Journal of Biomaterials and Nanobiotechnology, 2011, 2, 435-444
doi:10.4236/jbnb.2011.24053 Published Online October 2011 (
Copyright © 2011 SciRes. JBNB
Treated Tropical Wood Sawdust-Polypropylene
Polymer Composite: Mechanical and
Morphological Study
Muhammad Abdul Mun’aim Mohd Idrus*, Sinin Hamdan, Muhammad Rezaur Rahman,
Muhammad Ssiful Islam
Department of Mechanical and Manufacturing Engineering, Faculty of Engineering, University Malaysia Sarawak, Kota Samarahan,
Email: *
Received June 4th, 2011; revised July 22nd, 2011; accepted September 27th, 2011.
In this research, composites based on treated tropical sawdust and polypropylene (PP) were prepared using hot press
molding machine. Raw sawdust was chemically treated with monomer, 2-ethylhexyl methacrylate in order to improve the
mechanical properties of the composites. The influence of the chemically treated sawdust on the physical and mechanical
properties of sawdust-PP composites were investigated at various loading level from 10 wt% up to 30 wt%. Results indicate
that the mechanical properties of the chemically treated sawdust-PP composites were found to be higher than those of the
raw ones respectively. The surface morphology obtained from scanning electron microscopy (SEM) showed that ra w saw-
dust-PP composites possess surface roughness and weak interfacial adhesion between the matrix and the filler while the
chemically treated one showed improved filler-matrix interaction. This indicates that better dispersion of the filler with the
PP matrix has occurred upon chemical treatment of the filler. Water absorption tests showed that composites prepared from
the chemically treated sawdust absorb lower amount of water compared to the ones prepared from raw sa wdust, suggesting
that hydrophilic nature of the cell ulose i n the sawdust has si gnificantly decreased upon chemical treatment.
Keywords: Wood Sawdust, Polypropylene, Mechanical Properties, Water Absorption
1. Introduction
Recently many production and application of thermo-
plastic polymer composites are being made by combin-
ing with various reinforcing fillers fiber such as sawdust/
wood flour was increased. Materials such as sawdust can
replace and reduce the utilization of plastic which relate
with the environmental issue and also offer other advan-
tage. Sawdust is obtained from natural resources and in a
large amount from wood industry as a waste. Although
the used of sawdust not very popular for WPC, but basi-
cally this material is light, cheap; stiffness and it can be
added to commodity matrix in certain loading level
hence offering one of the best solutions for the utilization
of waste wood and cheap product [1]. The uses of natural
fibers-reinforced thermoplastics are increased in recent
years such as in automotive, cosmetics, and plastics lum-
ber applications for furniture and housing. In wood in-
dustries such as timber and furniture, large amounts of
sawdust are always found as waste. Basically these saw-
dust are used as a fuel source or used to make others fur-
niture product such as plywood. Especially in Borneo
island Sarawak. There is a lot of sawdust abundantly
available from the industries.
Thus, studies on the improvement of sawdust-PP com-
posites (WPCs) have been actively followed and done
not only in industry but also in academic research field.
The sawdust used in WPC in place of the longer indi-
vidual wood fibers is most often added in particulate
form from 10 wt% up to the 50 wt% loading level by
weight. Because of the high availability and low cost of
the sawdust, it can be more useful and valuable by mix-
ing sawdust with polymer in order to improve the me-
chanical properties of the composites. In the related lit-
erature, it has been reported that most polymer compos-
ites involved fiber reinforcement, for instance from jute
fibers, bamboo fibers, oil palm empty fruits, corn fibers
and many more [2-5]. The main application area of saw-
dust filled composites is the building and automotive
industry [1,6], but they are also applied for packaging,
for the preparation of various household articles, furni-
ture, office appliances and other items [7]. However,
Treated Tropical Wood Sawdust-Polypropylene Polymer Composite: Mechanical and Morphological Study
although the use of sawdust in polymer composites has
several advantages over inorganic fillers, the hydrophilic
characteristic nature of the wood has a negative effect
and brings difficulties in obtaining good dispersion of the
wood particles and poor reinforcement between sawdust
and polymer. The sawdust is polar and polymer non po-
lar has leads to incompatibility problem between the ma-
terials. Hence affect the mechanical and physical proper-
ties of the composites [8]. Interfacial interactions are
very weak in sawdust fiber filled composites, because the
surface free energy of both the filler and the polymer is
very small [9]. The interface between the polymer matrix
and natural filler are very poor [3]. Furthermore the na-
tural fibers such as sawdust increase the water absorption
or desorption of composites when exposed to changes in
the relative humidity of the environment. Sawdust has a
better natural tendency due to a natural structure made of
cellulose fibers in an amorphous matrix of hemicellulose
and lignin. Cellulose is the main fundamental of the cell
wall of the wood, has many hydroxyl group that are
strongly hydrophilic [10]. Therefore, there is much atten-
tion has been on the run by modification or treated of the
filler by physical and chemical methods to improve the
filler-matrix interaction in order to achieved acceptable
properties. Various techniques are used or at least tried
for the improvement of interfacial adhesion including the
coupling of sawdust with functional silanes or the coat-
ing of wood flour with stearic acid and the treatment of
wood with sodium hydroxide [11-13]. Kuruvila and Sabu
have studied the effect of chemical treatments with alkali,
permanganate, isocyanate and peroxide on the tensile
properties of short sisal fiber-reinforced polyethylene
composites. They reported a considerable improvement
of the tensile properties of composites [14]. Also from
the previous research, the mechanical properties of natu-
ral fibers reinforced polymer such as Young’s Modulus
and flexural strength can be enhanced significantly by
using method pre-treating with sodium periodate and
post-treating with urotropine and urea [15].
In the present work, the raw tropical sawdust was
treated with 2-ethylhexyl methacrylate to increase the
compatibility of the tropical sawdust with the PP matrix.
Thus, the aim of this study is to manufacture composites
from raw and treated tropical sawdust and polymer PP at
different loading and subsequently characterize those
using the microstructural analysis and mechanical testing.
The effects of tropical sawdust loading on the mechani-
cal properties and morphology of the sawdust reinforced
PP composites are also reported.
2. Experimental
2.1. Materials
Wood sawdust from selected tropical softwood was used
in this investigation (Eugenia spp, Artocarpus rigidus,
Artocarpus elasticus, Koompassia malaccensis, and Xy-
lopia spp). The wood was sawn using a laboratory table
saw and the sawdust was collected. The sawdust was
then oven dried at 70˚C - 80˚C to a moisture content of
3% - 5%, then stored in polyethylene bag until needed.
The sawdust, used as reinforcing filler, was received
from external laboratory of faculty of FSTS, UNIMAS.
Polypropylene’s (PP which was used as polymer matrix,
has a melt index of 0.28 g/10 min with a density of 0.938
g/cm3. PP was supplied by Korea Petrochemical Ind. Co.,
2.2. Sample Preparation
The wood was sawn using a laboratory table saw and the
Wood sawdust was collected. The sawdust was then
oven dried at 70˚C - 80˚C to a moisture content of 3% -
5%, then stored in polyethylene bag until needed. The
particle sizes of the sawdust were in the range between
80 and 100 mesh. Chemicals used to treat sawdust were
2-ethylhexyle methacrylate supplied by merck shurchardt
OHG, Germany and sulphuric acid (H2SO4) was used as
the catalyst and its content was 5%, based on the amount
of the main chemical.
2.3. Treatment of Sawdust
Before treatment the sawdust was dried at 105˚C for
about 24 h until constant weight was reached to obtain
1% - 2% moisture content and then kept in a sealed con-
tainer. 200 mL 2-ethylhexyl methacrylate, (C12H22O2)
solution was taken in a 500 mL beaker. 500 g of sawdust
was submerged into the solution for about 1 hour at
about 70˚C in an oven. After about 1 hour, sawdust was
taken out of the beaker, washed by water and finally
dried in open air.
The monomer 2-ethylhexyl methacrylate was used for
chemical modification of wood sawdust and its main
polymer components. This chemical containing (as in
scheme 1) the functional groups of C12H22O2 monomer
was interact with the polar groups mainly hydroxyl
groups (-OH) of cellulose and lignin to form covalent or
hydrogen bonding. It is expected that, there will be re-
maining groups of hydroxyl as it is cannot be eliminate
all together because of the strong bonding. These project
main focusing is to reduce the number of hydroxyl
groups in the cellulose and lignin as the high contain
number of hydroxyl groups will lead to a weaken adhe-
sion bonding with the polymer matrix and vice versa.
2.4. Manufacturing of Wood Flour-PP Polymer
The WPC were prepared from raw and treated sawdust
and PP. The sawdust was mixed with PP in a beaker at 5
opyright © 2011 SciRes. JBNB
Treated Tropical Wood Sawdust-Polypropylene Polymer Composite: Mechanical and Morphological Study437
Scheme 1. Treatment of Cellulose in sawdust with 2-ethyl-
hexyle methacrylate.
different ratios; 10%, 15%, 20%, 25% and 30% by
weight. The mixtures were stirred continuously until
uniformly mixed without any external heating and then
pre heated in an oven for 24 hour at 80˚C to ensure the
mixing is adequate. The mixture was compression molded
into a sheet measuring 270 mm × 270 mm × 5 mm at
temperatures 200˚C ± 5˚C. Then this molding board was
cut to the test specimen size appropriate for each test. The
molding conditions were as follows; pressure, 6.8 MPa,
preheating time, 20 s; heating time, 45 min; and cooling
under a slight pressure to ambient temperature.
2.5. Micro Structural Analysis
2.5.1. Fou ri er T r ansform Infrared S pectroscopy
The infrared spectra of the raw sawdust, treated sawdust
specimens were recorded on a Shimadzu Fourier Trans-
form Infrared Spectroscopy (FTIR) 81001 Spectropho-
tometer. The transmittance range of the scan was 4000 to
400 cm–1. The obtained spectra are described in the re-
sults and discussions section.
2.5.2. Scanni ng Electron Microsc o p y
The surfaces morphology of the tropical WF-PP and in-
terfacial adhesion between the filler and the PP matrix
was examined by a scanning electron microscopy (JSM-
5510, JEOL Co. Ltd., Japan). The samples were sputter
coated with platinum and observed under the SEM. The
micrographs were taken at a magnification of 300.
2.6. Mechanical Testing
Tensile, flexural, hardness and water absorption tests
were conducted to observe the physical and mechanical
properties of the raw and treated WPC.
2.6.1. Tensile Test
The tensile tests were carried out following ASTM D
638-01 [16] using a Universal Shimadzu tensile machine
and each test was performed at a crosshead speed of 10
mm/min. For each test, five replicates samples were tested
and the average values were reported.
2.6.2. Flexur al Test
Three points bending test were conducted following
ASTM D 790-00 [17] using the same testing machine
mentioned above at same crosshead speed. The dimen-
sion of the specimen was 79 mm × 10 mm × 4.1 mm. For
each test, five replicates samples were tested and the
average values were reported. To measure modulus of
elasticity (MOE) and flexural strength, the following
equation are using;
Flexural Strength, σ = (3PL/2bd) (1)
Flexural Modulus, E = (L3m/4bd3) (2)
where P is the maximum applied load, L is the length of
support span, m is the slope of the tangent, b and d are
the width and thickness of the specimen, respectively.
2.6.3. Hardness Test
The hardness of the composites was measured using a
Rockwell Hardness Testing Machine according to ASTM
D785-98 [18]. For each test, five replicates samples were
tested and the average values were reported. Results are
shown in the following section.
2.6.4. Dimensional Stability
Raw and treated sawdust-PP samples of dimensions 40
mm × 10 mm × 4.1 mm were prepared for the measure-
ment of water absorption and thickness swelling. The
samples were air dried at 70˚C until a constant weight
was reached prior to the immersion in a static deionized
water bath. Each value obtained represented at the average
of five samples. The specimens were periodically taken
out of the water, wiped with tissue paper to removed sur-
face water, reweighed and dimensions re-measured and
immediately put back into the water. Five replicates sam-
ples for each sample were used. Water absorption were
calculated according to the formula
Water absorption (%)100%WWW 
where W2 is the specimen weight after soaking and W1 is
the weight of sample before soaking. The thickness
swelling coefficient (TS) is calculated as follows:
Thickness swelling coefficient,
100%TSTT T 
where TS is the percent of thickness swelling and T1 and T2
is the thickness of the specimen before and after the test
Copyright © 2011 SciRes. JBNB
Treated Tropical Wood Sawdust-Polypropylene Polymer Composite: Mechanical and Morphological Study
Copyright © 2011 SciRes. JBNB
3. Results and Discussion
3.1. Fourier Transform Infrared Spectroscopy
The formation of new chemical reaction cellulose com-
pound by the chemical reaction with 2-ethylhexyl metha-
crylate was confirmed by the FTIR spectroscopic analy-
sis of the untreated and treated wood sawdust, as shown
in Figure 1.
The formation of new chemical reaction cellulose
compound by the chemical reaction with 2-ethylhexyl
methacrylate was confirmed by the FTIR spectroscopic
analysis of the untreated and treated wood sawdust, as
shown in Figure 1. The FTIR spectrum of the untreated
wood sawdust clearly shows the absorption bands in the
region of 3406 cm–1, 2903 cm–1 and 1735 cm–1 due to
O-H stretching vibration, C-H stretching vibration, and
C=O stretching vibration, respectively. These absorption
bands are due to hydroxyl group in cellulose, carbonyl
group of acetyl ester in hemicellulose, and carbonyl al-
dehyde in lignin [19]. The absorption band at treated
sawdust show at O-H which shifted towards 3424 cm–1
and at C-H the absorbance shifted towards into 2916 cm–1
respectively. It can be seen that, the carbonyl peak C=O
at 1735 cm–1 was slightly shifted towards 1730 cm–1 in
the spectra of treated sawdust because the ester carbonyl
bonds in the hemicellulose was break due to the
chemical treatment. All the difference happen between
the raw and treated sawdust was confirm the chemical
treatment onto the sawdust.
A PP composite clearly shows the absorption bands of
polymer polypropylene in the FTIR spectra. In raw saw-
dust composites, the PP absorption band clearly can be
seen at region 2961 cm–1 belong to CH3 asymmetric and
symmetric stretches, 2838 cm–1 and 2918 due to CH2
asymmetric and symmetric. Another absorption bands
correspond to PP is at absorption band in the region 1377
cm-1 which is due to CH3 umbrella mode.
On the other hand, FTIR spectra of treated sawdust-PP
composites also show the existence of PP inside the com-
posites. Figure 2 clearly show the presence of the charac-
teristic of PP in the region of 2960 cm–1 and 2921 cm–1,
2838 cm–1 due to the CH3 and CH2 asymmetric and
symmetric stretches, also at the region 1377 cm–1 due to
CH3 umbrella mode. Besides that, in the treated compos-
ites there was presence a few new absorption bands
which are believed due to the chemical treatment done
before [20].
3.2. Scanning Electron Micrographs (SEM)
Morphology of the raw sawdust-PP composites and treated
sawdust-PP composites is represented in Figure 3. It has
been observed that surface morphology of treated saw-
dust-PP composites differ in smoothness and roughness
than the raw sawdust-PP composites.
Figure 3(c), (d) illustrate that the modified sawdust
was well dispersed in the composites.
Figure 1. FTIR spectra of raw and treated wood sawdust.
Treated Tropical Wood Sawdust-Polypropylene Polymer Composite: Mechanical and Morphological Study439
Figure 2. FTIR spectra of the raw sawdust-PP composites and treated sawdust-PP composites.
Figure 3. SEM Morphology of the PP reinforced with 30% raw sawdust (a)-(b) and treated sawdust (c)-(d).
This also can show that the modified sawdust compos-
ites will absorbed substantially less water after immer-
sion than raw ones. The uneven layer of lignocellulose
materials were reduces after the chemical treatment that
will lead to better mechanical properties.
3.3. Mechanical and Physical Properties of
The flexural and tensile properties were explained in this
Copyright © 2011 SciRes. JBNB
Treated Tropical Wood Sawdust-Polypropylene Polymer Composite: Mechanical and Morphological Study
3.3.1. Flexural Properties
Flexural strength and modulus of raw and treated saw-
dust composites at different filler loading are shown in
Figures 4 and 5 respectively. The result showed that the
flexural strength increased with increased in filler load-
ing [15]. All the treated sawdust composites showed
higher flexural strength than the raw sawdust composites.
Furthermore, from Figure 5, the flexural modulus is in-
creased with filler loading increased which is in agree-
ment with the other researcher [15,21,22]. It is found that
the flexural strength decreased approximately 1.6% re-
spectively over the raw sawdust-PP composites at 10
wt% filler loading, while for the 15 wt% - 25 wt% filler
loading, the flexural strength gradually increase approxi-
mately from 6.6% - 10.8% respectively. However at 30
wt% raw sawdust-PP composite the flexural strength
slightly decreased approximately 1.6% than the 25 wt%
filler loading. This showed that, with the small incorpo-
ration of small amount of wood sawdust, at 10 wt%.
filler loading , the flexural strength of the composite was
lowest than the raw PP. When the sawdust loadings in-
creased, the flexural strength gradually increased which
is due to the increased in resistance to shearing in the
Figure 4. Flexural properties of composites at different
filler loadings.
Figure 5. Flexural modulus of raw and treated sawdust/PP
composites at different filler loading.
composites structure probably because the presence of
the fibers. Meanwhile in the treated sawdust-PP compo-
sites the increment was 2.3% - 16.6% at filler loading
from 10 wt% up to 25 wt%. After that at 30 wt% treated
sawdust, the flexural strength showed slightly decreased
about 1.57%.
The adding of both raw and treated sawdust has sig-
nificantly increased both flexural strength and modulus
of the composites. Since wood fibers have high modulus
properties, hence higher fiber concentration required higher
stress for the same deformation. The increased in filler-
matrix adhesion was increased the stress transfer from
the matrix to the filler. Meaning that, increased in the
flexural modulus will attribute to the better incorporation
of rigid sawdust into matrix polymer PP.
3.3.2. Tensile Strength
The properties of tensile strength and Young’s modulus
of both raw and treated sawdust-PP composites at dif-
ferent filler loading are shown in Figures 6 and 7. From
Figure 6, the tensile strength for raw and treated sawdust
gradually decreased with an increase in filler loading
from 10 wt% - 30 wt% [15]. The tensile strength de-
creased due to the increasing filler content in the com-
posites was effected the interfacial strength become weak
between the filler and matrix [15,21.23]. But the treated
sawdust showed slightly higher than raw one at all filler
loading. Indicating that, the chemical treatment had im-
proved the tensile strength of the composites. The saw-
dust was treated with with 2-ethylehexyl methacrylate in
order to improve the mechanical properties of the com-
posites. The weak interfacial adhesion between the hy-
drophilic sawdust and hydrophobic PP matrix and high
water absorption is caused by the hydroxyl group in the
raw sawdust. Basically there are three hydroxyl groups
present in the cellulose anhydroglucose unit. One is pri-
mary hydroxyl group at C6 and the other two secondary
hydroxyl groups at C2 and C3. In this research, the
2-ethylhexyl methacrylate breaks the hydroxyl groups at
C2 positions during the reaction. This convert the OH
groups at C2 become C11H18O2 as illustrated in Scheme 1.
The FTIR spectroscopic analysis confirmed this phe-
nomenon occurs in Figure 2. Furthermore, the interfacial
bonding between sawdust and the PP matrix significantly
improved in the composites due to the replacement of the
hydroxyl groups at C2 in the treated sawdust even the
value is lower compare with the net PP [15,24].
Figure 7 shows the variation of the Young’s modulus
at different fiber loading. The Young’s modulus show
increased with fiber loading from 10 wt% - 30 wt% is in
agreement with other researcher [15,24]. It is expected
because the incorporation of rigid sawdust into the soft
thermoplastics was occurred. Treated sawdust-PP com-
posites exhibit higher values of Young’s modulus than
opyright © 2011 SciRes. JBNB
Treated Tropical Wood Sawdust-Polypropylene Polymer Composite: Mechanical and Morphological Study441
Figure 6. Tensile strength of PP composites of raw and
treated sawdust at different filler loading.
Figure 7. Variation of the Young’s modulus of sawdust-PP
composites at different filler loading.
raw composites. According to another researcher who
obtained the same result reported that crystallites possess
higher modulus compare those of amorphous substances
[5,8]. The higher value of Young’s modulus was achieved
by treated sawdust at 30 wt% filler loading at 1.25 GPa,
however raw sawdust were at 1.1 GPa.
During chemical treatment with the monomer, the
sawdust surface probably attains somewhat crystalline
nature, which might be dominated over its bulk nature,
thus give higher modulus of the treated sawdust-PP com-
posites. Meanwhile, the matrix mobility were decreased
due to the incorporation of rigid fiber into the soft matrix
hence make the composites more stiffness. These conse-
quently increase the tensile strength of the treated saw-
dust at different filler loading such as 2.7%, 4.5%, 4.9%,
4.6% and 7% increased at 10, 15, 20, 25 and 30 wt%
respectively compare to raw one.
3.3.3. Hardness Test
Figure 8 shows the average values of hardness of the
composites at various sawdust filler loading. “Hardness”
is a general term which describes a combination of pro-
Figure 8. Variation of hardness of the raw and treated saw-
dust-PP composites at different filler loading.
perties, such as the resistance to surface indentation,
abrasion, and scratching. In this study, hardness was a
measure of resistance to indentation and the values ob-
tained were used to evaluate the mechanical strength of
each composite.
The hardness both raw and treated sawdust-PP com-
posites increased with an increased in the fiber loading.
It is observed that the treated sawdust exhibited better
hardness compared to raw ones at all filler loading from
10 wt% - 30 wt% [24]. Further, there was considerable
improvement in the hardness for the treated sawdust-PP
composites. This phenomenon could be attributed to the
better adhesion of the polymer to the sawdust fibre
brought about by the chemical treatment [25]. The high-
est is observed at 30 wt% filler loading for both raw and
treated which is at 80.2 and 90.2 Rockwell. This could be
attributed because the good dispersion formed between
the matrix and the filler beside the reducing of voids and
stronger interfacial bonding between the fiber and matrix.
The decreased of flexibility and increase of stiffness of
the respective composites enhance the hardness proper-
ties as reported by other researcher [15].
3.3.4. Water Ab s orption
Figure 9 shows the water absorption characteristic for
the raw and treated sawdust-PP composites against filler
The water absorption (wt%) for the raw and treated
sawdust composites, were varies depending on the filler
loading. From the observation, the water absorption of
composites increased gradually with an increase in filler
loading [15,19,23]. This is due to the higher contents of
filler loading in the composites that can absorb more
water. When the content of wood sawdust increase in the
composite, the number of free -OH groups is contain
more from the cellulose and hemicellulose inside the
fiber responsible for increase the water absorption. These
free -OH or hydroxyl groups come in contact with water
and form hydrogen bonding, which result in weight gain
in the composites. In contrast, the treated sawdust-PP
Copyright © 2011 SciRes. JBNB
Treated Tropical Wood Sawdust-Polypropylene Polymer Composite: Mechanical and Morphological Study
Figure 9. Variation of Water absorption of the raw and
treated sawdust-PP composites at different filler loading
after 16 days in 24 Hr soaking in water.
composites exhibits the lowest water absorption compare
to raw one at all filler loading. This implies that the che-
mical treatment had removed some -OH groups inside
the cellulose thus reduces the number of free -OH groups
inside the composites resulted in lower availability or the
hydrophilic characteristic to absorb water for all the
treated composites.
Meaning that, the fewer free hydroxyl groups in
treated sawdust-PP composites attributed to the lower
water absorption. From the result, neat PP showed the
lowest water absorption followed by composites with
10% wt. filler loading up to 30 wt% filler loading. Com-
posite with high filler contents (30 wt%) exhibit highest
water absorption for both raw and treated saw- dust-PP
composites due to increase number of micro voids on the
surface which is caused by the bigger amount of poor
bonded area between the hydrophilic sawdust and hy-
drophobic matrix polymer which also refer to the de-
crease in density of the composites from Table 1. Thus
water is easily entered through these voids [2]. Another
reason of less water content of the treated sawdust com-
posites is good interaction between the matrix and
treated sawdust that resulted in void minimization in the
resultant composites [24].
3.3.5. Thickness Swelling Test
The result of thickness swelling (TS) test was shown in
Table 1. However in Figures 10 and 11 shows the thick-
ness swelling behaviour of the composites. The TS of
composites was mainly exposure of the sawdust fiber on
the surface of the composites. TS of the composites were
carried out for several hours until a constant weight was
obtain. In this study, thickness swelling of composites
was carried out for 24 hour in about 16 days. It was ob-
served that the TS for all composites increase as the filler
loading (sawdust content) increased inside the compos-
ites. The result showed that the thickness swelling was
the highest for the 30 wt% raw sawdust-PP (0.69%),
which corresponded to the highest water absorption (Ta-
ble 1 and Figure 9). In a similar manner to the water
absorption, the thickness swelling increased with sawdust
Table 1. Data for physical properties of the composites.
absorption (%)
swelling (%)
wt. % Raw TreatedRaw Treated RawTreated
PP only0.841 0.841 -
10 0.8860.8941.972 1.701 0.2150.17
15 0.9130.9242.403 2.104 0.350.28
20 0.9160.9363.057 2.704 0.430.33
25 0.9380.9523.267 2.983 0.5650.435
30 0.9460.9613.752 3.638 0.690.56
Figure 10. Thickness swelling versus water immersion time
for raw wood-flour-PP com p osites.
Figure 11. Thicknesses swelling versus water immersion
time for treated wood-flour-PP composite.
opyright © 2011 SciRes. JBNB
Treated Tropical Wood Sawdust-Polypropylene Polymer Composite: Mechanical and Morphological Study443
content for both raw and treated sawdust-PP composites.
Table 1 showed all treated sawdust-PP composite exhibit
lower thickness swelling than the raw one. At 10, 15, 20,
25 and 30 wt% sawdust, the thickness swelling gradually
decrease after chemical treatment from 0.215% to 0.17%,
from 0.35% to 0.28%, from 0.43% to 0.33%, from
0.565% to 0.435% and from 0.69% to 0.56% respec-
This indicates that the raw composites possess high
porosity or the presence of void on the surface of raw
composites. This is responsible for the changes in dimen-
sion of cellulose-based composites, particularly in the
thickness, and the linear expansion due to reversible and
irreversible swelling of the composites [26]. Meanwhile
in contras the pure PP show the lowest TS (%) which is
0%. In other words there were no TS in the PP compo-
sites due to nature of PP as water resistant. It was also
indicated that, TS values of composite increase with an
increase of water absorption time. When the composites
exposed to the water immersion time increased, a sig-
nificant amount of water absorbed, resulting in the swell-
ing of the fiber. Hence the swelling of the fiber gives
stress on the surrounding.
3.3.6. Density of Composite
It is observed from the Table 1, density of sawdust-PP
composites for raw and treated was increased as the saw-
dust wt% loading increased. The highest was at treated
sawdust 30 wt% which is 0.961 g/cm3 respectively com-
pare to raw one, 0.946 g/cm3.
It is observed that, all raw sawdust-PP composites
have lower density compare to raw as the fiber increase.
This shows that there was present of voids inside the raw
composites. After the chemical treatment, better interac-
tion between the matrix and the fiber were exist hence
had resulted in void minimization in the composites. As
the fiber increase, the number of voids increases as more
fiber and matrix leak out during the curing step thus cre-
ate void inside the composites.
4. Conclusions
In this work, raw sawdust was chemically treated with
2-ethylhexyl methacrylate in order to remove some
amount of hydroxyl groups in cellulose and improved the
adhesion between the matrix and fiber. It is observed that
the tensile strength of the composites of raw and treated
sawdust is decrease with increasing filler loading. The
values of the Young’s modulus, flexural strength, flex-
ural modulus, and hardness are found to increase with an
increase in filler loading and the values are found to be
higher for treated sawdust-PP composites than the raw
ones. Hence, meaning that treated sawdust attributed to
better dispersion of the filler in the matrix and stronger
filler-matrix interfacial adhesion. The difference in the
filler-matrix interfacial adhesion between the filler and
the matrix for raw and treated sawdust reinforced com-
posites is clearly seen in the SEM micrographs. The im-
proved mechanical properties of the treated sawdust-PP
composites are supported by SEM images that show bet-
ter filler-matrix adhesion compared to raw ones. Water
absorption increased with filler loading however, treated
sawdust-PP composites showed the lowest water absorp-
tion and thickness swelling compared to raw composites,
showing that the chemical treatment of sawdust has con-
siderably reduced the hydrophilic nature of the sawdust.
5. Acknowledgements
The authors would like to thank the University Malaysia
Sarawak (UNIMAS) for providing the sponsorship under
FRGS research grant (UNIMAS/ FGRS/02(20)/741/2010
[27] that has made this work possible.
[1] A. K. Bledzki and J. Gassan, “Composites Reinforced
with Cellulose Based Fibres,” Progress in Polymer Sci-
ence, Vol. 24, No. 2, 1999, pp. 221-274.
[2] H. S. Yang, H. J. Kim, H. J. Park, B. J. Lee and T. S.
Hwang, “Water Absorption Behavior and Mechanical
Properties of Lignocellulosic Filler–Polyolefin Bio-Com-
posites,” Composite Structures, Vol. 72, No. 4, 2006, pp.
[3] I. Ahmad and T. M. Mei, “Mechanical and Morphologi-
cal Studies of Rubber Wood Sawdust-Filled UPR Com-
posite Based on Recycled PET,” Journal of Poly-
mer-Plastics Technology and Engineering, Vol. 48, No.
12, 2009, pp. 1262- 1268.
[4] A. K. Rana, A. Mandal, and S. Bandyopadhyay, “Short
Jute Fiber Reinforced Polypropylene Composites: Effect
of Compatibiliser, Impact Modifier and Fiber Loading,”
Composites Science and Technology, Vol. 63, No. 6,
2003, pp. 801-806. doi:10.1016/S0266-3538(02)00267-1
[5] A. R. Sanadi, D. F. Caulfield, R. E. Jacobson and R. M.
Rowell, “Renewable Agricultural Fibers as Reinforcing
Fillers in Plastics: Mechanical Properties,” Industrial &
Engineering Chemistry Research, Vol. 34, No. 5, 1995,
pp. 1889-1896. doi:10.1021/ie00044a041
[6] A. K. Bledzki, O. Faruk and V. E. Sperber, “Cars from
Bio-Fibres,” Macromolecular Materials and Engineering,
Vol. 291, No. 5, 2006, pp. 449-457.
[7] A. K. Bledzki, M. Letman, A. Viksne and L. Rence, “A
Comparison of Compounding Processes and Wood Type
for Wood Fibre-PP Composites,” Composites A, Vol. 36,
No. 6, 2005, pp. 789-797.
[8] A. Karmakar, S. S. Chauhan, J. M. Modak and M.
Copyright © 2011 SciRes. JBNB
Treated Tropical Wood Sawdust-Polypropylene Polymer Composite: Mechanical and Morphological Study
Copyright © 2011 SciRes. JBNB
Chanda, “Mechanical Properties of Wood-Fiber Rein-
forced Polypropylene Composites,” Composites A, Vol.
38, No. 2, 2007, pp. 227-233.
[9] D. Maldas and B. V. Kokta, “Interfacial Adhesion of
Lignocellulosic Materials in Polymer Composites: An
Overview,” Composite Interfaces, Vol. 1, No. 1, 1993, pp.
87-108. doi:10.1163/156855493X00338
[10] N. E. Marcovich, M. M. Reboredo and M. I. Aranguren,
“Dependence of the Mechanical Properties of Wood
Flour-Polymer Composites on the Moisture Content,”
Applied Polymer Science, Vol. 68, 1998, pp. 2069-2076.
[11] M. D. H. Beg and K. L. Pickering, “Fiber Pre-Treatment
and Its Effects on Wood Fiber Reinforced Polypropylene
Composites,” Materials and Manufacturing Processes,
Vol. 21, No. 3, 2006, pp. 303-307.
[12] M. N. Ichazo, C. Albano, J. Gonzalez, R. Perera and M.
V. Candal, “Polypropylene/Wood Flour Composites:
Treatments and Properties,” Composites Structure, Vol.
54, No. 2, 2001, pp. 207-214.
[13] N. M. Stark, “Wood Fiber Derived from Scrap Pallets
Used in Polypropylene Composites,” Forest Products
Journal, Vol. 49, No. 6, 1999, pp. 39-46.
[14] J. Kuruvilla and T. Sabu, “Effect of Chemical Treatment
on the Tensile Properties of Short Sisal Fibre-Reinforced
Polyethylene Composites,” Polymer, Vol. 37, No. 23,
1996, pp. 5139-5149.
[15] Md. Rezaur Rahman, Md. Nazrul Islam, Md. Monimul
Huque, “Influence of Fiber Treatment on the Mechanical
and Morphological Properties of Sawdust Reinforced
Polypropylene Composites,” Composites: Part A, Vol. 18,
No. 3, 2010, pp. 1739-1747.
[16] ASTM Standard D 638-01, “Test Methods for Tensile
Properties of Plastics,” In: Annual Book of ASTM Stan-
dard, Ed., American Society of Testing and Materials,
Vol. 8, No. 1, 2002, pp. 45-57.
[17] ASTM Standard D 790, “Test for Flexural Properties of
Unreinforced and Reinforced Plastics and Electrical In-
sulating Materials,” 2000.
[18] ASTM Standard D 785-98, “Test Method for Rockwell
Hardness of Plastic and Electrical Insulating Materials,”
In: Annual Book of ASTM Standard, Ed., 2002.
[19] H. Ismail, M. Edyhan, and B. Wirjosentono, “Bamboo
Fiber Filled Natural Rubbercomposites; The Effects of
Filler Loading and Bonding Agent,” Journal of polymer
Testing, Vol. 21, 2002, pp. 139-144.
[20] B. Smith, “Infrared Spectra of Polymers: Polypropylene,”
B. Smith, “Infrared Spectral Interpretation: A Systematic
Approach,” CRC Press, New York, 1999.
[21] C. W. Lou, C. W. Lin, C. H. Lei, K. H. Su, C. H. Hsu, Z.
H. Liu and J. H. Lin, “PET/PP Blend with Bamboo Char-
coal to Produce Functional Composites,” Journal of Ma-
terials Processing Technology, Vol. 192-193, 2007, pp.
428-433. doi:10.1016/j.jmatprotec.2007.04.018
[22] S. Joseph, M. S. Sreekala, Z. Oommen, P. Koshy and S.
A. Thomas, “Comparison of Mechanical Properties of
Phenol Formaldehyde Composites Reinforced with Ba-
nana Fibers and Glass Fiber,” Composites Science and
Technology, Vol. 62, No. 14, 2002, pp. 1857-1868.
[23] H. S. Lee, D. Cho and S. O. Han. “Effect of Natural Fiber
Surface Treatments on the Interfacial and Mechanical
Properties of Henequen/Polypropylene Biocomposites,”
Macromolecular Research, Vol. 16, No. 5, 2008, pp. 411-
417. doi:10.1007/BF03218538
[24] M. R. Rahman, M. M. Huque, M. N. Islam and M. Hasan,
“Improvement of Physico-Mechanical Properties of Jute
Fiber Reinforced Polypropylene Composites Bu post-
Treatment,” Composites: Part A, Vol. 39, No. 11, 2008,
pp. 1739-1747. doi:10.1016/j.compositesa.2008.08.002
[25] S. B. Elvy, G. R. Dennis and N. Loo-Teck, “Effects of
Coupling Agent on the Physical Properties of Wood-
Polymer Composites,” Journal of Materials Processing
Technology, Vol. 48, No. 1-4, 1995, pp. 365-372.
[26] H. P. S. Khalil-Abdul, A. M. Issam, M. T. Ahmad-Shakri,
R. Suriani and A.Y. Awang, “Conventional Agro-compo-
sites from Chemically Modified Fibres,” Industrial Crops
and Products, Vol. 26, No. 3, 2007, pp. 315-323.
[27] G. E. Myers, “Wood Flour and Polypropylene or High
Density Polyethylene Composites: Influence of Maleated
Polypropylene Concentration and Extrusion Temperature
on Properties,” International Journal of Polymeric Mate-
rials, Vol. 15, 1999, pp. 171-186.