The Effect of Binder on Mechanical Properties of Kenaf Fibre/Polypropylene Composites using Full Factorial Method

Mohd Amran1,a, Raja Izamshah1,b, Mohd Hadzley1,c, Mohd Shahir1,d, Mohd Amri1,e, Mohd Sanusi1,f, Hazwani Hilmi1,g

1Faculty of Manufacturing Engineering, Universiti Teknikal Malaysia Melaka, Hang Tuah Jaya 76100 Durian Tunggal, Melaka, Malaysia.

amohdamran@utem.edu.my, bizamshah@utem.edu.my, chadzley@utem.edu.my, dshahir@utem.edu.my, emohdamri@utem.edu.my, fmohdsanusi@utem.edu.my,

ghazwanihilmi@gmail.com

Keywords: Kenaf Fiber; Polypropylene; MAPP; Tensile; Modulus; Elongation

Abstract. The effect of maleated polypropylene (MAPP) as binder on the mechanical properties of

kenaf fibre/polypropylene (KF/PP) composites is studied. Ratios between kenaf fibre and PP having

10:90, 30:70 and 50:50 in weight ratio were selected. Further, MAPP having 1, 3 and 5 percent in

percentage of weight ratio was mixed in KF/PP composites. Hot press machine was used to produce

tensile test samples of KF/PP composites. The mechanical properties that are tensile strength,

tensile modulus and elongation at break of KF-PP composites were obtained from tensile test result.

It is found that the tensile strength and tensile modulus increase with increasing the kenaf fibre

loading and higher percentage of MAPP. Further, the elongation at break for KF/PP composites

shows lower result when increasing of kenaf fibre loading. However, when percentage of MAPP

added in KF/PP composites increases, the elongation at break increased slightly. Thus, result shows

that kenaf fibre/PP composites with binder were better in tensile strength, tensile modulus however

the elongation at break shows weak result unless the binder was added.

Introduction

Nowadays, various composites made from natural fibre are become commercialized and widely

used as reinforcement in polymer composites. The natural fibres have their advantages which they

are low cost, lightweight, easy to find and high strength to weight ratio. Therefore, the demand of

natural fiber in the manufacturing industry is increasing. This is due to the lack of sources and the

increasing construction materials which based on mineral sources such as steel, aluminium and

forest trees. Various types of reinforcement have been used in polymer composites such as

reinforcement made from PTFE fibre in PP [1], fine fibre [2], kenaf fibre [3] and natural fibre [4].

Almost all reinforcement materials have been used in polymer composites enhances the mechanical

properties [5], rheological properties [6], and physical properties [7]. Binder materials have been

used in polymer composites for enhances the contact between fibre as reinforcement with polymer

as matrix. Various types of binder have been used such as silane, alkoxysilane, maleic-anhydride

grafted polypropylene (MAPP) and etc. MAPP is widely used as its function to enhance the

interactions between reinforcement and matrix. Further, the function of MAPP on polypropylene

composites is also to strengthen the binder between reinforcement and matrix [8]. Therefore, the

purpose of this project is to find out the effect of binder on the mechanical properties of

polypropylene mixing with kenaf fibre having different ratio. The design of experiment using full

factorial experimental design was used and the responses of mechanical properties were analyzed

through statistical method using Minitab software version 16.

Experimental

Kenaf fibre was used as filler and Propelinas G112 polypropylene was used as matrix purchased

from Polypropylene (M) Sdn. Bhd. with a density and melt index specified as 0.9 g/cm3 and 11 g/10

min at 230oC, respectively. Polypropylene-graft-maleic anhydride which is a commercially name as

maleated polypropylene (MAPP) was selected as the binder for kenaf fibre in polypropylene

composites. The kenaf fiber filler was cut into smaller length using scissor before it was blend in

blender. The filler was then sieved using a vibratory sieve-shaker machine to get the filler size of

120μm to 0.634μm. Compounding of the composite materials was carried out using an internal

batch mixer. The propeller speed was set at 25 rpm with temperature of 180˚C. The MAPP was

loaded while compounding process of kenaf fibre and polypropylene. The concentrations MAPP

used are 1%, 3% and 5% (w/w). The compounds were unloaded after 15 min of compounding

process. The compounds were transferred to a compression mould with dimensions of 200mm x

200mm x 3mm. Then, the compounds were preheated for 10 min at 200˚C followed by heating at

the same temperature for 10 min with pressure of 40 kgf and then cold press for 10 min with the

same pressure. Three ratios of the kenaf fiber-PP mixtures used were: 10:90, 30:70 and 50:50

(w/w). The kenaf fibre/PP compositions and binder percentage used in this study were listed in

Table 1. With the help of Minitab software to analyze the result, full factorial experimental design

was selected and data were analyzed the main effects of responses. Two factors that are kenaf

fibre/PP ratio and percentage loading of binder, and three levels were used in this experiment. There

are 9 runs were performed with 3 replications from the equation of full factorial design.

Table 1: Formulations of KF/PP composites and MAPP

Factor Level

A Kenaf fibre/PP 10/90 30/70 50/50

B MAPP 1 3 5

Result and Discussion

Result of experimetal material charateritics on tensile strength, modulus strength and elongation

at break is shown in Figure 1.

Figure 1: Mechanical properties for tensile strength, modulus strength and elongation at break.

Tensile Strength

Figure 1 shows that tensile strength of the KF/PP composites treated with MAPP increases as the

MAPP loading increased. Result shows that composites treated with binder at 3% for samples 4, 5,

6 and 5% for samples 7, 8, 9 display better tensile strength than those at 1% for sample 1, 2, and 3.

This is because the incorporations of binder had enhanced the tensile strength of composites, which

may be due to a good compatibility at interfacial regions between filler and matrix. M.J. Saad said

that it was believed that a good filler-matrix interaction could be derived from the formation of an

ester bond between the anhydride groups of epolene 43 and the hydroxyl groups at the surfaces of

kenaf filler [9]. Figure 2 shows that main effects of kenaf fibre for tensile strength where it is the

most significant factor affected the KF/PP composites as compare to the MAPP. Further, surface

plot shows clearly that increasing kenaf fibre in KF/PP composites enhances the tensile strength.

The increases of strength of KF/PP composites become prominent when the loading of MAPP

increased from low ratio to high ratio of KF/PP compositions.

5010

23.5

23.0

22.5

22.0

21.5

21.0

20.5

20.0

51

Kenaf Fibre

Me

an

MAP

Main Effects Plot for TensileData Means

5.5

4.022

23

2.5

24

10

25

251.040

55

Tensile

MAP

Kenaf Fibre

Surface Plot of Tensile vs MAP, Kenaf Fibre

Figure 2: Tensile strength result (a) Main effects and (b) surface plot

Tensile Modulus

The tensile modulus of the KF/PP composites increases as the MAPP binder loading increased

which can be seen clearly in Figure 1. According to results of tensile modulus in Figure 1, it

indicates that the MAPP binder is able to enhance the stiffness of the composites. The binder ratio

at 5% displays a higher modulus than at 1% and 3% especially at KF/PP composites having ratio

30/70 and 50/50 compositions. This may be due to the more anhydride group from epolene 43

binder that connected with hydroxyl groups from kenaf fibre. Apart from that, the tensile modulus

had increased as the filler loading increased which can be seen in Figure 1. This is a common

phenomenon, which has been reported by other researcher in the case of kenaf-PP composites with

Epolene-43. Since kenaf filler has a more inherent stiffness than the matrix, the increase in filler

loading had increased the stiffness of the composites [10]. Figure 3 shows that kenaf fibre is the

most significant factor affected the tensile modulus as compared to the MAPP binder. Surface plot

in the figure shows that when loading of kenaf fibre increases the responses of tensile modulus

increasing significantly. However, increasing of MAPP binder on the KF/PP composites reduce the

tensile modulus as compare low loading of MAPP binder.

5010

25.0

22.5

20.0

17.5

15.0

51

Kenaf Fibre

Me

an

MAP

Main Effects Plot for ModulusData Means

5.5

4.015

20

2.510

25

251.040

55

Modulus

MAP

Kenaf Fibre

Surface Plot of Modulus vs MAP, Kenaf Fibre

Figure 3: Tensile modulus result (a) main effects and (b) surface plot

Elongation at Break The percentage of elongation at break of sample contains more filler decreases as shown in Figure

1. This may due to the hydrogen bonding which has made the filler bundled thus weaken the

sample. Kenaf and PP compositions having ratio of 10:90 with binder show the higher elongation at

break rather than other formulations of KF/PP composites. The trend line observed on others

researcher studied shows the same trend which more filler loading decreased the elongation at break

value [11]. Loading of kenaf fibre in KF/PP composites shows more significance as compare to the

MAPP as shown in Figure 4 (a). Further, Figure 4 (b) shows that lower the percentage of binder in

KF/ PP composites reduces the elongation at break marginally significance.

5010

1.2

1.1

1.0

0.9

0.8

0.7

0.6

0.5

0.4

51

Kenaf Fibre

Me

an

MAP

Main Effects Plot for ElongationData Means

5.5

4.0

0.50

0.75

2.5

1.00

10

1.25

251.040

55

Elongation

MAP

Kenaf Fibre

Surface Plot of Elongation vs MAP, Kenaf Fibre

Figure 4: Elongation at break result (a) main effects and (b) surface plot

Conclusion

The study shows that the tensile and modulus strength of kenaf-PP composites are enhanced

by adding binder. The higher the binder loading in KF/PP composites, the better are mechanical

properties for both tensile and modulus strength but lower when it comes to elongation at break. In

conclusion, adding a small percentage of MAPP in Kenaf fibre/Polypropylene composites plays an

important role as it determines the mechanical properties values.

Acknowledgements

The authors gratefully acknowledge the Universiti Teknikal Malaysia Melaka (UTeM) for

supporting this research under grant research no. FRGS/1/2014/TK01/FKP/02/F00224.

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