Iraqi Journal of Chemical and Petroleum Engineering 

 Vol.16 No.4 (December 2015) 59- 65 

ISSN: 1997-4884 

 
 
 
 

 

 Effect of Particle Size of Sawdust on Behaviour of Sawdust/UPE 

Composites in Water 
 

Nisreen S. Ali * and Besma M. Fahad 

Material Engineering Department, College of Engineering, University of Al-Mustansiriyah 
*Corresponding Author E-mail:nisreenalazawi@yahoo.com 

 

Abstract 

   The aim of the present work is to develop a new class of natural fillers based 

polymer composites with sawdust (S.D) which used two particle sizes (1.2 μm & 2.3 

μm) and different weight percentage from sawdust (10%, 15%, and 20%). The 

mechanical properties studied include hardness (shore D) for all samples at normal 

conditions (N.C). The unsaturated polyester (UPE) and its composites samples were 

immersed in water for  30 days to find the effect of particle size of sawdust (S.D) on 

the weight gain (Mt %) by water for all the samples, also to find the effect of water on 

their hardness. The results show that the composite materials of sawdust (S.D) fillers 

which has particle size (1.2 μm) better than (2.3 μm) particle size before & after the 

immersion in water. Also the results show a decrease in the values of the hardness for 

the UPE and its composites samples after immersion in water. The results show that 

the UPE and its composites samples have relatively increased values of weight gain 

(Mt %) by water with time of immersion, for sawdust composite samples (1.2 μm) 

particle size the samples of (15%) weight percentage have relatively highest values of 

weight gain (Mt %) by water but for samples of (2.3 μm) particle size the samples of 

(20 %) weight percentage have relatively highest values of weight gain (Mt %). 

Finally results show that the value of weight gain (Mt %) increased with increasing of 

particle size of sawdust so that the composites samples have highest value of weight 

gain (Mt %) than UPE sample. 

      
Key Words: sawdust, unsaturated polyester, hardness, absorbance of water. 

  

Introduction 

   Composite is generally defined as 

any physical combination of two or 

more dissimilar materials used to 

produce a new material which is that 

cannot be obtained by each component 

individually. Composites consist of 

one or more discontinuous phases 

embedded in continuous phase. The 

discontinuous phase is usually harder 

and stronger than the continuous phase 

and is called the reinforcement, 

reinforcing material or fillers, whereas 

the continuous phase is termed the 

matrix. The boundaries between the 

two phases are called interface. The 

properties of composites are strongly 

influenced by the properties of their 

constituent materials, their distribution 

and the interaction between them. 

Besides specifying the constituent 

materials and their properties, a 

Iraqi Journal of Chemical and 
Petroleum Engineering 

 

University of Baghdad 
College of Engineering 



 Effect of Particle Size of Sawdust on Behaviour of Sawdust/UPE Composites in Water 

60                                       IJCPE Vol.16 No.4 (Dec. 2015)             -Available online at: www.iasj.net 
 

composite material as a system is 

described by the geometry of the 

reinforcement that may be described 

by the following factors: Shape, size 

and size distribution of reinforcing 

materials. Concentration, concentration 

distribution and orientation of 

reinforcing materials [1, 2]. 
   Unsaturated Polyesters resin is a 

linear polymer with low molecule 

weight. The polyester backbone 

contains double bonds and carboxylic 

groups. In general, unsaturated 

polyester resin is prepared by the 

process of condensation 

polymerization for three basic 

components: saturated carboxylic 

acids, unsaturated carboxylic acids and 

glycols with splitting out water, and 

increasing in molecular weight by 

process called esterification. The 

general purpose of polyester is the 

product of phthalic acid, maleic acid 

and propylene glycol [3, 4, and 5]. 

   On the past decade, it was seen fast 

and steady growth of wood plastics 

industry. Among many reasons for the 

commercial success, the low cost and 

reinforcing capacity of the wood fillers 

provide new opportunities to 

manufacture composite materials. 

Although the use of wood-based fillers 

is not as popular as the use of mineral 

or inorganic fillers, wood-derived 

fillers have several advantages over 

traditional fillers and reinforcing 

materials: low density, flexibility, 

during the processing with no harm to 

the equipment, acceptable specific 

strength properties and low cost per 

volume basis. The main application 

areas of wood flour filled composites 

are the automotive and building 

industries in which they are used in 

structural applications as fencing, 

decking, outdoor furniture, window 

parts, roofline products, door panels, 

etc. The environmental awareness of 

people today is forcing the industries 

to choose natural materials as 

substitutes for non-renewable 

materials. Wood has been used as 

building and engineering material 

since early times and offers the 

advantages of not just being 

aesthetically pleasing but also 

renewable, recyclable and 

biodegradable [6, 7]. 

   Pothan et al., (1997) [8] studied the 

short banana fiber reinforced polyester 

composite concentrated on the effect of 

fiber length and fiber content. The 

maximum tensile strength was 

observed at 30 mm fiber length while 

maximum impact strength was 

observed at 40 mm fiber length. 

Incorporation of 40% untreated fibers 

provides a 20% increase in the tensile 

strength and a 34% increase in impact 

strength. 

   Mishra et al. (2003) [9] studied the 

mechanical performance of biofiber / 

glass reinforced polyester hybrid 

composites. They found that addition 

of small amount of glass fibers in the 

pineapple leaf fiber and sisal fiber 

reinforced polyester showed positive 

hybrid effect which improved the 

mechanical properties of these 

composites.  

   Lalyetal. (2003) [10] have 

investigated banana fiber reinforced 

Polyester composites and found that 

the optimum content of banana fiber is 

40%.  

   Ahmed, (2004) [11] Found that the 

composite materials were prepared 

from unsaturated polyester resin with 

different types of flakes (wood flour 

and rice husk), also a hybrid was 

prepared using the two kinds that 

mentioned above, with the almost the 

same volume fraction. Results showed 

that the composite materials of (wood 

flour) gained better mechanical 

properties compared with others, the 

hybrid gained better thermal insulation 

compared with rice husk and wood 

flour composite. 



Nisreen S. Ali and Besma M. Fahad 

 

-Available online at: www.iasj.net                    IJCPE Vol.16 No.4 (Dec. 2015)                                61 
 

   Mosadeghzad et al, (2009) [12] 

found that the Polyethylene 

therephthalate (PET) waste bottles had 

been depolymerized by glycolysis and 

reduced to its monomer and dimer. The 

glycolysed product was used to 

produce unsaturated polyester resin 

(UPR). DSC and FTIR analysis were 

conducted on the resin and the 

glycolysed product. The resin was then 

mixed with sawdust (acacia) to 

produce the sawdust/UPR composite 

based on recycled PET. The effect of 

surface treatment and filler loading on 

mechanical properties of the 

composites were studied. The results 

showed that the modulus of both 

tensile and flexural increased with 

increasing filler contents whereas the 

strength decreased. This was overcome 

by treating the sawdust fillers with 

10% sodium hydroxide (NaOH). The 

tensile, flexural, hardness and water 

absorption tests showed that the alkali 

treatment has enhanced the adhesion 

between the sawdust and the UPR 

matrix. 

   Sanaa,(2010) [13] studied the effects 

of different volumetric fractions from 

sawdust and short chopped fibers on 

the mechanical properties of 

unsaturated polyester composite then 

these results were compared with the 

properties of sawdust –fiber filled 

composites immersed for different 

periods in a salt solution of (2 N) . 

wood volume fractions {(20, 30, 50) vf 

%} selected to be added for un 

saturated polyester were studied which 

gave improvement in their selected 

studied mechanical properties for all 

reinforced composites - (only impact is 

decreased) - and particularly at higher 

values of volume fractions, were 

hardness showed an improvement by 

(15%), compressive strength gave 

obvious Improvement by (38%), while 

impact resistance decreased by (16%) 

with the reinforcement of (50 vf %) 

sawdust. The above values were 

reduced when the items were 

immersed in a salt solution for 

(60days). 

   Ahmed & Harith ,(2011)[14] studied 

The mechanical properties were 

studied including flexural strength and 

Young's modulus for composite 

materials were prepared using 

unsaturated polyester resin as binder 

with two types of fillers (sawdust and 

chopped reeds) at normal conditions 

(N.C). The Commercial wood, UPE 

and its composite samples were 

immersed in water for about 30 days to 

find the weight gain (Mt %) of water 

for the samples, also to find the effect 

of water on their flexural strength and 

Young's modulus. The results showed 

that the samples of UPE / chopped 

reeds composite gained highest values 

of flexural strength (24.5 MPa) and 

Young's modulus (5.1 GPa) as 

compared with other composites . The 

wet samples of sawdust composite 

have lowest values of weight gain (Mt 

%) of water (0.043%) as compared 

with other composites after immersion. 

Also it’s showed a slight decrease in 

values of Young's modulus and 

flexural strength except for the 

composite material formed from UPE / 

chopped reeds which showed an 

increase in the value of flexural 

strength for all the samples after 

immersion where the wet samples of 

UPE / chopped reeds composite gained 

(29 MPa) as compared with the 

samples at (N.C). 

   The objectives of this study were 

preparation of composites materials 

from natural low cost material sawdust 

(S.D) and unsaturated polyester by 

different particle size of sawdust with 

different percentage and show that 

which percentages are the best then 

studying the mechanical properties 

such as hardness of the composites 

material & absorption of the 

composites to water. 

 



 Effect of Particle Size of Sawdust on Behaviour of Sawdust/UPE Composites in Water 

62                                       IJCPE Vol.16 No.4 (Dec. 2015)             -Available online at: www.iasj.net 
 

Experimental Work 
 

1- Materials 
   Unsaturated polyester resin, (source 

china), (0.5%) of cobalt naphthenate as 

accelerator and (2%) of Methyl Ethyl 

Ketone Peroxide (MEKP) as hardener.  

   Two particles size of sawdust (S.D) 

are used (1.2μm) and (2.3μm) .these 

particles are obtained by using 

standard sieves have different sizes. 

Figure (1) shows the sawdust filler. 

 

2- Composites Preparation 
   The sawdust (S.D) filler were passed 

to heat treatment in an oven shows at 

80 
o
C for 24 h until the weight of the 

sawdust was constant. It was necessary 

to remove the residual moisture in the 

sawdust, which could greatly affect the 

mechanical properties of the 

composites [15].  

   The composites were prepared from 

unsaturated polyester resin (as a 

matrix) and added sawdust to cap by 

molding method which can be 

summarized by the following steps: 

 Determine the weight of sawdust by 
using a digital balance. 

 Weigh the weight of resin and its 
hardener and mix them carefully. 

 Mix the content thoroughly in a 
clean container by a fan type stirrer 

before casting it as sheets by using 

aluminum mold. 

 Leave the composite at room 
temperature about 24 hours to take 

time to solidify such as shown in 

figure (2). 

 

3- Mechanical Test 
   The mechanical test applied to the 

samples is hardness test by using 

(Quality test device) for polymers type 

(Sore-D). 

 

4- Water Absorption 
   The test samples of polyester resin 

and its composites were immersed in 

distilled water for (30 days), the 

immersion test was performed under 

ambient temperature. The samples 

removed from water every 72 hours 

and weighted by using digital balance. 

(Type: Sartorius, H51, made in 

Germany). The weight gain percentage 

(Mt %) was calculated by using the 

following equation [16]. 

 

Water Absorption: 

 

    (
     

  
)                    ... (1) 

 

Where (Mo) is the weight of the 

samples before soaking in water and 

(Mt) is the weight after soaking in 

water for a time period (t). 

 

Results and Discussion 
 

1- Hardness (Shore D) 
   Figure (3) shows hardness (Shore D) 

for different weight percentage of 

sawdust for UPE/sawdust composites 

from this figure it can be shown that 

the hardness of (1.2 μm) particle size 

of sawdust is higher than the hardness 

of (2.3 μm) particle size of sawdust, 

also it was showed that a drop (1.2μm) 

particle size the (15%) weight 

percentage of sawdust composites 

because of the large particle size may 

cause porosity which cause weakness 

in the composite. But for (2.3μm) 

particle size at (10%) weight 

percentage the hardness is the best. 

Figure (4) shows the relationship of 

hardness (Shore D) of the composites 

samples with weight percentage of 

sawdust after immersion in water for 

(1.2μm) and (2.3μm) particle size of 

sawdust it can be seen that the 

hardness of the samples is decreased 

after immersion of water except the 

hardness of the sample which has 

(15%) percentage of (1.2μm) particle 

size of sawdust was increased because 

the water may penetrate to the porosity 

in the specimen that cause a flotation 



Nisreen S. Ali and Besma M. Fahad 

 

-Available online at: www.iasj.net                    IJCPE Vol.16 No.4 (Dec. 2015)                                63 
 

of sawdust to the surface and make 

higher hardness and this agreement 

with Sana [13]  . Pure sample of (UPE) 

the hardness was decreased by 4.5% 

after immersion of water. Many of the 

polymers used in composites including 

UPE take some percentage of water if 

they are immersed in it for some time. 
 

2- Effect of water 
   The unsaturated polyester UPE and 

UPE/Sawdust composites samples 

were immersed in water about (30 

days) to find the effect of water on 

their weight gain. Weight gain (Mt %) 

of the samples have been calculate 

from equation (1).Figures (5) and (6) 

show the change of weight gain which 

represents by absorption percentage of 

water with time of immersion. UPE 

resin sample has absorption of water 

less than its composites samples (for 

each value of particle size of sawdust).     

   Figure (5) shows the absorption 

percentage of water with time of 

immersion for UPE/Sawdust 

composites for (1.2 μm) particle size of 

sawdust and different weight 

percentage it can be shown that 

composite which have (15%) weight of 

sawdust have been absorption of water 

higher than other weight percentage.  

   But for (2.3 μm) particle size of 

sawdust the (20 %) weight percentage 

of sawdust have been largest values of 

absorption of water which represented 

in figure (6). In addition, the 

absorption of water for composite 

samples which have (2.3 μm) particle 

size of sawdust have been higher than 

(1.2 μm) particle size of sawdust and 

this agreement with Ahmed & Harith 

[14]. 

 

 

 

 

 

 

 

 
(a) 

 
(b) 

Fig. 1, (a) 2.3μm particle size of 

sawdust. (b) 1.2μm particle size of 

sawdust. 

 

 
Fig. 2, Composite sample (UEP+S.D) 

after preparation 

 

 

 



 Effect of Particle Size of Sawdust on Behaviour of Sawdust/UPE Composites in Water 

64                                       IJCPE Vol.16 No.4 (Dec. 2015)             -Available online at: www.iasj.net 
 

 
Fig. 3, Effect of weight percentage of 

sawdust on hardness of composites 

 

 
Fig. 4, Effect of weight percentage of 

sawdust on hardness of composites 

after immersion 

 

 
Fig. 5, Effect of time immersion on 

weight gain for (1.2 μm) particle size 

composites 

 

 
Fig. 6, Effect of time immersion on 

weight gain for (2.3 μm) particle size 

composites 

 

Conclusions 
   The main conclusions of this work 

can be summarized as follows:  

1- This work shows that successful 
fabrication of natural fillers filled 

polyester composites with different 

particle size and weight percentage 

of sawdust fillers using molding 

method. 

2- The sawdust composites have 
particle size (1.2 μm) show better 

behavior in hardness (shore D) test. 

3- Adding the sawdust fillers in 
different weight percentage for two 

sizes and (15 %) weight percentage 

of sawdust of (1.2 μm) highest 

value of hardness compared with 

other percentages. 

4- The composite of (2.3 μm) the 
(10%) weight percentage of sawdust 

has highest value of hardness. 

5- The UPE and its composite samples 
have relatively increased values of 

weight gain (Mt %) after immersion 

in water. 

6- The composite samples of (2.3 μm) 
particle size have relatively highest 

value of weight gain (Mt %) of 

water than samples of (1.2 μm) 

particle size. 



Nisreen S. Ali and Besma M. Fahad 

 

-Available online at: www.iasj.net                    IJCPE Vol.16 No.4 (Dec. 2015)                                65 
 

7- The UPE and its composite samples 
have decrease in the values of the 

hardness after immersion in water. 

 

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