CHARACTERIZATION AND BIODEGRADABILITY OF EXTRUDED

FOAMED POLYPROPYLENE FILLED PINEAPPLE LEAF FIBER

BIOCOMPOSITES

RAFIDAH BINTI RUSMAN

A project report submitted in partial fulfilment of

the requirements for the award of the degree of

Master of Science (Polymer Technology)

Faculty of Chemical Engineering

University Teknologi Malaysia

NOV 2010

iii

Specially dedicated to my beloved parents,

family and friends

Thanks for encouraging and supporting me.

iv

ACKNOWLEDGEMENT

“In the name of Allah SWT, the most gracious and most merciful”

I would like to take this opportunity to express my deepest appreciation to my

respectful supervisors, Assoc. Prof. Dr. Wan Aizan Wan Abdul Rahman and Dr.

Zurina Mohammad for their supports, supervision and guidance towards the

completion of this research.

Special thanks also go to all staffs from the Department of Polymer Engineering

supported me in my research work. I want to thank them for all their assistances,

support, interest and inspiration. Most importantly to Ms. Zainab Salleh, Mr.

Suhee Tan Hassan and Mr. Azri.

My sincere appreciation also extends to all the lecturers who have taught valuable

knowledge throughout the learning semester in UTM. Not forgetting, my course

mates and all postgraduate students for all their ideas and motivation.

Finally, I am also indebted to my beloved parents and also all the persons who

involved directly and indirectly in the success of this research. Above all, I thank

Allah the Almighty for His grace, mercy and guidance throughout my life. Thank

You.

v

ABSTRACT

Polymer foam biocomposites based on Polypropylene (PP)-Pineapple Leaf

Fiber (PALF) were successfully produced by an extrusion foaming

process. The compounding of PP with PALF was performed in twin-screw

extruder which blend the materials with dicumyl peroxide (DCP) and

chemical blowing agent (ADC). The DCP (1%) and ADC (1.5%) were

kept constant while PALF content were varied from 0% to 30% by weight.

After forming the foam, samples was prepared for water absorption test

(ASTM D-2842), density determination and biodegradability test (ASTM

G21). The PP-PALF biocomposite foam was characterized using

Thermogravimetry Analysis (TGA) and Differential Scanning Calorimetry

(DSC). It was found that PP-PALF biocomposite foam is open-cell foam

and is proved by the water absorption test which increased linearly with

increment of PALF loadings. From the DSC result, it was showed that the

percent of crystallinity decreases with increased in filler loading and the

melting temperature of the PALF-PP biocomposite foam were not much

affected by incorporation of PALF. Finally, the additions of pineapple leaf

fiber into each formulation have significantly improved the

biodegradability of the biocomposites.

vi

ABSTRAK

Biokomposit polimer berbusa berasaskan gentian daun nenas (PALF) diisi

polypropiline (PP) telah Berjaya dihasilkan melalui proses penyemperitan. Proses

penyaemperitan PP dan PALF telah dilakukan dengan menggunakan mesin

penyemperitan screw berkembar. Bahan mentah ini kemudiannya diadunkan pula

bersama-sama dicumyl perosida (DCP) dan agen pembuih kimia (ADC) untuk

menghasilkan biokomposit berbusa. Dalam kajian ini, hanya kandungan PALF

dipelbagaikan dari 0% hingga 30% daripada berat keseluruhan, manakala

kandungan DCP (1%) dan ADC (1.5%) adalah tetap. Selepas proses

penyemperitan berbusa, sampel-sampel ini kemudiannya telah menjalani proses

penentuan ketumpatan, ujian penyerapan air (ASTM D-2842) dan ujian

kebolehuraian (ASTM G21). Proses pencirian juga telah dilakukan ke atas

biokomposit berbusa tersebut. Mikrogaf optikal (SEM) pula telah digunakan

untuk mengkaji struktur sel biokomposit bebusa tersebut. Pemerhatian

menggunakan SEM telah mendedahkan bahawa struktur sel biokomposit berbusa

ini terdiri daripada sel-sel terbuka. Dari proses penentuan ketumpatan pula telah

menunjukan berlakunya peningkatan ketumpatan bagi setiap komposit berbusa

apabila kandungan PALF ditambah. Peningkatan kandungan PALF juga

mengurangkan peratusan hablur yang hadir dalam setiap biokomposit berbusa

tersebut. Akhir sekali, penambahan PALF juga telah meningkatkan kadar

kebolehuraian bagi setiap biokomposit berbusa tersebut.

vii

TABLE OF CONTENTS

CHAPTER

TITLE PAGES

DECLARATION ii

DEDICATION iii

ACKNOWLEDGEMENT iv

ABSTRACT v

ABSTRAK vi

TABLE OF CONTENT vii

LIST OF TABLES x

LIST OF FIGURES xi

LIST OF ABBREVIATIONS xiv

LIST OF APPENDICES xv

1

INTRODUCTION

1.1 Research Background 1

1.2 Problem Statement 4

1.3 Objectives of Study 5

1.4 Scope of Research 5

1.5 Significance of Study 6

2

LITERATURE REVIEW

2.1 Introduction 8

2.2 Polymer Biocomposite 9

2.3 Natural Fiber 12

2.3.1 Pineapple Leaf Fiber (PALF) 14

2.4 Polymeric Foams 15

2.4.1 The Formation of Foam Structure in Polymer 26

2.4.2 Foam Morphology 30

2.4.3 Characteristic of Foaming Agent 31

2.5 Biodegradation of Polypropylene 34

viii

3

RESEARCH METHODOLOGY

3.1 Introduction 39

3.2 Raw Material Preparation

3.2.1 Polypropylene (PP) 39

3.2.2 Preparation of PALF 40

3.2.3 The Foaming Agent 42

3.2.4 Foam Nucleating Agent 42

3.3 Extrusion Foaming 43

3.4 Testing Method 45

3.4.1 Density Determination 46

3.4.2 Scanning Electron Microscope 46

3.4.3 Water Absorption of Rigid Cellular Plastics 48

3.4.4 Determining Resistance of Synthetic Polymeric

Materials to Fungi 51

3.4.5 Differential Scanning Calorimetry 52

3.4.6 Thermogravimetry Analysis 53

4

RESULTS AND DISCUSSION

4.1 Physical Properties 55

4.1.1 Density 55

4.1.2 Morphological Analysis 57

4.2 Thermal Properties

4.2.1 Differential Scanning Calorimetry 59

4.2.2 Thermogravimetry Analysis 61

4.3 Physical Tests

4.3.1 Water Absorption 63

4.3.2 Biodegradability 65

ix

5

CONCLIUSIONS AND RECOMMENDATIONS

5.1 Conclusion 68

5.2 Recommendation 70

REFERENCES 71

APPENDICES 78

x

LIST OF TABLES

TABLE

NO. TITTLE PAGE

2.1 Advantage and Disadvantage of Composite 10

2.2 Physical and Mechanical Properties of PALF 15

2.3 Foam Properties and Application Attributes 17

2.4 Various Literature Reports on Biodegradation Polypropylene 38

3.1 Properties of Polypropylene (TITANPRO6331) 40

Typical Physical Properties of Cellcom AC-1000C Chemical

3.2 Raw Materials Formulation and Composition 44

3.3 Reagents for Nutrients Salts Agar 52

4.1

Density of pure PP foam and PP/PALF foam composites for

various PALF content 55

4.2 The thermal parameter DSC of PP/PALF foam composite 59

4.3 TGA data for pure PP and PP/PALF foam biocomposites 62

4.4

Percentage of Water Absorption of pure PP foam and

PP/PALF foam composite

63

xi

LIST OF FIGURES

FIGURE

NO. TITTLE PAGE

2.1 Categories of Natural Fiber 14

2.2 Effect of Silane Treated Rossells and the Addition of

Compatibilizer on Tensile and Impact Strength

18

2.3 Relationship between compressive strength and density of PP

foam.

20

2.4 Effects of blowing time and cross-linking agent (VTMOS) on

the density of PP foam at 0.5 phr ADCA. (BPO: 0.5 phr;

CAT: 0.15 phr).

21

2.5 Effects of blowing time and cross-linking agent (VTMOS) on

the density of PP foam at 1.0 phr ADCA. (BPO: 0.5 phr;

CAT 0.15 phr).

21

2.6 Effect of cross-linking agent (VTMOS) on the expansion

ratio of PP foam. (BPO: 0.5 phr; CAT: 0.3 phr, blowing time:

30 min).

22

2.7 Effect of cross-linking agent (VTMOS) on the gel fraction of

PP foam. (BPO: 0.5 phr.)

23

2.8 Effect of cross-linking accelerator (CAT) on the gel fraction

of PP foam. (BPO: 0.5 phr)

24

2.9 Effect of cross-linking initiator (BPO) on the gel fraction of

PP foam. (VTMOS: 2 phr; CAT: 0.3 phr).

25

2.10 Surface morphology of composites: (a) unmodified,

(b) OTMS_3hr,

xii

(c) MAPP_1phr, (d) MAPP_2phr, (e) MAPP_4phr, (f)

MAPP_6phr, (g) MAPP_8phr and (h) MAPP_10phr.

26

2.11 The Principle of Batch Foaming 27

2.12 The Principle of Continous Foaming 28

2.13 Morphological Changes in the Extrudate During

Microcellular Processing

29

2.14 Comparative lengths for morphological features in a foam 31

2.15 Typical isothermal gas evolution curves for

azodicarbonamide at various temperatures.

33

2.16 Overview of degradation of polymers (Adapted from Vasile) 35

3.1 Two Roll Mill Machine Used For Remove Water 41

3.2 Long PALF Extracted From Raw Leaf 41

3.3 Chopped PALF 41

3.4 Schematic of an extrusion foaming process 45

3.5 Sample placed on the stub before coated 47

3.6 Sample placed on the stub after coated with platinum 48

3.7 Empty submerged jig 49

3.8 Submerged jig with test specimens

50

4.1 Density determination of foam samples at different filler

loading

56

4.2 Effect of PALF content on cell morphology at (a) 0 wt%, (b)

10 wt%, (c) 20 wt%, and (d) 30 wt%

58

xiii

4.3 TGA curves of PP/PALF foam for various PALF contents 61

4.4 Percentage of water absorption of pure PP foam and

PP/PALF foam composite with different filler loading

64

4.5 Photograph of microbial growth on the film surface of PP/PALF 66

foam composites at (a) 0 wt%, (b) 10 wt%, (c) 20 wt%, and

(d) 30 wt%

xiv

LIST OF ABBREVIATIONS

PP

Polypropylene

PALF

Pineapple Leaf Fiber

DCP

Dicumyl Peroxide

ADC

Azodicabonamide

ASTM

American Society for Testing and Materials

TGA

Thermogravimetry Analysis

DSC

Diffential Scanning Calorimetry

SEM

Scanning Electron Microscope

SHSD

Sunflower Hull Sanding Dust

SITRA

South India Textile Research Association

MAPP

Maleic Anhydride Polypropylene

OTMS

Octadecyltrimethoxysilane

ADCA

Azodicarbonate

BPO

Benzyl Peroxide

CAT

di-nbutyltin dilaurate

VTOMS

Vinyl Trimethoxy Silane

CFA

Chemical Blowing Agent

PFA

Physical Blowing Agent

VOC

Volatile Organic Content

HC

Hydrocarbon

CFC

Chlorofluorocarbon

HFC

hydrofluorocarbon

HDPE

High Density Polethylene

LLDPE

Low Linear Density Polyethylene

LDPE

Low Density Polyethylene

EM

Effective Microorganism

∆Hf

Heat of Fusion

Tm

Melting Temperature

Xcom

Percent Crystallinity

Xpp

Crystallinity of PP in the Composite

∆H

Heat of Fusion of Perfectly Crystalline

xv

LIST OF APPENDICES

APPENDIX TITLE PAGE

A Cell Morphology of Pure PP Foam 78

B Cell Morphology of PP/PALF (10% PALF) Biocomposite

Foam 78

C Cell Morphology of PP/PALF (20% PALF) Biocomposite

Foam 79

D Cell Morphology of PP/PALF (30% PALF) Biocomposite

Foam 79

E Raw Data for Water Absorption Determination 80

F TGA Thermogram for PP/PALF (10% PALF) 81

G TGA Thermogram for PP/PALF (20% PALF) 82

H TGA Thermogram for PP/PALF (30% PALF) 83

I DSC Thermogram for PP/PALF (10% PALF) 84

J DSC Thermogram for PP/PALF (20% PALF) 84

K DSC Thermogram for PP/PALF (30% PALF) 85

CHAPTER 1

INTRODUCTION

1.1 Research Background

The use of polymeric foam in today‟s world has constantly increased. Many

reasons support this growth: light weight, insulation properties, softness, excellent

strength/weight ratio, material costs and energy absorption performance. Many times

reductions after foaming in material costs are around 30% without compromising the

function or required strength, which is one of the advantages that could lead to even

wider use of foams in industry. The chemicals used are today environmental friendly

and the mechanical and barrier properties can be greatly affected by multilayer

constructions; mechanically strong sandwich structures can be produced with solid skin

layers, low gas permeability polymers and tie layers support their use for high barrier

packages (Krayink et al., 1987).

The main applications for foamed plastics can be found in the building,

automobile, packaging and sport industries. They include the end products for insulative

2

sheets, floor coverings, and profile for finishing, automobile linings, packaging films,

cable wires, interior finishing, shoes and cups (Kumar, 1993).

Because of environmental demands, foamed polymers have also been threatened

and raw material and process manufactures have been forced to find solutions for

recyclable polymers and alternatives for blowing agents‟ deleterious effects on the ozone

layer. These challenges have led studies more away from the traditional materials,

polystyrene and polyurethane and towards the use of polyolefins, polyethylene and

polypropylene (Fox and Goodman, 1993). The tremendous growth in the use of foams in

the last three decades has also created a serious problem of waste disposal and to

overcome this problem, natural fiber will be added to make the foam biodegradable

(Daniel Klempner and Vahid Sendijarevic, 2004).

In Malaysia, agriculture is an important sector of economy. Traditionally,

agricultural materials have been shipped away for processing, or disposed of

postharvest. Diversification of the industry is crucial in encouraging economic stability

and growth. Value-added processing would helps in agricultural diversification.

Pineapple Leaf Fiber (PALF), the subject of the present study, is a waste product of

pineapple cultivation. Hence, pineapple fiber can be obtained for industrial purposes

without any additional cost.

Traditional plastic materials are reinforced by the non-biodegradable fiber, which

are both expensive and harmful to the environment. A fiber based biocomposite material

contains polymers reinforced with natural fiber. There are number of advantages of

using natural fibers in biocomposites, among which are: a) natural fiber will make the

material partially biodegradable; b) natural fiber, in this research is PALF is currently

disposed of by burning; and c) PALF is a low cost, low density and low energy

consumption. Over the past decade, cellulosic fillers have been of greater interest as they

3

improve composites mechanical properties compared to those containing non-fibrous

fillers. In recent years, thermoplastic materials have been increasingly used for various

applications (Folkes, 1982).

Research on a cost effectiveness modification of natural fiber is necessary since

the main attraction for today‟s markets of biocomposites is the competitive cost of

natural fiber. This research attempts to address the following question: do PALF have

any influence on the foam properties. Polymer reinforced biocomposites have

demonstrated a marked improvement in the physical properties of polymeric materials.

Natural fibers have proven to yield many desirable properties when utilized as

reinforcing agents in polymer composite (Sui et al., 2009).

Since the tensile strength for these natural fibers are low, the composites reach

only of about 60 % of the tensile strength of the GF-PP composites. However the

Young‟s moduli are commonly higher than those of GF-PP composites. By considering

the economy factors where the natural fiber are abundant and are relatively cheap

compare to engineering glass fiber, natural fibers have their significant important in the

composite field as reinforcement.

Although there are not many tests carried out for the flexural properties of

composites, this property is important to study the fracture behavior. Regarding PALF

reinforced polyester, Uma Devi et al. (1997) pointed that the addition of fiber made the

composite more ductile. In her work, the flexural strength values of the PALF-polyester

composites were less than the pure polyester at low weight fractions (10 wt %) of the

fiber. Further increased of the fiber loading, the flexural strength had improved by

nearly 120 % for composite containing 30mm long fibers. But when reach more than 30

wt %, the flexural modulus decreased. At 40 wt %, the flexural strength decreased cited

13 % of value. To explain this, the author pointed that higher fiber loading encouraged

4

fiber-to-fiber interaction and the fiber were not well dispersed within the resin latex. For

this research, the best result was obtained at fiber loading of 30 wt %.

In order to take full advantage of the natural agriculture processing by-product,

this study will comminute and compound PALF in Polypropylene (PP) matrix, which

will then be foamed to enhance light weight properties of the finished polymer foam

biocomposites. Generally, this research is conducted to develop PP/PALF foam

biocomposites to attain the desired properties for the application in construction

(pellets), packaging (example: egg tray, fruits tray) and furniture industry (synthetic

wood).

1.2 Problem Statement

The use of plastic foam creates lots of difficulties and problem such as high cost

and environmental pollution. Moreover polymer foams difficult to dispose. Thus, the

best solution to overcome these problems is to produce partially biodegradable materials

such as polymer foam biocomposite. Creating a cellular structure to produce foam

thermoplastics and utilizing inexpensive fillers to manufacture thermoplastic composites

are two effective ways of addressing the price challenge and improve biodegradability.

The large consumption of thermoplastics continues to draw deep development

effort to improve resin manufacturing, which becomes phenomenal support to the foam

industry. It is well-known that thermoplastic foams have lot advantages compared to

thermoplastic itself. However, the research and development in thermoplastic foam

5

biocomposite is less conducted. Thus, this study emphasis on the extrusion foaming

process for PP/PALF foam biocomposite. This project is mainly to evaluate:

i. Is PALF enhance the physical, thermal and morphological properties and

reduce weight of the biocomposite?

ii. What is the effect of PALF loading on the biocomposite foam?

iii. Does addition of PALF improved the biodegradability of the

biocomposites?

1.3 Objectives of Study

The objectives of this research are to:

i. To study the cell morphology and cell size of the composite by Scanning

Electron Microscopy (SEM).

ii. To investigate the effect of filler loading on physical and thermal

properties of PP/PALF foam biocomposites.

iii. To investigate the effect of filler loading on the biodegradability.

1.4 Scopes of Research

The scopes of research are:

i. Preparation of short pineapple leaf fiber (PALF)

6

ii. Extrusion Foaming

iii. Testing to study properties:

- Density

- Water Absorption of Rigid Cellular Plastics (ASTM D2842)

- Resistance of Synthetic Polymer Material to Fungi

(ASTM G21)

v. Scanning Electron Microscope (SEM) to study the cell morphology and

cell size

iv. Differential Scanning Calorimetry (DSC)

v. Thermogravimetry Analysis (TGA)

This study focuses on the effect of foaming process condition and the properties

of PP/PALF foam biocomposite. Foam biocomposites are prepared by using extrusion

foaming technique. Materials used are Polypropylene (PP), pineapple leaf fiber (PALF),

azodicarbonamide (ADC) and dicumyl peroxide (DCP). The filler loading varies in

order to study the effects on foam properties. The foam biocomposite cell structures are

characterized by using Scanning Electron Microscope (SEM).

1.5 Significance of Study

Biocomposite based on polypropylene (PP) and natural filler (pineapple leave

fiber) use as synthetic wood that can replace the wood in the furniture industries and

packaging such as egg and fruit tray in Malaysia. Due the abundance of natural filler

(rice husk, rice straw, kenaf, etc.) in Malaysia, biocomposite simply provides the

alternative for wood apart from several other benefits such as biodegradability, low

density, renewable resources, non-abrasive and low cost due to low material usage. In

7

addition, foaming is introduced to enhance the light weight of material to suit certain

industrial needs. The establishment of structure and properties relationship will help

manufacturer to predetermine the biocomposite material properties based on the

component composition and processing parameter since this relates to the structural and

morphological behavior. In brief, this study is important for development of

thermoplastics filled foam biocomposite as it will provide lots of advantages in the

related industries.

72

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