Recycled High Density Polyethylene/Ethylene Vinyl Acetate …akademiabaru.com/doc/ARMSV3_N1_P1_7.pdf · polyethylene/ethylene vinyl acetate/taro filler. This research needs to be

Journal of Advanced Research in Materials Science

ISSN (online): 2289-7992 | Vol. 3, No.1. Pages 1-7, 2014

1

Penerbit

Akademia Baru

Recycled High Density Polyethylene/Ethylene

Vinyl Acetate (RHDPE/EVA)/Taro Powder

(Colocasia esculenta) Composites: The Effect of

Caprolactam-Maleic Anhydride on Tensile

Properties and Morphology

A. R. H. Fatimah*,1,a, A. G. Supri2,b and Z. Fairuz1,c

1School of Materials Engineering, Universiti Malaysia Perlis (UniMAP), Kompleks Taman

Muhibah, Jejawi 2, 02600 Arau, Perlis, Malaysia. 2Faculty of Engineering Technology, Universiti Malaysia Perlis (UniMAP), Main Campus,

Pauh Putra, 02600 Arau, Perlis, Malaysia. a,*[email protected], [email protected], [email protected]

Abstract – Natural fillers fulfil most requirements needed to replace synthetic fillers in thermoplastic

composites. However, some disadvantages appear when natural fillers are used for composites. The

poor compatibility between the hydrophilic fillers with the hydrophobic polymer matrix leads to a

weak interface and hence, poor mechanical properties. In this research, the caprolactam-maleic

anhydride (CL-MAH) was used as a compatibilizer. The tensile strength of RHDPE/EVA/Taro powder

composites decreased with increasing filler loading, while adding caprolactam-maleic anhydride in

the composite significantly improved the tensile properties. The SEM morphology of tensile fracture

surfaces of RHDPE/EVA/Taro powder composites shows better interfacial interaction between taro

powder and RHDPE/EVA phases with the incidence of CL-MAH as a compatibilizer. Copyright ©

2014 Penerbit Akademia Baru - All rights reserved.

Keywords: Recycled High Density Polyethylene, Ethylene Vinyl Acetate, Taro Fillers, Caprolactam-Maleic

Anhydride

1.0 INTRODUCTION

Polymer composites have been widely used for several years to meet the demand for

materials that provide higher standards of performance and reliability [1,2]. Composites are

combinations of at least two materials, which are matrix and filler as reinforcement. The

matrix material surrounds the filler by maintaining their relative positions [3,4]. The use of

natural fillers as reinforcement of composites receives a lot of attentions from many plastic-

based industries. These natural fillers offer such advantages as low weight, widely available,

enhanced biodegradability, low cost, high filling levels possible, and high specific

mechanical properties of composites [5,6,7]. However, poor interfacial properties in the form

of poor adhesion between the hydrophilic lignocellulosic fillers and hydrophobic matrices

reduce the potential of natural fillers as reinforcing agents and weaken the mechanical

properties of the final composites. The interface, which is an important aspect to determine

the physical and mechanical properties of composites, can be improved by the use of

compatibilizing agents. Compatibilizers have the ability to react with organic fillers and



2

Penerbit

Akademia Baru

matrices, forming bridges across the interface [8,9]. The aims of this study are to investigate

the effects of different taro filler loadings and the use of caprolactam-maleic anhydride as a

compatibilizer on the tensile properties and morphology of recycled high density

polyethylene/ethylene vinyl acetate/taro filler. This research needs to be improved by refining

the reaction of two different compatibilizers, caprolactam and maleic anhydride, hence,

improved the blending of RHDPE with EVA. Besides that, the addition of filler loading also

needs to be enhanced because this will lead to superior tensile properties, which makes taro

powder as useful organic filler for commercial product.

2.0 METHODOLOGY

2.1 Materials. RHDPE with melt flow index of 0.7 g/10 min (190°C) and density of 939.9

kg/m3 was used. EVA, which contains 18.1 wt% VA, melt index of 2.5 g/10 min (80°C, 2.16

kg) and density of 0.93 g/cm3 was supplied from A.R. Alatan Sdn. Bhd., Kedah Darul Aman,

Malaysia. Taro filler was obtained from a local village in Selangor. The ingredients of taro

are shown in Table 1. Maleic anhydride was supplied by Zarm Scientific & Supplier Sdn.

Bhd., Penang, Malaysia. Caprolactam and dibenzoyl peroxide (BPO) were obtained from

A.R. Alatan Sdn. Bhd., Kedah Darul Aman, Malaysia.

Table 1: Ingredients of taro powder (TP) as determined from the Laboratory Department of

DXN Holdings Bhd., Jitra, Kedah.

Content Quantity

Calories (Kcal) 274.0

Carbohydrate (%) 52.6

Fat (%) 1.2

Protein (%) 13.1

2.2 Sample Preparation. The stems from taro plants were cut, washed, dried, and grinded to

powder by using a grinder machine. Taro fillers with average sizes of 75 µm were dried in a

vacuum oven at 80°C for 1 h. For composites preparation, the compounding of the blends

was carried out by melt blending in a Brabender internal mixer. The RHDPE was first mixed

in the internal mixer at 160°C with the speed of 50 rpm for 2 min, followed by the addition of

EVA and mixed until homogenous. The compatibilizers, CL-MAH, dibenzoyl peroxide

(DBP), and TP were added to the mixer for the remaining minutes. Each of the compounding

step was compression molded into sheets of 2 mm thickness using a hydraulic press at 160°C

for 6 min and cooled under pressure for 4 min. Table 2 shows the formulation used in this

study.



3

Penerbit

Akademia Baru

Table 2: Formulations of RHDPE/EVA/TP composites and RHDPE/EVA/TP-CL-MAH

composites.

Composite Code RHDPE

[phr]

EVA

[phr]

TP

[phr]

CL-MAH

[phr]

DBP

[phr]

RHDPE/EVA/TP5 80 20 5 - -

RHDPE/EVA/TP10 80 20 10 - -

RHDPE/EVA/TP15 80 20 15 - -

RHDPE/EVA/TP20 80 20 20 - -

RHDPE/EVA/TP25 80 20 25 - -

RHDPE/EVA/TP5-CL-MAH 80 20 5 6 1





2.3 Characterization and Measurements. Tensile properties of the composites were

measured by using Universal Testing Machine Instron 5582 with crosshead speed of 30

mm/min. Dumbbell-shaped specimens were conditioned at ambient temperature before

testing. Studies on surface morphology of the RHDPE/EVA/TP composites with and without

compatibilizer were carried out using SEM. Surfaces of the samples were coated with a thin

platinum layer about 12 µm thickness using the Auto Fine Coater to avoid electrostatic

charged during examination.



4

Penerbit

Akademia Baru

3.0 RESULTS AND DISCUSSION

3.1 Tensile Properties

Fig. 1(a) shows the effect of different filler loadings of taro fillers on the tensile strength of

RHDPE/EVA composites. The results show that the tensile strength of RHDPE/EVA/Taro

powder composites decreased with the increase in taro fillers content. Such decline in tensile

strength is credited to the weak bonding formed between the polar hydrophilic taro fillers and

non-polar hydrophobic RHDPE/EVA composites. The increase in filler content also resulted

in agglomeration of dispersed filler particles and consequently reduced the tensile strength

due to the lower strength of the agglomerates. Similar results were testified by Kim et al.

[10], where for the addition of bio-flour loading, the tensile strength of the composites

decreased due to weak interfacial adhesion between hydrophilic bio-flour and hydrophobic

polypropylene. In addition, Fig. 1(a) also indicates that the tensile strength of the

RHDPE/EVA/Taro powder composites increased with the presence of CL-MAH. The result

suggests that the interfacial adhesion has evidently improved between the RHDPE/EVA

phases and the taro powder, leading to an improvement of tensile strength of the composites

[11,12]. Liu et al. [13] conducted a study on the effect of two modifiers, PE-g-MAH and

maleated ethylene/propylene elastomers (EPR-g-MAH) on the matrix of HDPE and bamboo

flour (BF), which resulted in increased tensile strength of the composites compared to

HDPE/BF composites alone.

(a) (b)

Figure 1: Tensile properties of RHDPE/EVA/Taro powder composites and

RHDPE/EVA/Taro powder/CL-MAH composites with different filler loadings (a) Tensile

strength and (b) elongation at break

Fig. 1(b) also shows the effect of different filler loadings and compatibilizer on elongation at

break of RHDPE/EVA/Taro powder composites. The addition of taro powder with different

filler loadings reduced the toughness of the RHDPE/EVA composites. As taro filler

increased, the elongation at break decreased gradually as the filler forces the matrix to deform

0

5

10

15

20

5 10 15 20 25Te

nsi

le S

tre

ng

th (

Mp

a)

Filler Loadings (phr)

RHDPE80/EVA20 RHDPE80/EVA20/CL-MAH

0

50

100

150

200

250

300

5 10 15 20 25

Elo

ng

ati

on

at

Bre

ak

(%

)

Filler Loadings (phr)

RHDPE80/EVA20 RHDPE80/EVA20/CL-MAH



5

Penerbit

Akademia Baru

more than the overall deformation of composites due to the fact that deformation of filler is

commonly less than matrix. At similar filler loading, the RHDPE/EVA/TP/CL-MAH

composites had lower elongation at break than RHDPE/EVA/TP composites. This is due to

good interfacial adhesion between filler and matrix, which then increased the stiffness of the

composites and consequently reduced the elongation at break [10].

3.2 Morphology Analysis

Fig. 2 shows SEM micrograph of tensile fracture surface of RHDPE/EVA/TP and

RHDPE/EVA/TP/CL-MAH composites at different taro powder loadings. Figs. 2(a), 2(b),

and 2(c) show the incompatibility of the composites, as the fracture surfaces indicate weak

adhesion between the matrix and taro powder due to the presence of many voids within the

surface. This low adhesion had given rise to poor stress transfer across the interfaces when

stress was applied. The number of voids positioned in the fracture surfaces was due to poor

dispersion of taro powder in RHDPE/EVA blends. The amount of voids increased with

increasing content of filler due to the absence of a compatibilizer. The addition of CL-MAH

as a compatibilizer improved the interfacial adhesion between taro powders with

RHDPE/EVA phases as shown in Figs. 2(d), 2(e), and 2(f). By closely examining these three

figures, it could be observed that the filler was strongly bonded to the polymer due to less

microvoids and filler-matrix debonding in the interphase region. A similar observation was

reported by Ayrilmis et al. [10] for the compatibilization of composites. In addition, due to

the presence of a compatibilizer, the tensile fractured surfaces have rough and good

interaction between the filler and the matrix.

(a) (b) (c)

(d) (e) (f)

Figure 2: Scanning electron micrographs of tensile fracture surfaces of RHDPE/EVA/TP

composites and RHDPE/EVA/TP/CL-MAH composites with different filler loadings. (a)

RHDPE/EVA/TP-5, (b) RHDPE/EVA/TP-15, (c) RHDPE/EVA/TP-25, (d)



6

Penerbit

Akademia Baru

RHDPE/EVA/TP-5/CL-MAH, (e) RHDPE/EVA/TP-15/CL-MAH, (f) RHDPE/EVA/TP-

25/CL-MAH.

4.0 CONCLUSION

The RHDPE/EVA/TP/CL-MAH composites have higher tensile strength but lower

elongation at break compared to RHDPE/EVA/TP composites. The addition of CL-MAH as a

compatibilizer improved the compatibility and stress transfers of the composites and

simultaneously improved the interfacial adhesion between taro powder and RHDPE/EVA

phases.

REFERENCES

[1] F.P. La Mantia, M. Morreale, Green composites: A brief review, Composites: Part A

42 (2011) 579-588.

[2] F. Klaus, F. Stoyko, Z. Zhong, Polymer Composite, from Nano- to Macro-Scale,

Springer, Berlin, 2005.

[3] R.N. Rothon, Particle-filled Polymer Composites, second ed., Rapra Technology,

Shrewsbury, UK, 2003.

[4] A.R.H. Fatimah, A.A.H. Ikmal, A.G. Supri, Effect of PEgMAH on tensile properties

and swelling behavior of recycled high density polyethylene/ethylene vinyl

acetate/waste tyre dust (r-HDPE/EVA/WTD) composites, Advance Mechanics and

Materials 554 (2014) 137-140.

[5] D.N. Saheb, J.P. Jog, Natural fiber polymer composites: A review, Advances in

Polymer Technology Vol. 18 No. 4 (1999) 351-363.

[6] N. Stevulova, E. Terpakova, J. Cigasova, J. Junak, L. Kidalova, Chemically treated

hemp shives as a suitable organic filler for lightweight composites preparing, Procedia

Engineering 42 (2012) 948-954.

[7] R. M. Rowell, Challenges in biomass-thermoplastic composites, J Polym Environ 15

(2007) 229-235.

[8] N. Bakar, C.Y. Chee, L.C. Abdullah, C.T. Ratnam, N. Azowa, Effect of methyl

methacrylate grafted kenaf on mechanical properties of polyvinyl chloride/ethylene

vinyl acetate composites, Composites: Part A 63 (2014) 45-50.

[9] V. Mittal, Functional Polymer Blend: Synthesis, Properties, and Performance, Taylor &

Francis Group, FL, 2012.

[10] H.S. Kim, B.H. Lee, S.W. Choi, S. Kim, H.J. Kim, The effect of types of maleic

anhydride-grafted polypropylene (MAPP) on the interfacial adhesion properties of bio-

flour-filled polypropylene composites, Composites: Part A 38 (2007) 1473-1482.

[11] K. Ahmed, N.Z. Raza, F. Habib, M. Aijaz, M.H. Afridi, An investigation on the

influence of filler loading and compatibilizer on the properties of polypropylene/marble



7

Penerbit

Akademia Baru

sludge composites, Journal of Industrial and Engineering Chemistry 19 (2013) 1805-

1810.

[12] N. Ayrilmis, A. Kaymakci, F. Ozdemir, Physical, mechanical, and thermal properties of

polypropylene composites filled with walnut shell flour, Journal of Industrial and

Engineering Chemistry 19 (2013) 908-914.

[13] H. Liu, Q. Wu, G. Han, F. Yao, Y. Kojima, S. Suzuki, Compatibilizing and toughening

bamboo flour-filled HDPE composites: Mechanical properties and morphologies,

Composites: Part A 39 (2008) 1891-1900.

Documents

Recycled High Density Polyethylene/Ethylene Vinyl Acetate …akademiabaru.com/doc/ARMSV3_N1_P1_7.pdf · polyethylene/ethylene vinyl acetate/taro filler. This research needs to be