Malaysian Polymer Journal, Vol. 7 No. 2, p 46-55, 2012 Available online at www.cheme.utm.my/mpj

CURING BEHAVIOUR AND TENSILE PROPERTIES OF UNSATURATED POLYESTER CONTAINING VARIOUS STYRENE CONCENTRATIONS

Osman E. A.,1 Vakhguelt, A.,2 Sbarski; I.,3 Mutasher, S. A.,4*

1School of Engineering Computing and Sciences Swinburne University of Technology (Sarawak Campus) Jalan Simpang Tiga, 93350, Kuching, Sarawak, Malaysia

2Faculty of Engineering, Nazarbayev University, 53 Kabanbay batyr ave. postal codes 010008, Astana, Republic of Kazakhstan,

3Faculty of Engineering and Industrial Sciences, Swinburne University of Technology, PO Box 218 HAWTHORN VIC 3122, Australia

4Ministry of Higher Education, College of Applied Sciences- Engineering Department Postal Code: 311, P. O. Box 135 Sohar, Sultanate of Oman

Corresponding author e-mail: saadassi@gmail.com & saadj.soh@cas.edu.om

Abstract: In this paper the curing behaviour of unsaturated polyester containing different concentration of styrene monomer has been investigated via measuring viscosity, gel time, and maximum exotherm temperature. In addition the effect of styrene concentrations on the tensile and modulus properties of unsaturated polyester is studied. The MEKP with different concentrations was used as initiator for curing the unsaturated polyester and DMA curing accelerator with different ratios started with 0.1, 0.2 and 0.3. The effect of varying the level of water content on the exotherm behaviour was investigated. The results show that the water affects the action of initiator and accelerator system. The results also show that the density and viscosity of unsaturated polyester decline with the increase of styrene concentration. The viscosity is 219.3 cP at 26 ºC for the (60%up-40%st), 98.4 cP at 26 ºC for the (50%up-50%st), and 39 cP at 26 ºC for the (40%up-60%st). The increasing styrene concentration for certain concentration of MEKP decreases the maximum tensile strength and tensile modulus. Besides, variation of MEKP and DMA ratio does not have any significant effect on the mechanical properties of the material such as, maximum strength and tensile modulus. Maximum strength and tensile modulus have the same trend for various concentration ratios of styrene.

Keywords: Unsaturated Polyester, Thermoset Properties, Curing Behaviour, Gel Time, Exotherm Temperature, Styrene Concentration

1. INTRODUCTION

Unsaturated polyester resins are one of the most important thermoset material used in composites industry for the preparation of molding compounds, laminates, coatings, and adhesives as having low cost and good mechanical properties [1, 2]. Thermoset resin is defined as a plastic material which is initially a liquid monomer or oligomers or a pre-polymer, which is cured by either application of heat or catalyst to become an infusible and insoluble material [3]. Unsaturated polyester resins are viscous liquids consisting of oligomeric unsaturated polyester and polymerizable diluents (e.g. styrene or acrylate/methacrylates), as well as polymerization inhibitors. In fact they can be cured to give insoluble, infusible solid plastics through a free radical curing process [4]. Carlton Ellis found that unsaturated polyester could be mixed with styrene, and copolymerised into a rigid polymer. The crosslinking reaction between unsaturated polyester resin and styrene allows one polymer chain to connect with other polymer chains and to produce a three dimensional

networks, which convert the resin system from a viscous liquid into hard, thermoset solid [5, 6]. Styrene acts both as a crosslinking agent and as a viscosity reducer so that the resin can be processed. The resulting material becomes solid with dramatic increase in mechanical properties and even with the physical and chemical properties [7]. In conventional unsaturated polyester the styrene content varies between (38 and 45) wt% [8]. A number of studies have qualitatively correlated the effect of initiator(s) and accelerator on the gel time, cure rate and exotherm behaviour of unsaturated polyester resins. The curing reaction is a very complicated process that is affected by many different things, such as weather, humidity, resin uniformity, conditions of ingredients as they are stored, suppliers, equipment conditions, etc. [9]. The curing behaviour of an unsaturated polyester resin was studied by gel time and pseudo-adiabatic exotherm measurements by Cook, et al, [10]. They concluded that an increase in the concentrations of initiator (either methyl ethyl ketone peroxide or acetyl acetone peroxide) or cobalt octoate accelerator decreased the gel time in a reciprocal fashion and increased the rate

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of polymerization. A various combinations of low- and high-decomposition temperature initiators and dual promoters were used to cure an unsaturated polyester resin. Methyl ethyl ketone peroxide (MEKP) and acetyl acetone peroxide (AAP) solutions were used as low-temperature initiators. Benzoyl peroxide (BPO) and t-butyl perbenzoate (TBPB) were used as medium and high-temperature decomposition initiators, respectively [11]. The dual initiator effect on exotherm reaction have been reported by Atta et al [12] and the overall results shows that the dual initiator or a dual promoter can avoid short time exothermic reactions. The compressive properties and the curing behaviour of the unsaturated polyester resins in the presence of Vinyl Ester resin were investigated by Cook [13] his results shows that increasing the cure temperature and the vinyl ester content led to a pronounced improvement in the compression strength and Young’s modulus. There are some additives that make the curing reaction go slower such as, inhibitors, styrene, filler, oxygen, flame retardants, reinforcements, and mold heat capacity. Mechanical properties of unsaturated polyester with polyvinyl acetate (PVAc) as a curing agent were studied by Hayaty and Beheshty [14]. They found that the mechanical properties of cured resin decrease with the increasing (PVAc). The unsaturated polyester properties were dependent on styrene content including the thermal stability and mechanical properties of the unsaturated polyester reflect the extension of phase segregation as the results explained by Sanchez, et al. [15]. The effect of nanofillers on the properties of unsaturated polyester had been also investigated by Pereiram et al. [16], the results show that incorporation of nanofillers in the resin reduces the flexural strength of polyester resin while the flexural modulus remains unchanged. In addition, there is a significant reduction in the UP flammability by incorporation of these nanofillers. Gel time and peak exothermal temperatures were studied in term of wt% of MEKP, accelerator, filler and glass fibers [17]. They found that the gel time increased with amount of filler and glass fiber while decreased with amount of catalyst as well as accelerator. This paper investigates the rheological properties of the unsaturated polyester containing different concentrations of styrene via measuring viscosity, gel time, maximum exotherm temperature and mechanical properties. In addition, the paper discusses the curing reaction process of unsaturated polyester by adding different weight fraction of kenaf fiber. This is a very important stage in processing of unsaturated polyester resin for producing a composite product of high quality.

2. MATERIALS AND EXPERIMENTS

2.1 Unsaturated Polyester

Unsaturated polyester up (60%up + 40%st), and styrene st with density (0.909) g/cm3 was obtained from BORNEO INDAH SDN BHD with the properties such as appearance (pink), density (1.12) g/cm3, and stability in the dark below 25ºC. The unsaturated polyester contains 50% styrene was prepared by adding 20g of styrene to 100g from unsaturated polyester (60%up + 40%st).

2.2 Curing Agents

Methyl ethyl ketone Peroxide (MEKP) and Dimethyl Aniline (DMA) were obtained from the same supplier for unsaturated polyester resin and used as a catalyst and accelerator, respectively. The properties of DMA were as follows: the density at (20-24) ºC temperature - (0.955-0.960) g/cm3, molecular weight - 121.18 g/mol, and the chemical symbols - C8H11N.

2.3 Differential Scanning Calorimeter (DSC)

The differential scanning calorimeter was carried out in a TA Instruments DSC 2960, which calculates the heat flow to and from the specimen with respect to the temperature and time, sample weight of (5-10) mg at heating rate of 10 ºC/min. There is a reference material introduced in this method to compare the rate of heat exchange irrespective of whether it’s an endothermic or exothermic such as melting, crystallization and curing with respect to temperature. Change in heat capacity is also detected using this test. The testing temperature is usually rated between atmospheric temperatures to 1500oC.

2.4 Mould Design and Fabrication

Specimens have been prepared for three different styrene content namely (60%up + 40%st), (50%up + 50%st) and (40%up + 60%st).The MEKP was added (1, 2, 3 and 4)% by volume of 100 ml of up resin, mixing manual for 3 min and laid up in the mould for 24 hrs. The mould should be well cleaned and dry, for this reason, a release agent (wax) is laid up on the mould before powering mixture. The same process is applied to prepare the resin specimens with fixed MEKP concentration of 1% and change the DMA volume fraction stared from 0.1%, 0.2% and 0.3% by volume of unsaturated polyester UP resin. Figure 1 shows the mould of tensile specimens of the matrix. The mould consists of three parts, the base part and the upper part made form aluminium while the intermediate gasket made from Teflon.

Figure 1: Tensile specimens mold

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3. RESULTS AND DISCUSSIONS

3.1 Viscosity Measurement

LVDV-II+Pro Viscometer Brookfield were used to measure the viscosity of the unsaturated polyester for different styrene concentrations at different temperatures. A standard Griffin beaker with 600 ml was used in the test. The experiments are start at 26 ºC and raise until 50 ºC. Figure 2 illustrated the distribution of the viscosity with temperature. As expected with increasing temperature the viscosity drops significantly. It has been observed that the viscosity decreases with increase in styrene concentration ratio, the results shows that the viscosity was 219.3 cP at 26 ºC and 64.5cP at 50 ºC and the percentage decreasing was 29.48 % for the first ratio of (60%up +40%st), while the percentage decreasing for the ratio of (50%up +50%st) is 64.93%, and for the last styrene ratio of (40%up +60%st) is 61.79%.

Figure 2: Viscosity change with temperature unsaturated polyester containing different concentrations of styrene

3.2 Density Measurement

The styrene ratio controls the reactivity of the unsaturated polyester and also the crosslinking density of the final network. The styrene ratio controls the reactivity of the unsaturated polyester and also the crosslinking density of the final network. Figure 3 explain the density variations with the increase in styrene concentration at 26 ºC. It is clear that the density of the matrix is decreasing while the styrene ratio was increased.

3.3 Cure Characteristics

3.3.1 Curing Time and Peak Exotherm Temperature

The cross-linking reaction is a very important stage in the processing of unsaturated polyester into a composite product, also does the exotherm temperature of cure after the completion of the

processing. The crosslinking reaction is a highly exothermic reaction, and the temperature can increase up to 100-200 ºC. Figure 4 explains clearly the exotherm temperatures for three different styrene ratios of unsaturated polyester. The maximum exotherm temperature was about 156 ºC for the ratio 50% of styrene followed 60% at about 132.9 ºC and 40% at about 128 ºC.

Figure 3: Density change with styrene concentration ratio for unsaturated polyester resin

Figure 4: Curing time for different volume fraction of unsaturated polyester with 1% MEKP

Figure 5 presents the gel time for different ratios of unsaturated polyester containing different concentrations of MEKP. 40% st was cure faster than both 50%st and 60%st. This increasing in gel time is a clear indication of increasing styrene content, which is mean that the styrene works as dilution agent for a certain value of MEKP.

Figure 6 presents the time-to-peak for different ratios of unsaturated polyester containing different concentrations of MEKP. It is clearly observed that the

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time-to-peak shows a similar behaviour with respect to the MEKP concentration ratio. One can observe the time-to-peak significantly changes when the styrene concentration increases. The second effect of styrene is its ability to act as a crosslinking agent. Therefore the styrene makes the crosslinking to occur more quickly and readily. This means the styrene speed up the reaction process, although this effect is usually observed later in the overall curing cycle. Therefore the time-to-peak decreases when the styrene concentration ratio increases. Generally increasing the MEKP concentration decreases the time to peak.

Figure 5: Gel time for unsaturated polyester containing different concentrations of styrene and MEKP ratios

Styrene work as a crosslinking agent, the free radical can react with the styrene to form a bridge to another polyester chain. In forming this bridge, a free radical is created on the second polyester molecule. Heat was evolved with each bond that is formed. From Figure 7 we also notice that 40%st produces a lower exotherm temperature than both 50%st and 60%st. This lower exotherm could potentially make it easier in handling when making the composites and also possibly reduce the shrinkage of the material [4].

DMA as accelerator effects the gel time, time to peak and the exotherm temperature for unsaturated polyester with different styrene concentrations. The increasing in DMA ratio decreases both, the gel time and time to peak. In addition, the increasing of DMA concentration increases the exotherm temperatures only for the first addition ratio of DMA (0.1vol %), while the increasing was very small for the ratio of (0.2, 0.3vol %) for the same styrene concentration ratio. The exotherm temperatures increase for different styrene concentrations are obviously shown in Table 1. The test results are very important for providing information about the gel time variation during the preparation of the composites product.

Figure 6: Time to peak for unsaturated polyester containing different concentrations of styrene and MEKP

Figure 7: Exotherm temperatures for unsaturated polyester containing different concentrations of styrene and MEKP

3.3.2 DSC Results for Different Styrene Concentrations

The output of a DSC measurement is a plot of the difference of heat delivered to the sample and to the reference as a function of the sample temperature for (60%up-40%st) unsaturated polyester resin with 1%MEKP as shown in Figure 8.. Table 2 explain the significant changes in Tg of unsaturated polyester for different styrene concentrations with different MEKP and DMA concentration ratios. In the first ratio of styrene 40% there insignificant changes with increasing MEKP, while Tg decreases with adding 0.1vol% DMA then started to increases with the increasing of DMA. While for the second ratio of styrene the maximum transition temperature is at 2vol% of MEKP and after that stared to decrease with increasing of MEKP. The glass transition temperature has the same trend for DMA and the maximum is at 0.2 vol%. It is evident that Tg measured by DSC increases as the MEKP level increases for certain level and then decreases. Similar results have been reported by Ross et al. [18].

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Figure 8: Example of thermogram curve for DSC Measurement, (60%UP-40%ST) unsaturated polyester resin with 1%MEKP

3.3.3 Effect of Reinforcement on Curing Process

The polyester resin containing different ratios of styrene were mixed at different concentrations of MEKP at 26 ºC for 1 min and then mixture was poured into a paper cup (9.5cm diameter and 9cm deep) and weighted using weight scale. With the weight of approximately 112.7 g it was added with 10% wt kenaf fiber size 1mm. The temperature data was measured by placing a thermocouple covered by aluminium foil at the centre of isolated paper cup connected to a digital thermometer. Stop watch was used to measure the gel time. Table 3 clearly explains that the fiber inert to the crosslinking reactions for one volume fraction of MEKP as an initiator and for the unsaturated polyester with two different volume fraction of styrene. The gel time increases with the increasing of kenaf fiber weight fraction. The delay in gel time due to presence of kenaf fiber can be attributed to absorption of heat generated in the exothermic reaction [17]. At (10 wt %) the gel time was still the same compared to (0 wt %) but it affected the exotherm temperature and the time to peak. While for the (30 wt %) the curing was never stared and the exotherm temperature reached about 35 ºC at time to peak about 105 min, after that it started to decrease without any curing reaction for (60%up+40%st). Furthermore, for the resin ratio (50%up+50%st) the curing never started at kenaf weight fraction of (20 wt%) while the exotherm temperature has reached 37 ºC at the time to peak about 71 min and continued for 10 min at the same temperature before started decreasing due to heat loss to the environment. For same (30 wt%) fiber and resin (60%up+40%st) addition of 1% MEKP and 0.1% DMA causes the curing process to start and complete at the same circumstances with curing process; gel time and time to peak were same for resin with and without fiber. However, the exotherm was affected by decreases in temperature from 160.5 ºC to 102.3 ºC after adding of kenaf fiber.

Table 4 shows the minimum concentration of MEKP to start the curing process for different kenaf fiber weight fraction and styrene concentrations. Therefore; the

concentration ratio of MEKP increased with the increase of fiber weight fraction.

3.3.4 The Effect of Moisture Content

The effect of varying the level of water content on the exotherm behaviour of unsaturated polyester for 40% styrene is shown in Figure 9. At the onset of reaction of water with unsaturated polyester the rate of temperature increase is almost the same, but gelation time was increased. It is because the water slows the reaction by absorbing the heat from the system. Gel time was 35min for the 0% water, 38.5min for the 1vol% water, and 44 min for the 2vol% water. However, when the concentration of water was 3vol% water the gel time has decreased and reached 37min (2min) only above the 0% water ratio. That means after the 2% water concentration ratio there was no action affecting the gel time. Otherwise it may affect the mechanical properties. In addition, the water affected the action of initiator and accelerator system. Bubbles appear in the resin because the water can increase reactivity in some peroxide system as shown in Figure 10, the first specimen from the left side is 0vol% water, the second is with 1vol% water, and the last one is with 2vol% water.

Figure 9: Curing time for unsaturated polyester (60%up+40%st) with different volume fraction of water for 1% MEKP

Figure 10: Bubbles appear in the unsaturated polyester after adding water

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Table 1: Effect of affected of DMA ratio concentration on cure characteristic for different ratio of styrene at 1% MEKP at temperature surrounding 26 ºC

60%up + 40%st

DMA (Vol %) 0 0.1 0.2 0.3

Gel Time (min) 14 2.8 1.5 1

Time to Peak (min) 36 12.5 10 9.5

Exotherm Temperature (ºC) 133.4 160.5 165.1 168.1

50%up +50%st

Gel Time (min) 35 3 1.5 1

Time to Peak (min) 67.5 15 11 10

Exotherm Temperature (ºC) 128 190.2 192.1 191.3

40%up + 60%st

Gel Time (min) 23 2 1 0.8

Time to Peak (min) 46 11 8.5 7.5

Exotherm Temperature (ºC) 156 182.9 177.2 181.1

Table 2: Effect of affected of MEKP and DMA ratio concentrations on Tg Temperature for different styrene concentrations

60%up + 40%st

MEKP (vol %) 1 2 3 4

Tg (ºC) 148.58 149.51 147.54 144.96

DMA (vol %) for 1vol%MEKP 0 0.1 0.2 0.3

Tg (ºC) 148.58 143.91 146.37 149.44

50%up +50%st

MEKP (vol %) 1 2 3 4

Tg (ºC) 135.35 149.51 149.11 147.39

DMA (vol %) for 1vol%MEKP 0 0.1 0.2 0.3

Tg (ºC) 135.35 148.66 149.96 148.47

Table 3: Affected of kenaf fiber weight fraction on curing reaction for1% MEKP

Styrene ratio % Kenaf Fiber (wt %)

Gel Time (min)

Peak time (min)

Exotherm Temperature (ºC)

60%up + 40%st

0 19 36 133.4

10 14 29.5 131.8

20 33 51 89.8

30 Curing never started

50%up + 50%st

0 23 46 156

10 19 45 136.3

20 Curing never started

Table 4: The effect of constant kenaf weight fraction on curing reaction for different ratio of MEKP

Styrene ratio % MEKP (Vol %)

Gel Time (min)

Peak Time (min)

Exotherm Temperature (ºC)

60%up + 40%st + (30wt%) fiber

1 Curing never started

2 14 30 109.5

3 9 23 104.6

50%up + 50%st + (20wt%) fiber

1 Curing never started

2 20 35 109.8

3 12 26 114.7

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3.4 Mechanical Properties

3.4.1 Tensile Test

The tensile test was performed in accordance to ASTM (D638) specification. Four dumbbell shape (Type I) specimens from each matrix were tested in universal-testing machine (T-Machine), with load cell of 50KN. The specimen was loaded in tension at a speed of 5 mm/min. An extensometer of 50 mm gage length was mounted on the specimen for measurement of the strain. The cross section area of specimen was determined using a digital (caliper) Mitutoyo micrometre. The average results from four specimens were taken. Figure 11 shows the tensile test setup.

Figure 11: Tensile test T-Machine setup

3.4.2 The Effect of MEKP and Styrene Concentrations on Tensile Strength

The results of mechanical properties for the resin were calculated using Figure 12. The observed was the effect of MEKP concentration on the tensile strength of cured samples at a fixed (60%up + 40%st). It can be seen that the load increases to the maximum value and then suddenly decline as a brittle fracture was occurred in the material. The tensile strength does not significantly change with the increasing of MEKP ratio. In fact, the percentage of increase between the strength for 4% MEKP and the other ratio is less than 9% while the other ratios are (1, 2, 3) % about (2-3) %. The mechanical properties of the cured samples are varied from soft to hard, depending on the molar mass of the end

grouping. A high molecular mass will give a higher hardness, tensile and flexural strength of the final cured material. If the molecular mass is too low, the mechanical properties of the cured resin will be poor [4].

Figure 13 shows the photograph of matrix specimens after failure. It can be seen that the failures of specimen was in the gage zone and close to centre, which proves that the specimen fabrication was accurate. Styrene will generally add brittleness to the specimen, therefore the embrittlement causes decreasing the internal stresses in the part because of the increases in part shrinkage that occur with higher degrees of crosslinking. In another expression the tensile strength increases with decreasing of styrene concentration ratio at constant MEKP concentration as shown in Figure 14.

Figure 12: Effect of MEKP Ratio Concentration for (60%UP+40%ST) on the Tensile Stress and Strain

Figure 13: Photograph of the failed tensile test specimens for unsaturated polyester

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Figure 15 illustrated the effect of styrene ratio on the maximum strength of the unsaturated polyesters for different ratio of MEKP. In general it was observed that the maximum strength increases with decreasing of styrene ratio. In the first mixture of (60%up-40%st), the maximum strength was found at 4% MEKP, while the maximum strength for (50%up-50%st) start to decreased with the increasing of the initiator volume fraction until 2vol% of MEKP. Then the maximum strength has increased with the increase of MEKP concentration to the optimum value at 4% MEKP. Furthermore, the maximum strength for (40%up-60%st) start increase with the increasing of the initiator ratio until 3 vol% MEKP and the maximum strength decrease with the increase of MEKP ratio.

Figure 14: Effect of styrene concentration ratio on mechanical properties for unsaturated polyesters, 1 vol% MEKP

Figure 15: Effect of styrene concentration ratio on maximum strength for unsaturated polyester with different MEKP concentration

3.4.3 The Effect of MEKP and Styrene Concentrations on Tensile Modulus

Styrene ratio has an effect on the modulus of unsaturated polyesters for different ratio of curing agent MEKP and explained clearly in Figure 16. In fact, there insignificant change in modulus of elasticity with increasing of the initiator for unsaturated polyester mixture of (60%up-40%st), the maximum modulus was found to be at 2vol% MEKP. For the mixture of (50%up-50%st) the maximum modulus was found to be in 3vol% MEKP, while for (40%up-60%st) the modulus increase with the increasing of initiator ratio until 2%., then the modulus start decrease with the increasing of concentration ratio of the curing agent MEKP. This obviously proves that the unsaturated polyester with two different styrene concentration (60%up-40%st), (40%up-60%st) were found to have the same trend. Maximum tensile strength and the tensile modulus had the same trend, both of them decreasing with the increasing of the styrene volume fraction for the same volume fraction of the initiator, as shown in Figure 17.

Figure 16: Effect of styrene concentration ratio on modulus for unsaturated polyesters

3.4.4 The Effect of DMA Concentrations on Tensile Properties

The tensile strength and modulus of cured resins for various styrene concentrations at different DMA are shown in Figures 18 and 19, respectively. These results suggest that the strength for 40%st decrease with increasing of DMA, the decreasing percentage is about 23.5%. The results also absorbed that the strength increases for both 50%st and 60%st with increasing of DMA, the maximum improvement is about 59.2% for 50%st while for 60%st is more than double. The modulus

has the same trends for different DMA, it is consider that there insignificant change in modulus as can see from the decreasing or increasing percentage as follow, 5.7% the decreasing percentage for 40%st, 6.49% increasing percentage for 50%st and 14.2% increasing percentage for 60%st as Figure 19 show.

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Figure 17: Distribution of modulus and maximum tensile strength with different styrene concentrations

Figure 18: Effect of styrene concentration ratio on maximum strength for unsaturated polyester with different DMA concentration, 1vol% MEKP

Figure 19: Effect of styrene concentration ratio on modulus for unsaturated polyester with different DMA concentration, 1vol% MEKP

4. CONCLUTIONS

The conducted studies have revealed the following:

1. The physical parameters such as, viscosity and density is decrease with the increasing of environmental temperature and styrene concentration.

2. The styrene ratio controls the reactivity of the unsaturated polyester and also the crosslinking density of the final network by increasing the gel time, time to peak, and exotherm temperature.

3. Maximum strength and modulus of elasticity have the same trend for different concentration ratios of styrene and for certain concentration of styrene, different ratio MEKP and DMA have a significant effect on the maximum tensile strength, while DMA has insignificant effect on modulus of elasticity

4. The presence of kenaf fiber usually inanimate the crosslinking reactions, by added mass which is absorb the heat that occurs and delaying the gel time.

5. The moisture content in the resin effected the curing reaction by increasing the gel time and time to peak, while there insignificant effect on the exotherm temperature for the same MEKP concentration and same surrounding temperature.

6. The glass transition temperature Tg decrease with increasing of styrene concentration for 1vol% MEKP, beyond that there is insignificant effect on Tg with the increasing of MEKP and DMA.

5. ACKNOWLEDGMENT

The authors would like to thank everyone contributed to this research; and Swinburne University of Technology (SUT) for financial support.

6. REFRENCES

[1]. Andjelkovic, D. D., Culkin, D. A., and Loza R., Unsaturated polyester resins derived from renewable resources. COMPOSITES & POLTCON, American Composites Manufactures Association, January 15-17, (2009)

[2]. Shenoy, M. A., and. Melo, D. J. D., Evaluation of mechanical properties of unsaturated polyester-guar gum/hydoxypropyl guar gum composites. eXPRESS Polymer Letters 1, 622-628, (2007).

[3]. Sinha, R., Outlines of polymer technology. Prentice-Hall by India Private Ltd, New Delhi, 10001, (2000).

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40% UP + 60% ST

2

2.1

2.2

2.3

2.4

2.5

2.6

2.7

2.8

2.9

3

0 0.05 0.1 0.15 0.2 0.25 0.3

DMA (Vol%)

Te

nsile

Mo

du

lus (

Gp

a)

60% UP + 40% ST

50% UP + 50% ST

40% UP + 60% ST

Osman, E. A. et al., Malaysian Polymer Journal, Vol. 7, No. 2, p 42-55, 2012

MPJ 55

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