Effect of Rice Husk Particle Size on Tensile and Density of Recycled PPVC Composite

FARAH NORDYANA Azizul Rahman1,a, AHMAD ZAFIR Romli2,b and Mohd Hanafiah Abidin2,c

1Faculty of Applied Sciences, Universiti Teknologi MARA, 40450 Shah Alam, Selangor, Malaysia

2Center of Polymer Composite Research and Technology (PoCResT), Institute of Science, Level 3, Blok C, Universiti Teknologi MARA, 40450 Shah Alam, Selangor, Malaysia

afarahnordyana@yahoo.com, bahmad349@salam.uitm.edu.my, cmohdh615@salam.uitm.edu.my

Keywords: Rice Husk, PPVC, Wood Plastic Composite (WPC), Tensile Test, Density Test

Abstract. This study is to measure the effect of various rice husks’ particle size on density, tensile

strength, Young’s modulus and elongation at break of PPVC composite. Rice husk was grind before

being sieved to particle sizes of ≤ 60 µm, 60 µm < particle size ≤ 80 µm, and 80 µm < particle size

≤ 100µm. Each size was compounded with PPVC at same filler loading which is 20 % rice husk

and being pressed using hot press machine. Tensile strength, Young’s modulus and elongation at

break increased as particle size increases. The highest value for tensile strength, Young’s modulus

and elongation at break are 21.48 MPa, 1344.88 MPa and 2.29 % respectively. However, it is

different for density result which decreased as particle size increases. The results obtained from the

study shows that the bigger the size of the rice husks, the better the composite tensile properties.

Introduction

High concern for environment safety has created many interests in thermoplastic matrix composite

for application of natural material containing natural cellulose filler such as hemp, sisal, wood flour,

rice husk and other natural fibre. Natural fillers are inexpensive and have high biodegradability

properties that can help to reduce environmental pollution.

Wood plastic composites or widely known as WPC is an alternatives product to traditional wood

product. WPC act as wood replacement due to its flexibility in construction, attractive, available

and affordable. WPC is one of the new materials that use natural fiber or wood fiber such as rice

husk as filler [1]. This natural fillers gain high attention from researcher because it is inexpensive

and has biodegradability properties that lead to reducing environmental degradation [2, 3]. Organic

natural filler is preferable than inorganic natural filler such as silica because of their low density,

easy recyclability, bio-degradability and renewable nature [4].

Polyvinyl chloride (PVC) is one of the major thermoplastic used today in many products such as

electronic items, stationaries, wires, constructional materials, chemical equipments, cables etc.

PPVC produced in a huge amount worldwide. It has more process ability and thermal stability

compared to other commodity plastics like polyethylene and polystyrene. PPVC has high tensile

strength and good chemical resistance [5]. It is one of the major thermoplastic uses today [6].

Plasticised PVC is one type of PVC that is very soft and flexible. It also has low melt viscosity and

high elongation at break compared to unplasticised PVC.

The use of recycled plastic as raw material source of WPC has been studied by a number of

authors such as Mohammad et al. [9]. Hence, the development of WPC product, with the intended

of utilizing the problematic waste residual would be desirable [9]. The main objective of this

research is to determine the effect of RH particle size as filler for recycled PPVC composite.

Advanced Materials Research Vol. 812 (2013) pp 145-150Online available since 2013/Sep/10 at www.scientific.net© (2013) Trans Tech Publications, Switzerlanddoi:10.4028/www.scientific.net/AMR.812.145

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Experimental

Materials and Test Instruments. Rice husk was supplied by Malaysian Agricultural Research and

Development Institute (MARDI) Alor Star, Kedah, Malaysia. Recycled Plasticised Polyvinyl

Chloride (PVC) sheet was obtained from Polymer Laboratory, Faculty of Applied Sciences,

Universiti Teknologi MARA (UiTM) Shah Alam, Selangor, Malaysia. Hydraulic hot press HP25T

was used for moulding process. Dencimeter Shimadzu UX420S was used for density test, while

Shimadzu Autograph AG-X was used for tensile testing. Recycled PPVC sheet was grinded using

Fritsch Pulverisette 15 with 1000µm sieve size. The sample was cut using precision cutting

machine. Hammer mill was used to grind rice husk before being sieved. Laboratory sieve shaker

SS-200 was used to sieve the rice husk into desired particle size.

Sample Preparation. The first stage, PPVC sheet was cut to smaller pieces using a pair of

scissors. Then, it was feed into the grinder (1000 µm sieve size) for finer particle size. The rice husk

was grind using hammer mill (250 µm sieve size) before being sieved. The rice husk (RH) was

sieved into different RH particle sizes which is less and equal to 60 µm, greater than 60 µm to 80

µm, and greater than 80 µm to 100 µm. The PPVC and rice husk (80:20) was mixed and poured

into 15 cm × 15 cm × 0.3 cm mould and pressed at 180 °C for 30 min before left to cool at room

temperature at about 24 hours. The sample was then cut to specific dimension for tensile and

density test.

Testing Method. For tensile test, 15 cm length × 2 cm width sample with 80 mm gauge length

was tested at the speed of 5 mm.min-1

. The density test was determined using sample dimension of

1 cm length × 1 cm width × 0.3 cm thickness.

Results and Discussion

Tensile Strength. From Fig. 1, tensile strength increased as particle size increases. This result is

contradicting from what Crespo et al. [2] found in their research, where the smaller particles

improve the mechanical properties due to better dispersion and alignment of the particles within the

matrix.

Fig. 1 Effect of RH particle size on tensile strength of recycled PPVC composite

From the research, it was found that the smaller particle size will tend to agglomerate, thus

reduced the interaction between filler and matrix as refer to SEM micrograph in Fig. 2.

146 Progress in Polymer and Rubber Technology

(a) (b) (c)

Fig. 2 SEM morphology of recycled PPVC composite at different RH particle size: (a) RH particle

size ≤ 60 µm; (b) 60 µm < RH particle size ≤ 80 µm; (c) 80 µm < RH particle size ≤ 100 µm

Tensile Modulus. Tensile modulus is the measure of stiffness and elasticity of elastic materials.

Fig. 3 shows that tensile modulus increased as particle size increases. The result agreed with the

conclusion by Duan et al. [1], which state that the increasing in fiber length will result to higher

tensile modulus due to better interaction between matrix and filler.

Fig. 3 Effect of RH particle size on tensile modulus of recycled PPVC composite

Elongation at Break. Elongation at break is used to describe the ductility of a material. Fig. 4

shows that elongation at break increased as particle size increases. This is because of the better

interaction between matrix and filler and also the possibility of good dispersion as shown in Fig. 2

(b) and Fig. 2 (c). Good dispersion and bonding between filler and matrix tend to increase tensile

strength. This result agrees with the report by Lu et al. as the tensile strength improves will lead to

high elongation at break [1].

430× 405× 450×

Advanced Materials Research Vol. 812 147

Fig. 4 Effect of RH particle size on elongation at break of recycled PPVC composite

Density. Density is a physical property of matter which defined as a mass per unit volume. Fig. 5

shows that density decreased as particle size increases. The expected density can be calculated

using Eq. 1. Void volume fraction was calculated using Eq. 2 [7]. The density of bulk rice husk is

1.3 g.cm-3

[8].

Fig. 5 Effect of RH particle size on density of recycled PPVC composite

ρ = v1ρ1 + v2ρ2 . (1)

Where v1 and v2 is the volume fraction of component 1 and 2 with density ρ1 and ρ2 respectively.

. (2)

Where ρct is the expected density of composite with no voids and ρce is experiment measured

density of composite.

148 Progress in Polymer and Rubber Technology

Fig. 6 Void volume fraction of recycled PPVC composite

Density of composite decreased as RH particle size increases because of more void in recycled

PPVC composite as shown in Fig. 6. The formation of void is due to the porous nature of rice husk

[4] as shown in Fig. 7. Due to its low density, the prepared composite will be useful in applications

that require low weight but high strength properties [8].

Fig. 7 SEM morphology of rice husk cutting surface

Conclusion

From the study, tensile strength, tensile modulus and elongation at break of this recycled PPVC

composite increased as particle size increases. Density of composite decreased as particle size

increases. From the result obtain, it can be concluded that RH particle size greater than 80 µm to

100 µm has optimise mechanical properties.

Acknowledgements

The author would like to thank the Faculty of Applied Sciences, Universiti Teknologi MARA for

the facilities in doing the compounding and fabrication of the samples. Author appreciation also

goes to the Malaysian Agricultural Research and Development Institute (MARDI) for rice husk and

Center of Polymer Composite Research and Technology (PoCResT) for the calibrated testing

equipment in completing this research.

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Advanced Materials Research Vol. 812 149

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150 Progress in Polymer and Rubber Technology

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