performance of recycled high density polyethylene (hdpe)/ rice husk

PERFORMANCE OF RECYCLED HIGH DENSITY POLYETHYLENE

(HDPE)/ RICE HUSK COMPOSITE INJECTION GRADE IN

THERMOFORMING PROCESS

FATIMAH ZAHARAH BINTI CHE MOHAMAD

A report submitted in partial fulfillment

of the requirement for the award of the degree of

Bachelor of Engineering (Chemical-Polymer)

FACULTY OF CHEMICAL AND NATURAL RESOURCES ENGINEERING

UNIVERSITI TEKNOLOGI MALAYSIA

MAY, 2007

iii

Special dedication to my beloved mom and dad, also to my sisters and brother...

iv

ACKNOWLEDGEMENT

These five months had been quite tough and gave many challenging in finishing

the final year project. Without the help of the following individuals, this thesis will just

be a dream.

Firstly, I would to thank Universiti Technologi Malaysia, for giving me the

opportunity to carry out this final year undergraduate project and providing the useful

equipments.

Big thanks also go to my honourable supervisor, PM Dr. Wan Aizan Wan Abd.

Rahman, for helping and guiding me in various aspects through the progression of this

project. Also very thankful to Pn. Roshafima who supervised me during my supervisor

on leave. Not forgetting all staff and laboratory technicians for their willingness to help

and guide me during my research.

Finally, I would like to extend my heartfelt gratitude to all my course mate and

friends who offer needed tips, advice and endless cooperation. Without those helps, this

research report would not have been completed successfully. To my lovely parents and

family, thanks for the spiritually encouragement and very understanding.

v

ABSTRACT

All thermoplastic polymers can be remelted and recompounded into a new

grade, but the presence of certain additives, blends, or fillers like glass fibers may

limit the application area of the recyclate. In this present study, it was my aim to

investigate the ability of recycled rice husk-filled-high density polyethylene (RHPE)

composite injection grade to be processed using thermoforming technique. Various

recycled RHPE composite injection grade, that is with composition 30%, 40% and

50% of rice husk were investigated in this study. These composites were first grinded

to a fine form using laboratory grinder machine before being melt-blended and

milled into sheets on a two-roll mill. Then, test specimens were prepared to study on

the mechanical properties that is tearing test and tensile test. The results showed the

tear and tensile strength were reduced significantly with the percentage increase of

rice husk contents. However, the Young modulus had increased. The MFI of the

recycled RHPE was determined to find its suitability in terms of flow behaviour and

compared to standard MFI for thermoform grade. MFI was found to decrease as

compared to the virgin HDPE, but is within the standard MFI for thermoforming

material grade. FTIR spectroscopy and DSC thermal analysis used to characterize the

recycled composite materials. FTIR analysis indicates that the major chemical

structure of rice husk filled in HDPE samples is not affected by recycling process

and also shows the rice husk contents was not undergo degradation during the

injection moulding process. While, melting temperature does not differ much from

the pure RHPE therefore recycled RHPE does not undergo much thermal

degradation. So, these shows the ability of recycled RHPE composite can be

reprocessed for other usage. Recycled RHPE composites containing 40% rice husk

exhibit good properties and showed high capability to be thermoformed.

vi

ABSTRAK

Semua polimer termoplastik boleh dilebur dan di sebatikan semula kepada gred

yang baru, tetapi dengan kehadiran bahan penambah, bahan campuran yang tertentu atau

pengisi seperti fiberglass, mungkin akan mengehad bidang aplikasi bahan yang dikitar

semula. Maka, objekif kajian ini adalah untuk menyiasat kebolehan komposit kitar

semula polietilena berketumpatan tinggi terisi sekam (RHPE) padi gred suntikan untuk

diproses pembentukan haba. Terdapat tiga komposisi produk komposit RHPE gred

suntikan ini digunakan dalam kajian ini, iaitu 30%, 40% and 50% kandungan sekam padi.

Produk komposit ini terlebih dahulu dikisar/ dihancurkan menggunakn alat pengisar

makmal bagi menghasilkan serbuk halus sebelum di adunleburkan dan menghasilkan

kepingan dengan menggunakan ‘two roll mill. Kemudian, specimen disediakan bagi

pengujian sifat-sifat mekanikal, iaitu ujian koyakan dan regangan. Keputusan yang

diperolehi menunjukkan kekuatan koyakan dan regangan, serta pemanjangan pada takat

patah menurun dengan penambahan peratusan kandungan sekam padi di dalam koposit

tersebut. Walaubagaimana pun, nilai modulus Young menunjukkan peningkatan bagi

keadaan yang sama. Sementara itu, indek aliran leburan (MFI) bagi komposit kitar

semula RHPE juga diperolehi bagi mendapatkan kesesuaian kelakuan kebolehaliran dan

seterusnya membandingkannya dengan nilai piawai MFI bagi proses pembentuksn haba.

Didapati nilai MFI komposit kitar semula RHPE menurun jika dibandingkan dengan nilai

MFI untuk HDPE tulen, tetapi nilainya masih dalam julat nilai piawai MFI untuk gred

pembentukan haba. Selain itu, analisis termal FTIR dan DSC turut dilakukan bagi

mengkaji sifat komposit kitar semula ini. Analisis FTIR menunjukkan struktur major

kimia dalam komposit RHPE tidak diberi kesan oleh proses kitar semula dan juga

menunjukkan kandungan sekam padi idak mengalami degradasi semasa proses acuan

vii

sunikan. Suhu leburan pula tidak manujukkan perubahan yang ketara jika dibandingkan

dengan komposit RHPE tulen (sebelum kiar semula), justeru itu komposit kitar semula

RHPE tidak banyak mengalami degradasi termal. Maka keadaan sebegini dapat

membuktikan kebolehan komposit kitar semula RHPE diproses semula untuk

aplikasi/kegunaan lain. Daripada ujian yang telah dibuat, komposit kitar semula RHPE

yang mengandungi 40% kandungan sekam padi memberikan sifat-sifat yang bagus

seterusnya menunjukkan kebolehan yang tinggi untuk dibentuk haba.

viii

TABLE OF CONTENT

CHAPTER TITTLE ACKNOWLEDGEMENT iv

ABSTRACT v

ABSTRAK vi

TABLE OF CONTENTS viii

LIST OF TABLES xi

LIST OF FIGURES xii

LIST OF SYMBOLS xv

LIST OF ABBREVIATIONS xvi

LIST OF APPENDIX xvii

1 INTRODUCTION

1.1 Background 1

1.2 Problem Statement 4

1.3 Objectives 5

1.4 Scope of Study 5

2 LITERATURE REVIEW

2.1 Thermoforming Process 7

2.2 Rice Husk 8

2.2.1 Background 9

2.2.2 General Features and Properties 10

2.2.3 Application 11

2.3 Processing of Natural Fiber Polymer 12

ix

3 METHODOLOGY

3.1 Material 23

3.2 Experimental Procedure 25

3.2.1 Samples Preparation 25

3.2.1.1 Grinding 25

3.2.1.2 Two Roll Milling 25

3.3 Material Characterization

3.3.1 Fourier Transform Infra-Red 26

3.3.2 Differential Scanning Calorimetry 27

3.3.3 Melt Flow Index 27

3.4 Material Performance Testing 28

3.4.1 Trouser Tear Resistance 28

3.4.2 Tensile Test 30

3.5 Product Thermoforming 31

4 RESULT & DISCUSSION

4.1 Introduction 32

4.2 Material Characterization 33

4.2.1 Fourier Transform Infra-Red 33

4.2.2 Differential Scanning Calorimetry 36

4.2.3 Melt Flow Index 38

4.3 Material Performing Test 40

4.3.1 Tearing Test 40

4.3.1.1 Tear Strength 40

4.3.2 Tensile Test 42

4.3.2.1 Young’s Modulus 42

4.3.2.2 Tensile Strength 44

4.3.2.3 Elongation at Break 46

4.4 Thermoforming Process 48

x

5 Conclusions and Recommendations

5.1 Conclusion 50

5.2 Recommendations 52

REFERENCES 53

APPENDIX 57

xi

LIST OF TABLES

TABLE NO. TITLE PAGE

1.1 Comparison between natural and glass fiber

(Wambua et. al, 1987) 2

3.1 Composition of rice husk in recycled composite 24

injection grade

3.2 Properties of pure HDPE injection grade (Naurah,2005) 24

3.3 Dimension of specimens Type V 30

4.1 Melting temperature of pure HDPE and recycled RHPE

composite 37

4.2 Mechanical properties of recycled RHPE composite

injection grade 41

xii

LIST OF FIGURES

FIGURE NO. TITLE PAGE

2.1 World rice production figures in 1999 9

(Chaoudhary et al, 2004)

2.2 Effect of rice husk content on mechanical

properties in polypropylene matrix

(Prachayawarakorn and Yaembunying, 2005) 13

2.3 FTIR spectra for (a) polypropylene (b) rice husk

and (c) rice husk-filled polypropylene.


2.4 Elastic modulus vs. filler content for samples

with and without Licocene.

(La Mantia and Morreale, 2006) 17

2.5 Elongation at break vs. filler content for

samples with and without Licocene

(La Mantia and Morreale, 2006) 17

2.6 The effect of OPWF loading on the tensile

and tear strengths of the natural rubber composites

(Ismail and Jaffri, 1999) 22

xiii

2.7 Relationship between the modulus at 100%

elongation (M100) and modulus at 300% elongation

(M300) with OPWF loading

(Ismail and Jaffri, 1999) 22

3.1 Recycled composite milled sheet 26

3.2 Trouser Tear Specimen 29

3.3 Trouser Tear Test 29

4.1 FTIR spectra for pure HDPE and recycled rice

husk-filled HDPE composite. 35

4.2 FTIR spectra for (a) polypropylene (b) rice husk

and (c) rice husk-filled polypropylene.


4.3 Effect of rice husk loading on the melting

point for recycled RHPE composite injection

grade 37

4.4 Effect of rice husk loading on the flow

behavior for recycled RHPE composite injection

grade 39

4.5 Effect of rice husk loading on the tear strength

for recycled RHPE composite injection grade 42

4.6 Effect of rice husk loading on the Young’s

modulus for recycled RHPE composite

injection grade 44

xiv

4.7 Effect of rice husk loading on the tensile strength

for recycled RHPE composite injection grade 46

4.8 Effect of rice husk loading on the elongation

at break for recycled RHPE composite

injection grade 47

4.9 Product from thermoforming process 49

xv

LIST OF SYMBOLS

% - Percentage oC - Degree celcius

N - Newton

MPa - Mega pascal (Pressure)

rpm - Rotor per minutes

s - Seconds

Tm - Melting temperature

Tg - Glass transition temperature

wt % - Weight percentage

xvi

LIST OF ABBREVIATIONS

ABS - Acrylonitrile Butadiene Styrene

ASTM - American Society of Testing Materials

BS - British Standard

CCA - Chromated Copper Arsenate

DSC - Differential Scanning Calorimetry

EVA - Ethylene-Vinyl-Acrylic

FTIR - Fourier Transform Infrared

GSA - Grid Strain Analysis

HDPE - High Density Polyethylene

LTC - Lingnocellulosic-Thermoplastic Composite

MA - Maleic Anyhydride

MFI - Melt Flow Index

OPWF - Oil Palm Wood Flour

PC - Polycarbonate

PE - Polyethylene

PP - Polypropylene

PS - Polystyrene

PVC - Poly (Vinyl Chloride)

RHP - Rice Husk Powder

RHPE - Rice Husk Polyethylene (High Density) composite

SBR - Styrene Butadiene Rubber

SEM - Scanning Electron Microscopy

TGA - Thermogravimertric Analyzer

UF - Urea Formaldehyde

VP - Virgin Pine

xvii

LIST OF APPENDIX

APPENDIX TITLE PAGE

A Working Paper 58

CHAPTER 1

INTRODUCTION

1.1 Background

Composite materials are one of the most advanced engineering materials

today. The addition of high strength fibers to a polymer matrix can greatly improve

thermal and mechanical properties such as ultimate tensile strength, flexural

modulus, and temperature resistance (Herrera-Franco et al.,1996) Composite

materials made from plant fibers are receiving a great deal of attention today since

they are considered an environmentally friendly recourse. This kind of product,

lignocellulosic-thermoplastic composite (LTC) is a combination of any type of

natural fiber or wood waste and polymers, such as PE, PP, PVC in powder or pellet

or regrind, including additives, colourants, lubricants and binders (Naurah, 2005)

2

Fiber reinforced polymeric composite materials are widely used in aerospace

and automotive industries, sports products and medical equipment because of their

low density but high stiffness and strength. In the family of polymers for polymeric

composite materials, thermoplastic resins possess more toughness and better damage

band environmental resistance than thermosetting resins. Additionally, in contrast to

the crosslinkable thermosetting resins with chemical polymerization reactions in the

cure stage, the lack of chemistry in the thermoplastic composite manufacturing

substantially shortens the processing time. As a result, a simple physical process with

heat transfer can process the thermoplastic composite and shaping, making this

composite material suitable for the mass production of composite structures (Hsiao

and Kikuchi, 1999)

On the other hand, composites prepared from glass fibers are widespread

high-performance materials. Glass fibres are the most widely used to reinforce

plastics due to their low cost (compared to aramid and carbon) and good mechanical

properties. However, these fibres have serious drawbacks as indicated in Table 1.1.

The shortcomings have been highly exploited by proponents of natural fibre

composites.

Table 1.1: Comparison between natural and glass fiber (Wambua et. al, 2003)

3

Among all reinforcing fibers, natural fibers have gained their importance

especially for low load bearing applications. Natural fiber reinforced polymer

composites are superior over synthetic fiber reinforced composites in certain

properties like enhanced biodegradability, combustibility, lightweight, ease of

recyclability, etc. These advantages place the natural fibers composites among high

performance composites having economical and environmental advantages, with

good physical properties (Mehta and Parsania, 2006).

It is well known that there are environmental and economical advantages to

produce natural filler/thermoplastic elastomer composites. Cellulosic filler–

reinforced plastics materials are low cost, lightweight, free from health hazards, have

enhanced mechanical properties, and thus have the potential for structural

application. According to one research from Universiti Sains Malaysia that has been

done on Rice Husk Powder (RHP)–Filled Polystyrene/Styrene Butadiene Rubber

(PS-SBR) Blends, the tensile strength decreases with increased RHP loading.

Incorporation of filler in the polymer matrix will reduce the ability of the composites

to transfer applied stress, especially particulate filler of irregular shape. But when

adding the maleic anhydride–polypropylene (MA–PP) as a coupling agent in the

RHP/PS–SBR composites, it improved the interaction between filler and matrix,

causing a more effective transfer of the stresses from matrix to filler, thus increasing

the tensile strength of the composites (Zurina et al., 2004).

4

1.2 Problem Statement

Polymer composites have been a subject of research and utilization for some

decades. During the last years, the increase in environmental concern has become an

important issue as a result, it is also necessary to reduce and rationalize the use of

polymeric materials, not only due to their non-biodegradability, but due to their

production requires large amounts of oil, which is notoriously not renewable. All

these issues have induced researchers to look for alternatives. Thus, the interest

arises toward polymer composites filled with natural organic fillers, especially in

conjunction with recycled and/or recyclable polymer matrices. This class of

composites (sometimes indicated as “green composites”) shows other interesting

features (La Mantia and Morreale, 2006).

Besides, environmental legislation, consumer concern, and waste

management approaches based on concepts like the ‘polluter pays’ are all increasing

the pressure on manufacturers of materials and end-products to consider the

environmental impact of their products at all stages of their life cycle including

ultimate disposal, a ‘cradle to grave’ approach. At this moment, ‘designing for

recycling’ or ‘eco-design’ are becoming a philosophy that is applied to more and

more materials and products. Recycling must be an important part of our daily lives

if we are to preserve the natural resources of our planet.

Although, in theory, all thermoplastic polymers can be remelted and

recompounded into a new grade compound, the presence of certain additives, blends,

or fillers like glass fibers may limit the application area of the recyclate. Therefore,

in this present study, it was my aim to investigate the ability of recycled rice husk-

filled-high density polyethylene composite injection grade to be processed via

thermoforming process, to produce packaging product.

5

1.3 Objectives

The main objective of this research is:

1. To determine the suitability and optimal formulation of recycled HDPE/Rice

Husk (RHPE) composite injection grade for thermoforming process.

This objective is subdivided into:

a) To determine the characteristics and properties of recycled RHPE

composite and analyze its suitability for thermoforming process.

b) To study which composition based on mechanical properties of

recycled RHPE composite could be used for thermoforming process

according to packaging product.

1.4 Scope of Study

1. Samples preparations:

Recycled RHPE composite for thermoforming process.

i) Ground the composites

ii) Melted mix and sheeted by using two roll mills.

2. Materials characterizations

i) Fourier Transform Infra-Red (FTIR)

ii) Differential Scanning Calorimetry (DSC)

iii) Melt Flow Index (MFI)

6

3. Material performing testing

i) Tearing Test

ii) Tensile Test

4. Product thermoforming

Produce thermoformed product by using the optimal formulation of the

composites.

CHAPTER 2

LITERATURE RIVIEW

2.1 Thermoforming Process

Thermoforming is one of the most frequently used thermoplastic sheet-

forming techniques in food packaging because of ease of production, low cost, high

speed and high performance (Ahyan and Zhang, 2000). Polymers that are widely

thermoformed include polyethylene (PE), polypropylene (PP), polystyrene (PS),

polyvinylchloride (PVC), polycarbonate (PC), and acrylonitrile butadiene styrene

(ABS). These materials have difference in their thermoformability that stem from

differences in their mechanical, thermal and rheological properties (Morye, 2005).

Generally, the process consists of heating thermoplastic sheets to their

softening temperatures forcing the hot and flexible material against the contours of a

mould by mechanical, air or vacuum pressure. When held to the shape of the mould

and allowed to cool, the plastic retains the shape and details of the mould. Since the

sheet heats up, it softens and undergoes sag. Excessive sagging causes defect such as

localized thinning, sheet tearing, and webbing.

8

For each type of polymer, there is a different way to thermoform based on the

deformation temperature. Semicrystalline polymers need to be heated closed to their

melting temperature since this type of polymers maintain their rigidity even above

their glass transition temperature (Tg). Meanwhile, amorphous polymers become

sufficiently soft above their Tg and are therefore thermoformed by heating them

above their Tg (McConnell, 1994).

Morye, (2005) noted that, as semicrystalline polymers have a relatively sharp

melting point, the thermoforming temperature window for these polymers is usually

narrow. Also, the melt strength is typically low in semicrystalline polymers at higher

thermoforming temperatures. This causes excessive sagging in many instances.

However, amorphous polymers that are thermoformed above their Tg in the rubbery

plateau typically have a wide thermoforming temperature range due to the large

rubbery plateau region. Amorphous polymers are therefore generally easier to

thermoform than semicrystalline polymers.

2.1 Rice Husk

Rice husk is a waste from agriculture activities and is abundant in Malaysia

and neighboring countries. The present technique of disposing of this material is by

opening burning, which has now become an environmental issue because it

contributes to air pollution. The use of rice husk as a filler in polymer matrices has

become one of the alternative methods for using this waste material and at the same

time overcoming environmental problems. (Zurina et al., 2004)

9

Figure 2.1 World rice production figures in 1999 (Chaoudhary et al., 2004)

2.2.1 Background

The rice grain, commonly called a seed, consists of the true fruit or brown

rice (caryopsis) and the hull, which encloses the brown rice. The hulls are a by-

product of the rice-mills, and are separated from the husked rice through aspiration.

The husks are about one-fifth by weight of the harvested and dried crop, and contain

about 20% silica and the rest being lignin and cellulose (Chaudhary et al., 2004).

Hull is consisting of organic and inorganic component, which 70-80% of hull dry

weight is organic content (Nurhumaiza, 2001). This hull also called as rice husk,

where these materials contribute to environment contamination.

10

Rice husk ash or silica ash, as it is commonly called and referred to

henceforth, is obtained after burning the rice husks and has attracted much attention

in the past decades. It is classified as an industrial waste and depending upon the

combustion conditions, contains approximately 55–97% silica in partly crystalline

and amorphous forms, the rest being an amalgamation of carbon impurity and a

small fraction of metal oxide impurity (Chaudhary et al., 2004).

2.2.2 General Features and Properties

Generally, rice husk is a part of natural fiber source and as natural fibers, they

are relatively abundant in nature and, therefore, can be obtained from renewable

resources. They can also be recycled. The main disadvantages of natural fibres are:

their low permissible processing temperatures, their tendency to form clumps, and

their hydrophilic nature (Torres and Cubillas, 2005).

Rice husk roughly contains 35% cellulose, 35% hemicellulose, 20% lignin and

10% ash (94% silica), by dry weight basis (Prachayawarakorn and Yaembunying,

2005). As a result of much contents of cellulose, rice husk also can be considered as

cellulosic fiber. The cellulosic fiber tends to degrade at about 200°C and quick

become friable with loss of water (Shanks et al, 2004). Besides, these natural fibers

are presence of large amounts of hydroxyl groups, which then make the properties of

rice husk very much in category of hydrophilic.

11

2.2.3 Application

Nowadays, many researchers are interested to study on rice husk as a fiber

composite. Then they are looking to the effect and successful of this kind of fiber

composite as filler in polymer thermoplastic material to reduce the consuming of the

material. This filler is also performed as reinforcement in polymer thermoplastic or

thermosetting to improve their properties. This happened since the cost of polymer

now is now very costly due to the increment of oil price. Rice husk is well referred to

as organic filler.

As a filler, the main cause exist is poor compatibility between hydrophilic

natural fillers and hydrophobic polymers used as matrix. Similar surface tension and

similar polarity of matrix and fillers are required for good interfacial adhesion in

natural filler–reinforced polymer composites. To produce reactive hydroxyl groups

and a rough surface for adhesion with polymeric materials, plant fibers need to

undergo physical and/or chemical treatment to modify the surface structure. The

performance and stability of composite reinforced natural fillers depend on the

development of strong interfacial bonding between fiber and matrix various

composite products such as laminates/panels, doors, roofing sheets, shuttering and

dough moulding compound (Chaudhary et al., 2004)

In addition, the advantages of rice husk used as filler over their traditional

counterparts include relatively low cost, low weight, less damage to processing

equipment, improved surface finish of moulded parts (compared to glass fibre

composites), and good relative mechanical properties (Wambua et al., 2003)

12

2.3 Processing of Natural Fiber Polymer Composites

Many researches had been done in order to improve the thermoplastic

mechanical properties, including blending this polymer with another polymer as well

as with agricultural fibers. These combinations of two or more materials are called

composite. Nowadays, recyclablility of composites also concerned in many research

since the recycling materials in our daily lives is very important consequence to

preserve the natural resources of our planet.

Prachayawarakorn and Yaembunying (2005) did one of the researches that

based on the recylability of composite. They have studied the effect of recycling on

properties of rice husk/polypropylene composite. Rice husk (200 mesh and 40% by

weight) and polypropylene were compounded in a twin-screw extruder and injection

moulding technique was applied in order to obtain testing specimens. It was found

that tensile, flexural strength and % yield elongation of the rice husk-filled

polypropylene were only slightly dropped compared to unfilled polypropylene as

Figure 2.2. The cause in decrease of these properties is due to the immiscibility

between rice husk and polypropylene phase, causing voids or weak point inside the

specimens. Because of the greater stiffness of rice husk than that of polypropylene,

this brings about the improvement in specimen Young's modulus and flexural

modulus that determine stiffness of the specimen. For impact strength, the addition

of rice husk into polypropylene matrix can increase impact strength of the sample

since rice husk can absorb and transfer impact force.

13

0

10

20

30

40

50

60

Mechanical properties

PPPPRH

Tensile strength Flexural strength Elongation at yield

Mpa

Mpa

%

Figure 2.2: Effect of rice husk content on mechanical properties in polypropylene

matrix (Prachayawarakorn and Yaembunying, 2005)

However, when the recycled time of this composite increase, tensile strength,

Young's modulus, flexural strength, flexural modulus and impact strength are found

to be slightly decreased, whereas % elongation at yield seems to be slightly extended.

In general, mechanical behaviour of a polymer is a function of its microstructure or

morphology. The drop in the sample mechanical properties is because the specimens

experience repeated thermal processes, leading to the deterioration of rice husk

component as seen from FTIR spectra (referred Figure 2.3), TGA thermograms and

SEM micrographs. Moreover, enhance in melt flow index (MFI) of the samples was

also obtained when increase the recycled time. Nevertheless, MFI of polypropylene

are greater value than those of the composite specimens. This is attributable to the

rice husk can interrupt the molten polymer to be extruded from the capillary

rheometer (Prachayawarakorn and Yaembunying, 2005).

14

In addition, SEM micrographs revealed the reduction of rice husk particle

size by the recycling process, leading to better phase compatibility between rice husk

and polypropylene. Then, when the rice husk specimen is recycled, % water

absorption of the specimen seems to be reduced with increasing numbers of recycled

times. This is due to the partial removal of cellulose and hemicellulose (as observed

from FTIR and TGA technique), major components in rice husk, bringing about the

reduction of hydrophilicity of rice husk, the main source for absorbing water

(Prachayawarakorn and Yaembunying, 2005).

Figure 2.3: FTIR spectra for (a) polypropylene (b) rice husk and (c) rice husk-filled

polypropylene. (Prachayawarakorn and Yaembunying, 2005)

15

Besides, in different ways of research, Chu and Sullivan (2004) has

investigated about recyclability of a continuous e-glass fiber reinforced

polycarbonate composite. Fiber reinforced plastics are multi-component materials for

which physical properties are strongly dependent on fiber and resin structure. Despite

the disruptive nature of recycling methods on such structures, these materials

nevertheless can be recycled. In this research, they have been studied about the

recyclability of a fiber-reinforced cyclic BPA polycarbonate. It is found that ground

up composite is recyclable and possesses properties as good as or better than a

comparable commercial composite. The processing techniques investigated herein

are injection, extrusion compression, and compression molding. As expected,

processing technique and parameters are important in determining the mechanical

properties of the molded regrind. The results show that injection and extrusion

compression-molding yield recycled composites with good tensile properties, though

the impact strengths are relatively low. This is due to high fiber orientation and fiber

bundle dispersion. On the other hand, compression molded samples, which show

random fiber orientation and low fiber bundles dispersion have relatively low tensile

properties, but excellent impact strength.

Meanwhile, Singleton et al., (2003) were studied on the mechanical

properties, deformation and fracture of a natural fibre/recycled polymer composite. A

composite laminate based on natural flax fibre and recycled high density

polyethylene was manufactured by a hand lay-up and compression moulding

technique. The mechanical properties of the composite were assessed under tensile

and impact loading. Changes in the stress–strain characteristics, of yield stress,

tensile strength, and tensile (Young's) modulus, of ductility and toughness, all as a

function of fibre content were determined experimentally. A significant enhancement

of toughness of the composite was explained in terms of the principal deformation

and failure mechanisms identified by optical microscopy and scanning electron

microscopy. These mechanisms were dominated by delamination cracking, by crack

bridging processes, and by extensive plastic flow of polymer-rich layers and matrix

deformation around fibres. Improvements in strength and stiffness combined with

high toughness can be achieved by varying the fibre volume fraction and controlling

the bonding between layers of the composite.

16

The use of natural organic fillers in addition to post consumer recycled

polymers is getting a growing interest during the last years; this is due to many

advantages they can provide in terms of cost, aesthetic properties, environmental

impact. So, La Mantia and Morreale, (2006) were investigated about the mechanical

properties of recycled polyethylene ecocomposites filled with natural organic fillers.

Several types of wood flour (differing each other with regard to production source

and particle size) were added to a recycled polyethylene coming from films for

greenhouses and the effects of filler type, content, and size were investigated.

Investigation was then focused on the improvement of mechanical properties,

through the addition of polar copolymers (ethylene-co-acrylic acid, ethylene-vinyl

acetate) and a maleic anhydride-grafted-grafted polyethylene in order to try to

overcome the poor adhesion between polar filler particles and nonpolar polymer

chains. Investigation was also based on SEM micrographs. An overall positive

influence of these additives was observed. The addition of organic fillers to post-

consumer recycled polymer matrices causes an increase of elastic modulus (and thus

of rigidity) and of thermo mechanical resistance, while a reduction of ductility is

observed. These effects were more remarkable upon increasing the filler content. The

addition of polar polymers like the EVA copolymer, or the ethylene-co-acrylic acid

copolymer imparted little improvements to the overall properties of the final

composites as shown in Figure 2.4 and 2.5, but slightly lower than expected.

17

Figure 2.4: Elastic modulus vs. filler content for samples with and without

Licocene. (La Mantia and Morreale, 2006)

FIG. 2.5: Elongation at break vs. filler content for samples with and without

Licocene (La Mantia and Morreale, 2006)

18

Moreover, other researches were done by Kamdem et al., (2001). They have

studied on properties of wood plastic composites by compression molding using

particles from virgin pine (VP), recycled urea formaldehyde (UF) bonded (PB) and

recycled chromated copper arsenate (CCA)-treated utility poles retired from services

and virgin and recycled HDPE powder. Wood particles contract from red pine

lumber. The red pine lumber were treated using CCA afterwards removed from

service after 21 years utilization was Wiley milled to wood flour and blended with

recycled high-density polyethylene (HDPE) at 50:50 wood flour-to-plastic weight

ratios in 10 minutes to produce homogenous mixture. The blended materials were

compression molded into panels and the physical and mechanical properties

characterized. Samples containing particles from recycled CCA-treated pine

exhibited flexural bending properties higher than those made with either particle

from virgin pine or recycled urea formaldehyde bonded particleboard. The higher

modulus of elasticity and modulus of rupture from CCA-treated material were

attributed to the increased thermal coefficient of the solid deposits rich in copper

chromium and arsenic present in the cell wall of the recycled CCA-treated wood.

The biological durability and the photo-protection properties were improved for

samples containing recycled CCA-treated wood. The increase in strength properties

was due to the increase in heat diffusion attributed to the presence of copper

chromium and arsenic complexes in the CCA-treated wood.

19

Another research had been carried out by the different researchers;

Bhattacharyya et al., on 2005 that merit attention is that studies of formability

analysis for woodfiber-polypropylene composite sheet retaining their highest

possible aspect ratios. Thermoforming of woodfibre–polypropylene composite sheets

made without any modification of the fibres or the polymer is the focus of this paper,

the emphasis being on their formability and the associated issues. Both the degree to

which a material conforms to the desired part geometry after deformation and the

extent to which a sheet material may be deformed before unacceptable defects occur

are considered. Four thermoforming processes such as V-bending, die-match

forming, air pressure forming and deep drawing have been utilised to examine both

single-curvature and double-curvature deformation conditions. The technique of Grid

Strain Analysis (GSA) has been applied to quantify differences in strain distributions

during sheet deformation.

The effects of thermoforming process parameters and sheet composition on

sheet formability are also discussed. Notably, this study considers composite sheets

reinforced with wood fibres rather than wood flour, enabling the study of fibre lay up

and fibre interlocking effects. While the tensile strengths of the composite sheets

increase marginally, the stiffness increase significantly compared to those of

unreinforced polypropylene. The key deformation mechanism for layered

woodfibre–polypropylene composite sheets is inter-ply shear while intra-ply shear

dominates the deformation of homogeneous sheets. Forming temperature and blank

size have the most pronounced effects on the formability of these composite sheets

(Bhattacharyya et al., 2005)

20

Peterson et al., (2002) were studied on forming performance and

biodegradability of natural fiber polymer composite. A Taguchi approach to

experimental design has been used to analyse the hotpressing and vee-bending of

woodfibre–Biopole composites. Taguchi analysis of the hotpressing process

evidently shows the following manufacturing parameters produce the best tensile

strength and modulus results for this specific study: 210°C platen temperature, 0.5

MPa consolidation pressure, 3 min consolidation time and the application of pressure

once the Biopole melting point (160 °C) has been attained. Analysis of the

hotpressing process clearly shows that platen temperature is the parameter with the

most influence on tensile performance of the composite sheet produced, and

therefore must be most carefully controlled. Notable is the interaction between platen

temperature and consolidation time. Increasing the consolidation time at higher

platen temperatures leads to a significant drop in the tensile performance, which

indicates that a form of thermal degradation might be occurring, in either the fibre or

the polymer itself. Interaction effects also highlight the improved stability of tensile

test results when shorter consolidation times are used.

Meanwhile, in bending (a common manufacturing situation), geometric

conformance is maximised when forming time is 60 s, forming rate is 250 mm/min

and forming radius/thickness ratio is 2 for the composite sheets studied in this paper.

A study of the influence of fibre volume fraction on the biodegradability of these

sheets shows that these composites are highly biodegradable, often degrading at a

rate greater than that of pure Biopole. The results also suggest that a woodfibre mass

fraction of, 15% maximises the degradation of the woodfibre–Biopole. This is

because the woodfibres are believed to act as conduits for the bacteria, thus enabling

greater access and improved degradation rates (Peterson et al., 2002)

21

Different research that has been done by Ismail and Jaffri (1999), were

reported on the physico-mechanical properties of Oil Palm Wood Flour (OPWF)

filled natural rubber composites. The composites were prepared with a laboratory

two roll mill and hot press. Increasing OPWP loading in natural rubber compounds

resulted in reduction of tensile strength, tear strength, and elongation at break but

increased tensile modulus and hardness. The incorporation of OPWF has also

resulted in the reduction of fatigue life. As the filler loading increases, the poor

wetting of the OPWF by the rubber matrix gives rise to poor interfacial adhesion

between the filler and rubber matrix (as evidenced by the scanning electron

microscopy fatigue fracture surface)

As illustrated in Figure 2.6, it shows the effect of OPWF loading on tensile

and tear strength of the composites. Incorporation of filler into a polymer matrix may

increase or decrease the tensile and tear strength of the composites. Unlike fibres,

which have uniform circular cross-section and certain aspect ratios, which normally

improve the strength, the irregular shape of fillers decreases the tensile strength of

the composite due to the inability of the filler to support stresses transferred from

polymer matrix. Also can be seen in Figure 2.7 that the tensile modulus, modulus at

100% elongation (M100) and modulus at 300% elongation (M300) increase with the

increase of filler loading. This observation indicates that the incorporation of OPWF

into the rubber matrix can improve the stiffness of the composites as usually defined

(Ismail and Jaffri, 1999)

22

Fig. 2.6:. The effect of OPWF loading on the tensile and tear strengths of the natural

rubber composites (Ismail and Jaffri, 1999).

Figure 2.7: Relationship between the modulus at 100% elongation (M100) and

modulus at 300% elongation (M300) with OPWF loading (Ismail and Jaffri, 1999).

24

CHAPTER 3

METHODOLOGY

3.1 Material

The raw material that was used in this research was Rice husk- High Density

Polyethylene (RHPE) composites injection grade, where HDPE as a matrix while

rice husk as filler or fiber reinforcement in this composite. This material was

prepared in the project research done by a Master student for injection moulding

process. The compositions of the composites are shows in Table 3.1.

Table 3.1 Composition of rice husk in recycled composite injection grade

Number of Sample

Composition of Rice

Husk (%)

Composition of HDPE

(%)

1 30 70

2 40 60

3 50 50

24

Besides, the properties of pure HDPE injection grade, HD5218AA that produced the

composite was also tabulated in Table 3.2.

Table 3.2 : Properties of Pure HDPE Injection Grade ( Naurah Mat Isa, 2005)

Property Value Unit

Melt Flow Index (2.16kg load) 18 g/10min

Density (annealed) 952 Kg/m2

Tensile Strength at Yield 29 MPa

Elongation at Break 300 %

Flexural Modulus 1050 MPa

Impact Strength (Charpy) 5 kJ/m2

Hardness (Shore D) 65 -

Melting Temperature, Tm 130 °C

Vicat Softening Point (1kg) 123 °C

Thermal Conductivity 0.48 W/m°C

25

3.2 Experimental Procedure

3.2.1 Samples Preparation

3.2.1.1 Grinding

The materials provided, samples of RHPE composites injection grade, were

ground using grinder/crusher machine in the polymer laboratory to form find

particles, so as the next processing stage can be easily performed. The condition of

this process was in room temperature.

3.2.1.2 Two Roll Milling

The crushed recycled composites were mix blended together by means of two

roll mills. The compounding of this composite was set up at 135° C for 7 to 10

minutes excluded 10 minutes of cooling time. This two toll mills has a function to

blend the materials in melt state as well as forming sheet as in Figure 3.1. The

purpose of this melt blending is to ensure the materials are well dispersed and to

homogenize them. The milled sheets were then used for the test samples preparation

for, that are tearing and tensile tests. The amount required to form a sheet were 30

grams.

26

Figure 3.1 Recycled composite milled sheet

3.3 Materials Characterizations

3.3.1 Fourier Transform Infra-Red (FTIR)

The chemical components of pure HDPE injection grade and one of the

compositions of recycled composites were studied by using FTIR spectrometer.

Samples were pressed in thin disc to get the thickness of 10-100 µm for FTIR

measurements. The FTIR spectra were recorded on a Spectrum 2000 GX

spectrometer (Perkin-Elmer) using KBr disc technique for 16 scans. The resolution

was 4 cm-1 and the spectra scanned range was 4000-370 cm-1.

27

3.3.2 Differential Scanning Calorimetry (DSC)

Thermal analysis of the recycled composites was carried out using

Differential Scanning Calorimetry (DSC 7 – Perkin Elmer). The samples were placed

in sealed 10 mg aluminium pans under constant nitrogen flow. DSC was performed

by heating a recycled composite sample of about 5-12 mg from 80 to 160°C. The

heating rate used was at 5 °C/min. The objective from this measurement was to study

the melting points of those composites. Melting temperature, Tm was obtained from

the peak value of the endothermic graph. Thermal analysis results provide process

parameters for thermoforming, and two-roll milling, thus making processing easier;

example processing temperature was predicted from Tm.

3.3.3 Melt Flow Index (MFI)

Melt Flow Rate measures the rate of extrusion of thermoplastics through an

orifice at a prescribed temperature and load. It provides a means of measuring flow

of a melted material that can be used to differentiate grades as with polyethylene, or

determine the extent of degradation of the plastic because of moulding. Degraded

materials would generally flow more as a result of reduced molecular weight, and

could exhibit reduced physical properties.

Approximately 7 grams of the material were loaded or fully loaded into the

barrel of the melt flow apparatus. Melt flow index was performed according to

ASTM D 1238, in melt flow indexer with the temperature of 190°C. The weight of

2.16 kg was applied to a plunger and the molten material was forced through the die.

The extrudate was cut manually referred to Procedure A at the time of 30 sec then it

was weighed. Then, melt flow index was reported as g/10min.

28

3.4 Material Performance Testing

For this section, the performances of materials were studied by doing

mechanical tests, which includes tear and tensile tests. These entire mechanical tests

were carried out according to ASTM. Thus, the optimal composition of recycled

RHPE composite could be determined for producing a good thermoform product.

3.4.1 Trouser Tear Resistance

Tear resistance measures the ultimate force required to tear film or sheet at a

constant tearing speed across a specimen divided by the specimen thickness. It often

used for quality control checks or for material comparison where tear failures are

possible. In addition, this testing is used for films and sheeting with a thickness less

than 1 mm by a single-tear method.

The specimen was cut to the appropriate shape from a sheet. The shape of the

specimen designed as in Figure 3.2 to create a tear when the specimen pulled in

tension. This testing was carried out according to BS2782 Method 360 B, Part 3 by

using a tensile test machine, which is Instron Machine Model 5567. The average

thickness of the specimen was measured for ten test specimens. Then the specimen

was placed in the grips of the testing machine and pulled at a rate of 20 mm per

minute as in Figure 3.3 with 10 N load until rupture.

29

T= 1.5 inch

L= 3 inch

Figure 3.2: Trouser Tear Specimen

Figure 3.3: Trouser Tear Test

30

3.4.2 Tensile Test

The tensile test was performed by elongate a specimen and measuring the

load carried by the specimen. From knowledge of the specimen dimensions, the load

and deflection data could be translated into a stress-strain curve. A variety of tensile

properties could be extracted from the stress-strain curve.

The sheet produced was cut into tensile test samples. The tensile tests were

carried out according to ASTM D-683 Type V on samples were tested at the constant

room temperature (23 ± 2°C). The dimensions of specimen Type V are shown as in

Table 3.3. Ten specimens were tested in unidirections, and then the average of width

and thickness of specimens were measured. Load of 100 N at 5 mm/min were

applied to the specimens. The tensile property measurements (tensile strength,

percent of elongation at yield, and Young’s modulus) from dumbbell specimens were

carried out in a Universal Testing Machine, that is Instron Machine Model 5567.

Table 3.3: Dimensions of specimens Type V

Dimensions Thickness, T, mm (in)

Width of narrow section 3.18 (0.125)

Length of narrow section 9.53 (0.375)

Width overall, min 9.53 (0.375)

Length overall, min 63.5 (2.500)

Gage length 7.62 (0.300)

Distance between grips 25.4 (1.0)

Radius of fillet 12.7 (0.5)

31

3.5 Product Thermoforming

After getting the optimal formulation of recycled RHPE composite based on

the best mechanical properties performance, this composite then were precede for

thermoforming process. This stage of process was done only to prove the capability

of recycled RHPE composite injection grade to be thermoformed to produce product

through thermoforming process.

CHAPTER 4

RESULT AND DISCUSSION

4.1 Introduction

In this research, the samples were studied on for their thermal characteristics

for the pre-determination of the processing parameters as well as melt flow

behaviour for standard thermoform grade range suitability, and the molecular

structure degradation determination. Two mechanical tests, tearing and tensile tests

were carried out to study the performance of the samples for packaging suitability.

The tensile and tear analysis concentrated only on:

1. Tear strength

2. Tensile modulus

3. Tensile strength

4. Elongation at break

33

4.2 Material Characterization

4.2.1 Fourier Transform Infrared

In general, FTIR (Fourier Transform Infrared) Spectroscopy, or simply FTIR

Analysis, is a failure analysis technique that provides information about the

chemical bonding or molecular structure of materials, whether organic or inorganic.

The technique works on the fact that bonds and groups of bonds vibrate at

characteristic frequencies. A molecule that is exposed to infrared rays absorbs

infrared energy at frequencies, which are characteristic to that molecule. During

FTIR analysis, a spot on the specimen is subjected to a modulated IR beam. The

specimen's transmittance and reflectance of the infrared rays at different frequencies

is translated into an IR absorption plot consisting of reverse peaks. The resulting

FTIR spectral pattern then is analyzed and matched with known signatures of

identified materials in the FTIR library.

FTIR spectra of recycled rice husk-filled- HDPE composites injection grade

are presented in Figure 4.1. The spectrum shows the wave numbers in the region of

2600-3100 cm-1 and 1375-1465 cm-1. These wave numbers illustrating the metil

upon saturated hydrocarbon that is produced from C-H stretching of aliphatic

carbon, and CH2 and /or CH3 deformation respectively which present the chemical

group in HDPE molecules. While, peak position also shows the stretching of

aromatic carbon upon C=C at 1529.889 cm-1, 3114.832 cm-1 and 3440.191 cm-1

assigned to O-H stretching of hemicullose and 1705.638 cm-1, which is assigned to

C=O stretching of lignin in rice husk component (Prachayawarankorn and

Yaembunying, 2005).

34

Even the material used in this study was a recycled composite, but it can

retain the existing of rice husk component in the composite. This can be proved by

the comparison between the FTIR analysis of recycled RHPE composite and rice

husk-filled polypropylene as in Figure 4.2 (c). It clearly shows the vibrational bands

of compositions from rice husk that presents the wave numbers in region of 3250-

3500 cm-1, 1700-1750 cm-1 and 1400-1600 cm-1 with respect to hemicellulose,

lignin and aromatic carbon stretching.

Therefore, it indicates that the major chemical structure of rice husk filled in

HDPE samples is not affected by recycling process. It also shows the rice husk

contents was not undergo degradation during the injection moulding process, as well

as not formed thermoset composite product. As a result, this shows the ability of

recycled RHPE composite can be reprocessed or recompounded into other grade

compound/product.

35

Figure 4.1: FTIR spectra for pure HDPE and recycled rice husk-filled HDPE

composite.

Figure 4.2: FTIR spectra for (a) polypropylene (b) rice husk and (c) rice husk-filled

polypropylene. (Prachayawarakorn and Yaembunying, 2005)

36

4.2.2 Differential Scanning Calorimetry Analysis

The change of the melting point of the polymers is due to the incorporation of

fibers (Manikandan et al., 1996). The DSC results are summarized in Table 4.1 as

the melting temperature of the materials used. The comparison between the various

percentage of rice husk in the recycled RHPE composite injection grade are

illustrated in Figure 4.3. During the DSC heating scan, the recycled RHPE

composites injection grade show only one endothermic peak that occurred in the

melting region. Thus the peak indicates the melting temperature, Tm of the materials.

The melting temperature of pure HDPE injection grade was found to be

130°C (Naurah, 2005). The incorporation of 30%, 40%, and 50% of rice husk

contents in that composite had reduced the Tm of pure HDPE to 128°C, 127°C and

125°C respectively. It can be seen that Tm of pure HDPE was depressed by about 2-

5°C by the addition of certain percentages of rice husk. The addition of rice husk in

HDPE lowered the Tm of HDPE and shifted to further lower temperatures when the

amount of rice husk contents was increased. However, for the curve of RH40PE,

there are two peaks observed. The second peak occurs may be due to the presences

of impurity during the samples preparation or high molecular weight HDPE. This is

possible because the temperature range over which a mixture of compounds melts is

dependent on their relative amounts, consequently, will broadened the melting.

Since temperature does not differ much from the pure RHPE therefore

recycled RHPE does not undergo much thermal degradation, thus can be reprocessed

for other usage. The predetermined Tm for the thermoform processed parameter

using recycled RHPE are 128.16 ◦C, 127.16 ◦C and 125.95 ◦C with respect to 30%, 40

%, 50 % rice husk contents.

37

Table 4.1: Melting temperature of pure HDPE and recycled RHPE composites

Figure 4.3: Effect of rice husk loading on the melting point for recycled RHPE

composite injection grade.

Material

Melting Temperature, Tm (°C)

Pure HDPE injection grade

130.03

Recycled RH30PE composite

128.16


127.95


125.95

38

4.2.3 Melt Flow Index

Melt flow index values of pure HDPE injection grade and various

compositions of rice husk contents in recycled RHPE composite injection grade are

shown in Figure 4.4. It can be seen that the melt flow index of pure HDPE injection

grade gave greater value than other recycled RHPE composites injection grade. As

the rice husk content increases, the MFI value decreases for all composites. This is

expected since the addition of fillers or fibers i.e rice husk to the HDPE restricts

molecular motion, imposing extra resistance to flow (Ahmad Fuad et al., 1997).

While, according to Prachayawarakorn and Yaembunying, (2005), the lower MFI

value is due to the interruption of rice husk particle in the molten polymer to be

extrudate from the capillary rheometer.

The molecular structure of samples composites has an influence on its

properties and processing characteristics. The MFI value gives a rough indication of

molecular weight or chain length. A material with a high melt index has shorter

chains and a lower molecular weight or smaller molecules, and vice versa. This

corresponds to the general deterioration in physical properties such as melt viscosity,

heat softening point, tensile strength at rupture and others, as the MFI increases or

decrease. Therefore, the lower MFI value indicates that greater melt viscosity in the

filled samples. The usual trend of decreasing melt index values to filler content is

reversed and the melt index actually increases with filler contents. While, the

observation shown that resin degradation is expected to result in lowering the

molecular weight, easing material flow and thus higher MFI values (Ahmad Fuad et

al., 1997).

According to Bruins, the range of MFI value for the standard thermoform

grade is 2-10 g/10 min. Therefore, from this MFI analysis, only recycled RHPE

composite with 40 % and 50 % rice husk contents were fell in this standard MFI

values. So, these recycled composite have show their suitability to be thermoformed.

39

0

2

4

6

8

10

12

14

16

18

20

0 30 40 50

Percentage of Rice Husk (%)

MFI

Val

ue (g

/10m

in)

Figure 4.4: Effect of rice husk loading on the flow behavior for recycled RHPE


40

4.3 Material Performing Test

4.3.1 Tearing Test

4.3.1.1 Tear Strength

` In tearing test, the most important property that would be considered is tear

strength. The tear strength is a measure of the resistance of a material to tear forces.

Tear resistance involve a predominantly effect by interfacial bonding in flexible

composite. As in impact resistance testing, where area under the stress-strain curve is

proportional to toughness or the energy to fracture the specimen, tear resistance is a

measure of crack or slit propagation (Harry and John, 1988). While, according Dilara

and Briassoulis (1998), tear resistance of plastic films is a complex function of its

ultimate resistance to rupture. Tear resistance of plastic films is very important with

regard to their overall mechanical behavior and a common failure mechanism for

agricultural plastic films.

Table 4.2 shows the mechanical properties of recycled RHPE composites

injection grade. While, Figure 4.5 shows effect of rice husk loading on the tear

strength for recycled RHPE composite injection grade. Incorporation of filler into a

polymer matrix may increase or decrease the tear strength of the composites.

Referring to Figure 4.5, the tear strength was decreased with the increase in the

percentage of rice husk filled in the composites. The decreased tear strength of the

composite was due to the inability of the filler to support stresses transferred from

polymer matrix.

41

This has been attributed to the incapability of rice husk fibers to dissipate

stress through the shear yield prior to fracture, and they hindered the local chain

motions of the HDPE molecules that enable the matrix shear yield. Since the fiber-

matrix, interfacial strength is too low, poor stress will then occurs and a weak

composite were resulted. Then, it decreases the ability of composite to resist the

stress during slit propagation (Nurfatimah, 2006).

Based on research by Ismail and Jaffri, 1999, the maximum tear strength for

film composite is 20 N/mm. Therefore, when this value is compared with tear

strength of the recycled RHPE composite, it shows that the suitability of recycled

RHPE composite to be used as thermoform packaging product.

Table 4.2: Mechanical properties of recycled RHPE composites injection grade

Samples

RH30PE

RH40PE

RH50PE

Tear strength

(N\mm)

5.5064 ± 0.41

4.6244 ± 0.08

3.8051 ± 0.09

Young’s

modulus (GPa)

1.232 ± 0.98

2.347 ± 0.83

1.842 ± 1.11

Tensile

strength (MPa)

16.258 ± 0.98

13.9211 ± 0.83

10.4289 ± 1.11

Elongation at

break (%)

7.5046 ± 0.21

4.9914 ± 0.37

4.1846 ± 0.74

42

0

1

2

3

4

5

6

7

20 30 40 50 60

Percent of Rice Husk Contents, (%)

Tea

r St

reng

th, (

N/m

m)

Figure 4.5: Effect of rice husk loading on the tear strength for recycled RHPE


4.3.2 Tensile Test

4.3.2.1 Young Modulus

As expected, the modulus, which indicates materials stiffness, increases

steadily with addition of rice husk contents in the composites, but it slightly dropped

when 50% filled the fibers as shown in Figure 4.6. Because of the greater stiffness of

rice husk than that HDPE, this brings about the improvements in specimen Young’s

modulus that determine stiffness of the specimen (Prachayawarankorn and

Yaembunying, 2005). In other words, rice husk itself has a higher Young’s modulus

compared with HDPE. This reflects the increase of brittleness of the materials

(Hattotuwa et al., 2002).

43

In general, mechanical behavior of a polymer is a function of its

microstructure or morphology (Prachayawarankorn and Yaembunying, 2005).

Fibrous or fiber filler work by having a given stress transferred through the polymer

matrix medium to the dispersed fiber themselves, which have greater strength

stability properties than the polymer medium itself. This is the reason how the filler

increase the modulus of polymer (Azman Hassan). However, for the decreasing

modulus when added with 50% of rice husk is due to the immiscibility between rice

husk and HDPE phase, and tendency to agglomerate within themselves, causing

voids or weak point inside the specimens. Thus, it contributes to weak interfacial

adhesion with polymer matrix (Herrera-Franco et al., 1997).

On the other hand, seem the material used were recycled composite, may be

the Young’s modulus of this recycled composite are slightly decrease upon the

recycling process. This due to the reduction of particles sizes of rice husk fibers upon

recycling then gives effect on the fiber aspect ratio. Nevertheless, although the fibers

have a low aspect ratio, they are able to impart a significant improvement in stiffness

by hindering the movement of HDPE molecules (Abu Bakar et al., 2005).

Based on the research, that had done by Peterson et al. 2002, the maximum

tensile modulus of composite film for thermoforming property analysis is 3.5 GPa.

Therefore, the tensile modulus obtained for the recycled RHPE composites from this

study were satisfied the requirement of the composite film for thermoforming

process. This shows that the recycled RHPE composite were suitable to be used as

thermoform packaging product.

44

0

0.5

1

1.5

2

2.5

3

20 30 40 50 60

Percent of Rice Husk Content, (%)

Youn

g's

Mod

ulus

, (G

Pa)

Figure 4.6: Effect of rice husk loading on the Young’s modulus for recycled RHPE


4.3.2.2 Tensile Strength

In the recycled RHPE composites injection grade, the incorporation

between rice husk and HDPE was found to gradually decrease in tensile strength

with additional rice husk content as shown in Figure 4.7. According to Ismail and

Azahari, 2002, this happened due to the immiscibility between rice husk and high-

density polyethylene phases, causing voids or weak points inside the specimens.

Then it is also revealed that no reinforcement be obtained by the addition of filler,

and possible agglomeration, which weaken the stress transfer from matrix to filler.

45

The agglomeration of the fibers may be due to the relatively weak interaction

between fibers and matrix, compared to the strong fiber-fiber interaction caused by

hydrogen bonding. Therefore, fibers have tendency to agglomerate among

themselves into fiber bundles, which consequently lower the area of contact with the

matrix. These fibers tend to cling together in bundles and to resist dispersion as the

fiber content increase (Abu Bakar et al., 2005)

In addition, in accordance with Abu Bakar et al., 2005, the weakened fiber-

matrix interface become potential sites for crack growth because of the inability of

fibers to support the stress transfer to the polymer matrix. Voids in the matrix may

als become site for cracking initiation. So, without having time to strain enough,

these composite were already tended to rupture. La Mantia and Morreale , 2006,

have found that, the decrease of tensile strength is related to the increase of fragility

or brittleness of the samples. This also highlighted by the decrease of elongation at

break. The fact that rigidity, which is quantified by Young’s modulus of the samples,

filled with rice husk is slightly higher.

From this study, this recycled composite has shown the suitability to be

thermoformed into packaging product. This packaging product usually is made up

from plastic film. Based one research, written by Antonio and Macros, 2003, the

maximum tensile strength for plastic film based recycled composite is 25 MPa.

Therefore, when this value is compared with tensile strength of the recycled RHPE

composite, it shows that the suitability of recycled RHPE composite to be used as


46

4

6

8

10

12

14

16

18

20 30 40 50 60


Ten

sile

Str

engt

h, (M

Pa)

Figure 4.7: Effect of rice husk loading on the tensile strength for recycled RHPE


4.3.2.3 Elongation at Break

Other properties can be discussed in tensile properties is elongation at break

of the composites. This elongation at break were measured the elongation at the

moment of rupture of the test specimens. As we can see in Figure 4.8, the elongation

at break of the composites is gradually decreased correspond to the increased in rice

husk loading. Same reason as tensile strength property, that is due to the

immiscibility between rice husk and HDPE phases, resulting voids or weak point,

inside the specimens (Prachayawarankorn and Yaembunying, 2005).

47

Besides, the decline in elongation at break may be due to the reduction of

extensible matrix in the composites with increasing filler content. Moreover, the

filler particles have created the resistance for the matrix molecules to deform upon

the elongation of the specimens (Ismail and Azahari, 2002). This occurrence has

been proven during the testing of the composite’s melt flow behavior. Referred back

to Figure 4.4, as the filler filled composites increase, the melt flow was decreased

which is due to the interruption of rice husk particle in the molten polymer. This is

also reported by Ismail and Jaffri, in 1999 that the decreasing of elongation at break

with addition of more filler to the polymer matrix. With increasing in filler loading,

the stiffness and brittleness of the composite increase gradually with associated

decrease in the elongation at break.

Theoretically, the stress whitening occurs almost immediately on elongation

of composites containing high filler concentration, or the filler consist of large

particles. In both cases, the matrix is restricted in its ability to stretch between

particles or around larger particles and debonding of the particles causes cavitation

that appears as stress whitening. Smaller particles at the low concentration are free to

move with the matrix, and correspondingly, the matrix is free to stretch around them.

However, very weak interfacial bonding causes almost intermediate separation of the

matrix from the particles, and cavitations begin at low elongation (Harry and John).

Meanwhile, according to Malpas and Kemphorn, 1986, the limitation value of

elongation at break of filled HDPE for thermoform properties is 22 ± 2 %. From this

study, the recycled composites have shown the suitability to be thermoformed into

packaging product as the result obtained were not exceed the maximum value. Then,

these recycled RHPE composites have the ability to be reprocessed into the

thermoform grade product.

48

0

1

2

3

4

5

6

7

8

9

10

30 40 50

Percentage of rice husk content, (%)

Elo

ngat

ion

at b

reak

, (%

)

Figure 4.8: Effect of rice husk loading on the elongation at break for recycled RHPE


4.4 Thermoforming Process

From the material characterizations and mechanical testing above, recycled

RHPE composite with 40% rice husk contents was considered as the suitability and

optimal formulation of recycled RHPE composite injection grade for thermoforming

process. Therefore, to prove this concern, the sample of sheet from two-roll milling

was used in compression moulding process (also known as hot press) to produce a

thin film composite. The film was then thermoformed at 123 °C based on the

predetermined temperature of recycled RHPE composite filled with 40 % of rice

husk. The duration of this process was within 10 minutes under 2 bar. The product

developed as in Figure 4.9.

49

Figure 4.9: Product from thermoforming process

CHAPTER 5

CONCLUSIONS AND RECOMMENDATIONS

5.1 Conclusions

Recycled RHPE composite injection grade contained different percentages of

rice husk have been studied on the capability to be processed using thermoforming

technique. The result in this present study showed that a useful recycled composite

injection grade with good properties could be successfully recompounded into a

thermoforming grade. Several conclusions can be made from this study regarding to

the effect of fiber contents to the mechanical properties which are tear and tensile

properties.

The incorporation of the rice husk into HDPE matrix has resulted in the

improvement in the tensile modulus or Young’s modulus, but it caused decrement in

tensile strength and elongation at break, with additional of rice husk contents. This is

due to the greater stiffness of rice husk than that HDPE, that result in the

improvements in specimen Young’s modulus thus determine stiffness of the

specimen.

51

However, the immiscibility between rice husk and high-density polyethylene

phases, causing voids or weak points inside the specimens result in the decreased in

tensile strength and elongation at break. It is also observed that no reinforcement is

obtained by the addition of filler, only possible agglomeration, which weaken the

stress transfer from matrix to filler. This effect also related to the increase in fragility

or brittleness of the samples. , The filler particles have created the resistance for the

matrix molecules to deform upon the elongation of the specimens, which has been

proven with the composite’s melt flow behavior i.e. MFI test.

The same situation also occurred on tearing properties. The tear strength was

decreased with the increases the percentage of rice husk filled in the composites. The

decreased in tear strength of the composite due to the inability of the filler to support

stresses transferred from polymer matrix. This has been attributed to the incapability

of rice husk fibers to dissipate stress through the shear yield prior to fracture, and

they hindered the local chain motions of the HDPE molecules that enable the matrix

shear yield. If the fiber-matrix interfacial strength is too low, poor stress will then

occurs and a weak composite were resulted. Then, it decreases the ability of

composite to resist the stress during slit propagation.

The overall results from this study shows that the mechanical properties of

recycled RHPE composites injection grade were strongly affected by the rice husk

contents thus effect the interfacial adhesion between fibers-matrix phases. However,

the best formulation that can be thermoformed based on the optimum value of

modulus and strength of the composites are gave by the recycled RHPE composites

contained 40% rice husk.

52

From the result obtained, there is several factors influence the suitability of

this recycled RHPE composite to be thermoformed. This can be found from the

analysis of FTIR, DSC and also MFI. The rice husk contents was not undergo

degradation and thermal degradation during the injection moulding process, as well

as not formed thermoset composite product. Besides, MFI value of recycled RHPE

composite also found fall within the range of MFI value for the standard

thermoform grade that is between 2-10 g/10 min. Moreover, it also found that, the

mechanical properties of this recycled RHPE composite were fulfilling the

requirements of thermoform material grade. This shows the suitability of recycled

RHPE composite can be reprocessed or recompounded into thermoforming grade

compound/product.

5.2 Recommendations

There are a few approaches, which may be used to improve the weakness in this

research study. The suggestions are:

1. Recycled RHPE composite has to use a coupling agent to get better in

mechanical properties. This formulation will be achieved in good dispersion

and wetting of the fibers in the matrix, then giving rise to a strong interfacial

adhesion.

2. Further study on thermoforming process that need to be carried out on the

determination of the optimum operating condition which are forming

temperature, air forming pressure and heating time onto the thermoformed

recycled RHPE composites injection grade.

53

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Antonio, F.A., and Macros, V.D. (2003). A Mechanical Analysis on Recycled

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Bhattacharyya, D., Bowis, M. and Jayaraman, K., (2005). Thermoforming

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Chaudhary, D.S., Jollands, M.C. and Cser F., (2004). Recycling Rice Hull: A Filler

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Chu, J and Sullivan, J.L. (2004). Recyclability of a Continuous E- Glass Fiber

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Hattotuwa, G.B.P., Ismail, H. and Baharin Azahari (2002). Tensile Properties of Rice

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Kamden, D.P., Jiang, H., Cui W., Freed J. and Matuana L.M., (2004). Properties of

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57

APPENDIX

APPENDIX A

PERFORMANCE OF RECYCLED HIGH DENSITY POLYETHYLENE (HDPE)/

RICE HUSK COMPOSITE INJECTION GRADE FOR THERMOFORMING

PROCESS

Fatimah Zaharah, C.M., Wan Aizan, W.A.R.

Polymer Engineering Department,Faculty of Chemical and Natural Resources

Engineering, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor, Malaysia

ABSTRACT All thermoplastic polymers can be remelted and recompounded into a new

grade, but the presence of certain additives, blends, or fillers like glass fibers may limit

the application area of the recyclate. In this present study, it was my aim to investigate

the ability of recycled rice husk-filled-high density polyethylene (RHPE) composite

injection grade to be processed using thermoforming technique. Various recycled RHPE

composite injection grade, that is with composition 30%, 40% and 50% of rice husk were

investigated in this study. These composites were first grinded to a fine form using

laboratory grinder machine before being melt-blended and milled into sheets on a two-

roll mill. Then, test specimens were prepared to study on the mechanical properties that is

tearing test and tensile test. The results showed the tear and tensile strength were reduced

significantly with the percentage increase of rice husk contents. However, the Young

modulus had increased. MFI was found to decrease as compared to the virgin HDPE, but

is within the standard MFI for thermoforming material grade. FTIR spectroscopy and

DSC thermal analysis used to characterize the recycled composite materials. Recycled

RHPE composites containing 40% rice husk exhibit good properties and showed high

capability to be thermoformed.

Keywords: Rice husk; HDPE; recycled composite; processing grade; thermoforming

1.0 Introduction

Polymer composites have been subjected to increasing interest, study, and

utilization for some decades. During the last years, however, the increase in

environmental concern has pointed out how it is also necessary to reduce and rationalize

the use of polymeric materials, not only due to their non-biodegradability, but due to their

production requires large amounts of oil, which is notoriously not renewable. All these

issues have induced to look for alternatives. Thus, the interest arises toward polymer

composites filled with natural organic fillers, especially in conjunction with recycled

and/or recyclable polymer matrices. This class of composites (sometimes indicated as

“green composites”) shows other interesting features [5].

Besides, environmental legislation, consumer concern, and waste management

approaches based on concepts like the ‘polluter pays’ are all increasing the pressure on

manufacturers of materials and end-products to consider the environmental impact of

their products at all stages of their life cycle including ultimate disposal, a ‘cradle to

grave’ approach. At this moment, ‘designing for recycling’ or ‘eco-design’ are becoming

a philosophy that is applied to more and more materials and products. Recycling must be

an important part of our daily lives if we are to preserve the natural resources of our

planet.

Although, in theory, all thermoplastic polymers can be remelted and

recompounded into a new grade, the presence of certain additives, blends, or fillers like

glass fibers may limit the application area of the recyclate. Therefore, in this present

study, it was intended to investigate the ability of recycled rice husk-filled-high density

polyethylene composite injection grade to be processed by thermoforming process, which

is produced packaging product.

2.0 Methods

2.1 Materials

The raw materials that were been used in this research are Rice husk- High

Density Polyethylene (RHPE) composites injection grade, where HDPE as a matrix while

rice husk as filler or fiber reinforcement in this composite. There were three compositions

of the composites had been used, 30%, 40% and 50% of rice husk contents.

2.2 Sample preparations

The materials provided, which are the samples of RHPE composites injection

grade were ground using grinder/crusher machine in the polymer laboratory to form find

particles. These find/small particles would make the next processing easy to perform. The

condition of this process was in room temperature. Then, the crushed recycled

composites were mix blended together by means of two roll mills. The compounding of

this composite was set up at 135° C for 7 to 10 minutes excluded 10 minutes of cooling

time. This two toll mills has a function to mix blending the materials in melt state as well

as it would form a sheet as in Figure 3.1. The purpose of this melt blending is to ensure

the materials are well dispersed and to homogenize them. The milled sheets were then

used for the preparation for samples testing, that are tearing and tensile test. The amounts

of these materials to form a sheet were 30 grams.

2.3 Material characterizations

The chemical components of samples pure HDPE injection grade and one of the

compositions of recycled composites were studied by using FTIR spectrometer. Then,

samples were pressed in thin disc to get the thickness of 10-100 µm for FTIR

measurements. The FTIR spectra were recorded on a Spectrum 2000 GX spectrometer

(Perkin-Elmer) using KBr disc technique for 16scans. The resolution was 4cm-1 and the

spectra scanned range was 4000-370 cm-1.

Then, thermal analysis of the materials that is recycled composites was carried out

using Differential Scanning Calorimetry (DSC 7 – Perkin Elmer). The samples were

placed in sealed 10 mg aluminium pans under constant nitrogen flow. DSC was

performed by heating a recycled composite sample of about 5-12mg from 80 to 160°C.

The heating rate was used at 5 °C/min. The objective from this measurement was to study

the melting points of those composites.

Melt flow index was performed according to ASTM D 1238, in melt flow indexer

with the temperature of 190°C. The weight of 2.16kg was applied to a plunger and the

molten material was forced through the die. The extrudate was cut manually referred to

Procedure A at the time of 30sec then it was weighed. Then, melt flow index was

reported as g/10min.

2.4 Material Performance Test

For this section, the performances of materials were studied by doing mechanical

tests, which includes tear and tensile tests. Thus, the optimal composition of recycled

RHPE composite could be determined for producing a good thermoform product. For

tearing test, the specimen was cut to the appropriate shape from a sheet (trousers shape)

to create a tear when the specimen pulled in tension. This testing was carried out

according to BS2782 Method 360 B, Part 3 by using a tensile test machine, which is

Instron Machine Model 5567. The average thickness of the specimen was measured for

ten test specimens. Then the specimen was placed in the grips of the testing machine and

pulled at a rate of 20 mm per minute with 10 N load until rupture. Then the tensile test

was performed by elongate a specimen and measuring the load carried by the specimen.

The sheet produced was cut into tensile test samples. The tensile tests were carried out

according to ASTM D-683 Type V on samples were tested at the constant room

temperature (23 ± 2°C). Load of 100 N at 5mm/min were applied to the specimens. The

tensile property measurements were carried out in a Universal Testing Machine, that is

Instron Machine Model 5567.

2.5 Product Thermoforming

After getting the optimal formulation of recycled RHPE composite based on the

best mechanical properties performance, this composite then were precede for

thermoforming process. This stage of process was done only to prove the capable of

recycled RHPE composite injection grade could be thermoformed to produce product

through thermoforming process.

3.0 Results and discussion

3.1 Material Characterizations

FTIR spectra of recycled rice husk-filled- HDPE composites injection grade are

presented in Figure 1. The spectrum shows the wave numbers in the region of 2600-3100

cm-1 and 1375-1465 cm-1. These wave numbers illustrating the metil upon saturated

hydrocarbon that is produced from C-H stretching of aliphatic carbon, and CH2 and /or

CH3 deformation respectively which present the chemical group in HDPE molecules.

While, peak position also shows the stretching of aromatic carbon upon C=C at

1529.889 cm-1, 3114.832 cm-1 and 3440.191 cm-1 assigned to O-H stretching of

hemicullose and 1705.638 cm-1, which is assigned to C=O stretching of lignin in rice

husk component (Prachayawarankorn and Yaembunying, 2005).

Even the material used in this study was a recycled composite, but it can retain

the existing of rice husk component in the composite. Therefore, it indicates that the

major chemical structure of rice husk filled in HDPE samples is not affected by

recycling process. It also shows the rice husk contents was not undergo degradation

during the injection moulding process, as well as not formed thermoset composite

product. As a result, this shows the ability of recycled RHPE composite can be

reprocessed or recompounded into other grade compound/product.

Fig. 1. FTIR spectra for pure HDPE and recycled rice husk-filled HDPE

composite

From the DCS analysis, the results are summarized as the melting temperature of

the materials used. The comparison between the vary percentage of rice husk in the

recycled RHPE composite injection grade are illustrated in Figure 2. The melting

temperature of pure HDPE injection grade was found to be 130°C [5]. The incorporation

of 30%, 40%, and 50% of rice husk contents in that composite were reduced the Tm of

pure HDPE to 128°C, 127°C and 125°C respectively. It can be seen that Tm of pure

HDPE was depressed by about 2-5°C by addition of percentage of rice husk contents.

The addition of rice husk in HDPE lowered the Tm of HDPE and shifted to further lower

temperatures when the amount of rice husk contents was increased. However, for the

curve of RH40PE, there is shows two peaks. The second peak occurs may be due to the

presences of impurity during the samples preparation. The impurity might be the pure

HDPE materials that were not mixed well during the process. Therefore, it also gave the

thermal reading upon the DSC analysis at around 130°C.

0

5

10

15

20

0 30 40 50

Percentage of Rice Husk (%)

MFI

Val

ue (g

/10m

in)

Fig. 2. Effect of rice husk loading on

the melting point for recycled RHPE


Fig 3. Effect of rice husk loading on the

flow behavior for recycled RHPE


Since temperature does not differ much from the pure RHPE therefore recycled

RHPE does not undergo much thermal degradation, thus can be reprocessed for other

usage. The predetermined Tm for the thermoform processed parameter using recycled

RHPE are 128.16 ◦C, 127.16 ◦C and 125.95 ◦C with respect to 30%, 40 %, 50 % rice husk

contents.

Melt flow index values of pure HDPE injection grade and varies compositions of

rice husk contents in recycled RHPE composite injection grade are shown as in Figure 3.

It can be seen that the melt flow index of pure HDPE injection grade gave greater value

than others recycled RHPE composites injection grade. As the rice husk content

increases, the MFI value decreases for all composites. This is an expected event as

addition of fillers or fibers i.e rice husk to the HDPE restricts molecular motion, imposing

extra resistance to flow [1]. While, according to [7] the lower MFI value is due to the

interruption of rice husk particle in the molten polymer to be extrudate from the capillary

rheometer.

The molecular structure of samples composites has an influence on its properties

and processing characteristics. The MFI value gives a rough indication of molecular

weight or chain length. A material with a high melt index has shorter chains and a lower

molecular weight or smaller molecules, and vice versa. This corresponds to the general

deterioration in physical properties such as melt viscosity, heat softening point, tensile

strength at rupture and others, as the MFI increases or decrease. Therefore, the lower MFI

value indicates that greater melt viscosity in the filled samples.

3.2 Material Performing Test

Table 1 shows the mechanical properties of recycled RHPE composites injection

grade. While, Figure 4 shows effect of rice husk loading on the tear strength for recycled

RHPE composite injection grade. Incorporation of filler into a polymer matrix may

increase or decrease the tear strength of the composites. Referred to Figure 4, the tear

strength was decreased with the increases the percentage of rice husk filled in the

composites. The decreases tear strength of the composite due to the inability of the filler

to support stresses transferred from polymer matrix.

This has been attributed to the incapable of rice husk fibers to dissipate stress

through the shear yield prior to fracture, and they hindered the local chain motions of the

HDPE molecules that enable the matrix shear yield. Since the fiber-matrix, interfacial

strength is too low, poor stress will then occurs and a weak composite were resulted.

Then, it decreases the ability of composite to resist the stress during slit propagation [8].

Table 1: Mechanical properties of recycled RHPE composites injection grade

Samples

RH30PE

RH40PE

RH50PE

Tear strength

(N\mm)

5.5064 ± 0.41

4.6244 ± 0.08

3.8051 ± 0.09

Young’s

modulus (GPa)

1.232 ± 0.98

2.347 ± 0.83

1.842 ± 1.11

Tensile

strength (MPa)

16.258 ± 0.98

13.9211 ± 0.83

10.4289 ± 1.11

Elongation at

break (%)

7.5046 ± 0.21

4.9914 ± 0.37

4.1846 ± 0.74

0

1

2

3

4

5

6

7

20 30 40 50 60


Tea

r St

reng

th, (

N/m

m)

Fig. 4. Effect of rice husk loading on tear strength for recycled

RHPE composite injection grade.

Besides, the modulus, which indicates materials stiffness, increases steadily with

addition of rice husk contents in the composites, but it slightly dropped when 50% filled

the fibers as shown in Figure 5. Because of the greater stiffness of rice husk than that

HDPE, this brings about the improvements in specimen Young’s modulus that determine

stiffness of the specimen [10]. In other words, rice husk itself has a higher Young’s

modulus compared with HDPE. This reflects the increase of brittleness of the materials

[3],

However, for the decreasing modulus when added with 50% of rice husk is due to

the immiscibility between rice husk and HDPE phase, and tendency to agglomerate

within themselves, causing voids or weak point inside the specimens. Thus, it contributes

to weak interfacial adhesion with polymer matrix [4].

Based on the research [9], the maximum tensile modulus of composite film for

thermoforming property analysis is 3.5 GPa. Therefore, the tensile modulus obtained for

the recycled RHPE composites from this study were satisfied the requirement of the

composite film for thermoforming process. This shows that the recycled RHPE

composite were suitable to be used as thermoform packaging product.

0

50000

100000

150000

200000

250000

20 30 40 50 60

Percent of Rice Husk Content, (%)

You

ng's

Mod

ulus

, (M

Pa)

Fig 5. Effect of rice husk loading on the

Young’s modulus for recycled RHPE


4

6

8

10

12

14

16

18

20 30 40 50 60


Ten

sile

Str

engt

h, (M

Pa)

Fig. 6. Effect of rice husk loading on the

tensile strength for recycled RHPE


In the recycled RHPE composites injection grade, the incorporation between rice

husk and HDPE was found to gradually decrease in tensile strength with additional rice

husk content as shown in Figure 6. According to [3], this happened due to the

immiscibility between rice husk and high-density polyethylene phases, causing voids or

weak points inside the specimens. Then it is also revealed that no reinforcement be

obtained by the addition of filler, and possible agglomeration, which weaken the stress

transfer from matrix to filler.[5], have found that, the decrease of tensile strength is

related to the increase of fragility or brittleness of the samples.

The maximum tensile strength for plastic film based recycled composite is 25

MPa [2]. Therefore, when this value is compared with tensile strength of the recycled

RHPE composite, it shows that the suitability of recycled RHPE composite to be used as


Other properties can be discussed in tensile properties is elongation at break of the

composites. This properties were measured the elongation at the moment of rupture of the

test specimens. As we can see in Figure7, the elongation at break of the composites are

gradually decrease correspond to the adding up the rice husk loading. Same reason as

tensile strength property, that is due to the immiscibility between rice husk and HDPE

phases, resulting voids or weak point, inside the specimens [10].

Besides, the decline in elongation at break may be due to the reduction of

extensible matrix in the composites with increase of filler content. Moreover, the filler

particles have created the resistance for the matrix molecules to deform upon the

elongation of the specimens [3]. This occurrence has been proven during the testing of

the composite’s melt flow behavior. Referred back to Figure 4.3, as the filler filled

composites increase, the melt flow was decreased which is due to the interruption of rice

husk particle in the molten polymer. Thus, increasing in filler loading; the stiffness and

brittleness of the composite increase gradually with associated decrease in the elongation

at break.

0

1

2

3

4

5

6

7

8

9

10

30 40 50

Percentage of rice husk content, (%)

Elo

ngat

ion

at b

reak

, (%

)

Fig 7. Effect of rice husk loading on the elongation at break

for recycled RHPE composite injection grade.

The limitation value of elongation at break of filled HDPE for thermoform

properties is 22 ± 2 % [6] From this study, the recycled composites have shown the

suitability to be thermoformed into packaging product as the result obtained were not

exceed the maximum value. Then, these recycled RHPE composites have the ability to be

reprocessed into the thermoform grade product.

4.0 Conclusion

The incorporation of the rice husk into HDPE matrix has resulted in the

improvement in the tensile modulus or Young’s modulus, but it caused decreases in tear

strength, tensile strength and elongation at break, which additional of rice husk contents.

This due to the greater stiffness of rice husk than that HDPE, then it brings about the

improvements in specimen Young’s modulus that determine stiffness of the specimen.

However, the immiscibility between rice husk and high-density polyethylene phases,

causing voids or weak points inside the specimens causing decreased in tear strength,

tensile strength, and elongation at break However, the best formulation that can be

thermoformed based on the optimum value of modulus and strength of the composites are

gave by the recycled RHPE composites contained 40% rice husk.

From the result obtained, there is several factors influence the suitability of this

recycled RHPE composite to be thermoformed. This can be found from the analysis of

FTIR, DSC and also MFI. The rice husk contents was not undergo degradation and

thermal degradation during the injection moulding process, as well as not formed

thermoset composite product. Besides, MFI value of recycled RHPE composite also

found fall within the range of MFI value for the standard thermoform grade that is

between 2-10 g/10 min. Moreover, it also found that, the mechanical properties of this

recycled RHPE composite were fulfilling the requirements of thermoform material grade.

This shows the suitability of recycled RHPE composite can be reprocessed or

recompounded into thermoforming grade compound/product.

5.0 References

[1] Ahmad Fuad, M.Y., Zawawi, M.T., S. Rahmat, R. Norazlan and Z. Ismail, (1997).

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[2] Antonio, F.A., and Macros, V.D. (2003). A Mechanical Analysis on Recycled

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[3] Hattotuwa, G.B.P., Ismail, H. and Baharin Azahari (2002). Tensile Properties of Rice

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[4]Herrera-Franco, P., Valadez-Gonzalez, A. And Cerventes-Uc, M., (1997).

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Engineering And Science, 10. 1131-1139.

[6] Malpas, V.E., and Kemphorn, J.T. (1986). Setting Conditions for Polyolefin

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[7]Naurah Mat Isa, (2005). Injection Moulding Process Parameters and Performance

Analysis of Column En Cap Based on RHPE Composite. Universiti


[8] Nurfatimah Abu Bakar, (2006). Effect of Oil Palm Empty Fruit Bunch Fiber Length

and Content on Mechanical Properties of PVC-U Composite. Universiti


[9]Peterson, S., Jayaraman, K. and Bhattacharyya, D., (2002). Forming Performance

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performance of recycled high density polyethylene (hdpe)/ rice husk

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