the density
is generally higher than either. The properties of WPCs come directly from their structure:
they are intimate mixes of wood particles and plastic. The plastic effectively coats the wood
particle as a thin layer. The structure is shown at left. The high moisture resistance of WPCs
(water absorption of 0.7% compared to 17.2% for pine) is a direct result of the structure.
Moisture can only be absorbed into the exposed sections of wood and is not transmitted
across the plastic boundaries. The result is that WPCs are extremely moisture resistant, have
little thickness swell in water and do not suffer from fungal or insect attack. The properties of
WPCs can be tailored to meet the product requirements by varying the type of wood or the
type of plastic- the PE based products are cheaper and have a higher heat distortion
temperature than the PVC based products but the PVC products are easier to paint and post
treat. Pigments, UV stabilisers and fire retardants can all be added to the WPC raw material
before extrusion to improve specific properties.
WPCs have:
 Good stiffness and impact resistance.
 Dimensional stability.
 Resistance to rot.
 Excellent thermal properties.
 Low moisture absorption.

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1.3 Applications of WPC
Current applications for WPCs are largely in finished products such as decking,
cladding and window frames. A particular growth area is in structural engineering
applications that use the physical properties of WPC to the limits.
WPCs can be used for products traditionally manufactured from timber and PVC-U and
typical applications are:
 Door frames and components
 Window frames and components
 Exterior vertical and horizontal cladding
 Fascias, sofits and barge boards
 Decking, docks and railings
 Skirting board
 Stairs and hand rails
 Coving
 Balustrades
 Work tops
 Planking and pre-finished floorboards
 Shelving
 Cable trunking
 Fencing and fence posts.
 Garden furniture and architecture.
 Kitchen cabinets and worktops
 Office furniture
 Sound proofing cladding

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2.0 Advantages of WPC
WPCs can produce the final shape through extrusion processing. This maximizes
resource efficiency and gives design flexibility for improved fastening, stiffening,
reinforcement, finishing and joining. WPCs are wood products that need no further
processing. WPCs are weather, water and mould resistant for outdoor applications where
untreated timber products are unsuitable. WPCs are plastic products with exceptional
environmental credential and performance. WPCs have a wide range of applications. They
can cost-effectively replace wood products in applications such as furniture, doorframes, and
decorative profiles, in fact anywhere wood shapes are used. They can cost-effectively replace
plastic products in applications such as window frames, cable trunking, roofline products and
cladding, in fact anywhere that plastics shapes are used.
WPCs have many benefits:
 They are true hybrid materials and combine the best properties of both wood
and plastics.
 They use low cost and plentiful raw materials. Wood waste and recycled
plastics become assets instead of liabilities.
 They are competitively priced and are competitive with traditional materials
such as timber, MDF and PVC-U.
 They are easily produced and easily fabricated using traditional wood
processing techniques.
 They are available in a broad range of finishes and appearances.
 They are easily recycled after use.

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3.0 Disadvantages of WPC
1. Moisture sorption, high swelling
Moisture sorption in other word is the ability to absorb water.
Wood is a hydrophilic porous composite of cellulose, lignin, and hemicellulose
polymers that are rich in functional groups such as hydroxyls, which readily interact
with water molecules by hydrogen bonding. For this reason, WPCs have potential to
take up water under humid conditions due to the presence of numerous hydroxyls. For
WPC, the initial moisture content (MC) is very low and the rate of sorption is very
slow. However, the moisture in the composites is not uniformly distributed through
the cross section and the outermost part or surface of WPC can reach a very high
moisture level which is high enough to support fungal degradation. Even if moisture
uptake is slow in WPCs, but when immersed in water, the uptake may continue over a
long period of time. The rate and extent of moisture sorption increase when the wood
content exceeds approximately 50% of the total weight of the composite. In addition,
a moist environment will cause the wood particles close to the surface swelling, and
the particles will shrink upon drying. This will cause stresses within the material and
create micro cracks.
2. Biological degradation
WPC has the risk of attack by micro-organisms due to it consists of wood particle.
Therefore, degradation by fungi and other micro-organisms may occur and the
condition is speed up due to its moisture sorption. WPC is susceptible to degradation
by UV radiation. Once the degradation of WPC is happened, there is a mass loss in
WPC which will make the material become weak and not able to support high load.
3. Low strength and stiffness, low dimensional stability
WPC has lower strength and stiffness than wood. Therefore, it exhibits a brittle
behaviour, when in comparison with solid wood and glass fibre reinforced plastics.
The strength and stiffness may reduce due to the degradation. It may not be suitable
for use in those parts of places that have large seasonal changes in atmospheric
moisture because of high dimensional changes of wood.

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4.0 Testing of WPC
1. Moisture sorption test
The purpose to moisture sorption is to test and compare the ability of water absorption
of WPC which are different from size, thickness, surface defects and manufacturing
methods.
- Dry the sample specimens of WPC in the oven at 100°C to obtain the constant
weight.
- Then, immerse the sample specimens into distilled water at room temperature. (Or
expose the sample specimens at climate condition set at 90% humidity)
- Weigh the specimens periodically to obtain weight gain over time.
- If the greater the weight gain, the higher the moisture uptake.
2. Weathering test
Plastic and wood will undergo degradation when exposed to atmosphere, and the
degradation rate is speed up if there are changes in weather. WPC will undergo the
similar condition too.
Weathering test is used to determine the changes of WPC when exposed to climate
changes by observing the surface colour change, surface integrity and change in
moisture content.
- The testing is carry out by using the accelerated weathering chamber.
- First, expose the WPC sample with 8 hours of UV light at 60°C.
- Then, condensation at 50°C for 4 hours, 4 hours of water immersion, and 4 hours
drying at room temperature.
- Repeat the cycles for a couple of time, at the same time observe the changes occur
on the WPC samples.

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Figure 3.1: Result of the WPC sample after the weathering test.
From the Figure 3.1, the surface of the WPC sample has changed to deeper colour.
We can observe that the surface is became moisture and cracking or defects are
formed at the surface.
3. Compression test (Biological Decay Test) by terrestrial microcosms (TMCs)
The decay test is used to identify the effect of fungal activity on the WPC such as
mass loss. WPC has showed a limited resistance to fungal growth.
- The WPC samples are inserted or buried into the test soils and sterilized test soil
for a certain time. Three different test soils are used in the TMC tests, TMC1 is a
compost soil with a high activity of soft rot, TMC2 was a soil which dominates by
brown-rot decay, and TMC3 is a forest soil with high activity of white-rot decay.
- Once the WPC samples are removed from the test soils, dry the samples at 50 °C
in oven, after which weigh the samples and calculate the mass loss. The mass
losses of the samples from the sterile soils are used to calculate the corrected mass
loss, or mass loss solely caused by the biological degradation.
- The mass loss of each sample is compared.

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-
Figure 3.2: Set up of TMCs testing
4. Compression test
A compression test is a test in which a material experiences opposing forces that push
inward upon the specimen from opposite sides or is otherwise compressed,
“squashed”, crushed, or flattened. This test is used to determine the compression
strengths of WPC products using ASTM D7031 (Standard Guide for Evaluating
Mechanical and Physical Properties of WPC Products) with the principles of ASTM
D4761 (Standard Test Methods for Mechanical Properties of WPCs) (Arnandha et al.,
2017).
- The WPC specimen is loaded at a prescribed rate until failure occurs or a
preselected load is reached
- The WPC test sample is generally placed in between two plates that distribute the
applied load across the entire surface area of two opposite faces of the test sample
(Figure 3.3).
- Then the plates are pushed together by a universal test machine causing the
sample to flatten.
- The compressed sample is shortened in the direction of the applied forces and
expands in the direction perpendicular to the force.
- The compression strengths of the samples are recorded and will be used to
compare.

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Figure 3.3 Schematic of compression test on WPC (Arnandha et al., 2017).
5. Tensile test
Tensile Testing of materials is a destructive test process that provides information
about the tensile strength, yield strength and ductility of the material. This test is used
to determine the tensile strengths of WPC products using ASTM D7031 (Standard
Guide for Evaluating Mechanical and Physical Properties of WPC Products) in
accordance with ASTM D1037 (Standard Test Methods for Evaluating Properties of
Wood-base Fiber and Particle Panel Materials) (Arnandha et al., 2017).
- The WPC specimens for this test are shaped as shown in Figure 3.4a.
- Each WPC specimens are prepared for test as shown in Figure 3.4b.
- The test sample is securely held by top and bottom grips attached to the tensile or
universal testing machine.
- During the tension test, the grips are moved apart at a constant rate to stretch the
specimen.
- The force on the specimen and its displacement is continuously monitored and
plotted on a stress-strain curve until failure.
- The tensile strengths are calculated after the test specimen has broken. The test
sample is put back together to measure the final length, and then this measurement
is compared to the pre-test or original length to obtain elongation.
- The original cross section measurement is also compared to the final cross section
to obtain reduction in area.

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Figure 3.4: (a) Failed specimens, (b) Schematic of tensile test (Arnandha et al., 2017).
6. Bending test (Flexural Test)
Bend tests deform the test material at the midpoint causing a concave surface or a
bend to form without the occurrence of fracture and are typically performed to
determine the ductility or resistance to fracture of that material. On the other hand, the
goal of flexural test is not to load the material until failure but rather to deform the
sample into a specific shape. This test is used to determine the bending strength
(MOR) and modulus of elasticity (MOE) of the WPC products using a three point
load flat- wise bending machine. The determination of MOE and MOR is done by
using ASTM D7031 in accordance with ASTM D1037 (Arnandha et al., 2017).
- The WPC specimens for this test are shaped and cut into a shape specified in
ASTM which is in rectangular bars like in Figure 3.5a and Figure 3.5b.
- The WPC bar is placed on the 3 point bend fixture to test for bending or flexural
strength of the product sample.
- The speed of the test is must be very slow and variable depending on the support
span and depth of beam which are used in the calculation used to determine the
speed. This is because high feed rate will eventually break the sample faster.
- The test is started and ended after the sample bended about 5% off the sample or
until the sample breaks.
- The 5% deflection is determined by a calculation that takes into account the
support span and depth of beam.
- The time taken for the sample breaks and bent is recorded.
- The bend strength is recorded and will be used to comparing purposes against the
standard specification and application.

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Figure 3.5: (a) Schematic of Static Bending Test (Horizontal), (b) Schematic of Static
Bending Test (Vertical) (Arnandha et al., 2017).

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5.0 Process to Fabricate WPC
5.1 WPC Processes Considerations
Processing Considerations:
1) Pellet size
It is important that the pellet size is uniform by a more precise pellet cutting methods. When
pellets are too large, they have tendency to melt unevenly, create additional friction and settle
into a structurally inferior final product. The ideal pellet should be about the size of a small
BB bullet and rounded to achieve an ideal surface to volume ratio.
2) Moisture and temperature
To create high quality plastics with organic fillers, low moisture content is an important
consideration in any plastic production. For wood plastic composite materials, much
machinery used in the facility should be kept in dry. Organic fillers need to be dried properly
before being added to the plastics or the two is not bond correctly. The composites need to
be dried properly to avoid the onset of moulding and eventual degradation of the product.
Processing temperatures of wood plastic composites are generally processed in around 50
degrees lower than the same, unfilled material. Most wood additives will begin to burn at
around 400 degrees Fahrenheit.

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5.2 Beginning Steps in Wood Plastic Composite Fabrication
Figure 5.0 Beginning Processes of WPC Fabrication
Lumber •Logs, chips and shaving of woods
Hammermill
• Woods are crushed to powdered form
(wood flour)
Compounding
Process
• Blending of organic plant fibers
with an inorganic thermoplastic

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5.3 Manufacturing Processes of WPCs
Processes of formation of new composite from a pelletized compound made in the beginning steps:
Table 5.0 Beginning Processes of WPC Fabrication
Name of Process Diagram Justifications
Conventional
1) Extrusion 1. Single Screw Extruder
2. Co rotating Twin Screw
3. Counter Rotating Twin Screw
 Melt the polymer and mix the polymer,
wood,and additives
 Four types of extrusion:
1. Single Screw Extruder
 Material: Pre compounded fiber filled
polymer pellets
 Dryer: To dry the pellet
 Feed method: Gravity hopper
 Mixing mechanism: Barrel heat and
screw shear
 Advantages: Lowest capital
acquisition cost
 Disadvantages: High raw material
cost, lower output rate, drying system
required, polymer is melted with the

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4. WoodtruderTM
fiber with greater risk of fiber thermal
decomposition, high screw speed
with greater risk of burning at the
screw tip and inability to keep melt
temperature low with higher head
pressures
2. Co rotating Twin Screw
 Material preparation: Fiber drying
followed with high intensity blending
with the polymers and additives.
 Feed method: Crammer feeder
 Advantages: Low screw speed and
low shear mixing
 Disadvantages: A drying system is
required, size reduction system for
fed materials maybe necessary, a pre
blending is required, material
transportation can impact the mix
feed ratios
3. Counter Rotating Twin Screw
 Combination of hot melt single screw

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 Material: Wood flour or fiber at
ambient moisture content
 Feed system: Gravimetric feeders and
twin screw side feeders
 Mixing mechanism: Barrel heat,
Screw speed, screw mixing
 Advantages: The ability to process
wood at ambious moisture content
since the extruder is used to dry the
fiber with the elimination of drying
and pre blending operations and good
fiber mixing.
 Disadvantages: Need of peripheral
feeding systems, high screw speed
and no screw cooling, inability to
keep melt temperature low with
higher head pressures, and polymer is
still melted with the fiber.
4. WoodtruderTM
 Procedure: Ambient moisture content
wood flour is placed into the unit’s

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fiber feeder and dried within the twin
screw.
 Mixing mechanism: Barrel hear and
screw mixing
 Advantages: Flour and additives are
natural states and no material
preparation needed, good
polymer/fiber mixing, screw cooling,
the ability to maintain a low melt
temperature with a high head
pressure, superior venting, the
elimination of drying, size reduction
and separate pre blending equipment,
high flexible integrated process
control system, extruder unit
operations
 Disadvantages: Lower product
throughput, higher capital costs, and
using main extruder to dry is not the
most efficient manner to process dry
wood flour.

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2) Injection Molding  To produce parts containing complex geometry
and required no finishing step.
 Example: post cap for guard rail structures
3) Compression Molding/
Thermoforming (Pressing)
 The use of continuous belt presses for producing
WPC panels.

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Newer
4) Fused Layer Modelling Procedures:
1. Wood plastic composite filament is extruded through
the small orifice of heated die.
2. Initial layer placed on a foam foundation with
constant rate.
3. Extruder head follows a predetermined path from the
file.
4. After first, the table is lowered and subsequent layers
are formed.

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5) Selective Laser Sintering
(SLS)
SLS utilises powders which melt at different
temperatures and that are fused together by laser
radiation and form solids as the temperature of the
combined material decreases

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6.0 Conclusion
In a nutshell, they accommodate combination of polymer and wood flour while
encouraging ideal preparing conditions. Wood-plastic composites (WPCs) are composite
materials made of wood fiber or wood flour and thermoplastics. WPCs are true composite
materials and have properties of both materials of plastic and wood. They have stiffness and
strength between those for plastic or wood, but the density is generally higher than either.
WPCs are extremely moisture resistant, have little thickness swell in water and do not suffer
from fungal or insect attack. WPCs have good stiffness and impact resistance, dimensional
stability, resistance to rot, excellent thermal properties and low moisture absorption. WPCs
have many benefits true hybrid materials and combine the best properties of both wood and
plastics, low cost and plentiful raw materials, competitively priced and are competitive with
traditional materials, easily produced and easily fabricated using traditional wood processing
techniques, broad range of finishes and appearances and easily recycled after use. The
disadvantages of WPC are moisture sorption, high swelling, biological degradation, low
strength and stiffness and low dimensional stability. The manufacturing processes are
extrusion injection molding, compression molding or thermoforming, fused layer modelling
and selective laser sintering (SLS).