UNIVERSITI PUTRA MALAYSIA

INTAN SYAFINAZ MOHAMED AMIN TAWAKKAL

FK 2011 28

PREPARATION OF KENAF DERIVED CELLULOSE-FILLED POLYLACTIC ACID COMPOSITES

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PREPARATION OF KENAF DERIVED

CELLULOSE-FILLED POLYLACTIC ACID

COMPOSITES

INTAN SYAFINAZ MOHAMED AMIN

TAWAKKAL

MASTER OF SCIENCE

UNVERSITI PUTRA MALAYSIA

2011

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PREPARATION OF KENAF DERIVED CELLULOSE-FILLED

POLYLACTIC ACID COMPOSITES

By

INTAN SYAFINAZ MOHAMED AMIN TAWAKKAL

Thesis Submitted to the School of Graduates Studies, Universiti Putra Malaysia,

in Fulfilment of the Requirements for the Degree of Master of Science

February 2011

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DEDICATION

To my beloved mother, Rahimah Mahmud;

My loving brothers, Hafiz and Azhar;

My family members and friends.

Thanks for your encouragement, patience and loving support.

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Abstract of thesis presented to the Senate of Universiti Putra Malaysia in fulfilment

of the partial requirement for the degree of Master of Science

PREPARATION OF KENAF DERIVED CELLULOSE-FILLED

POLYLACTIC ACID COMPOSITES

By

INTAN SYAFINAZ MOHAMED AMIN TAWAKKAL

ER 2010

February 2011

Chair : Rosnita A. Talib, PhD

Faculty : Engineering

The aim of current research was to prepare kenaf derived cellulose (KDC)/polylactic

acid (PLA) composites. The KDC or α-cellulose was derived from kenaf bast fibre

(KBF) which was chemically treated via chlorination and mercerisation processes.

The characteristics of kenaf fibre and cellulose on the chemical, morphological and

physical properties were investigated by using FTIR, ESEM and density

measurements. Optimisation of the composite processing variables namely

temperature and time was carried out via RSM with respect to tensile strength and

stock temperature. The composites were compounded using internal mixer at fixed

KDC loading of 5 wt% and screw speed of 50 rpm in the temperature range of 160,

170 and 180°C for 10, 20 and 30 minutes. The effects of various KDC loadings (0-

60 wt%) on the chemical, mechanical, thermal and physical properties of the

KDC/PLA composites were also investigated.

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The cellulose was successfully derived from the KBF by removing of lignin and

hemicellulose. This was confirmed by the absence of these components from the

FTIR spectrum of the cellulose and the ESEM micrographs. From the ESEM

micrographs, the cellulose could be observed by its greater size reduction than the

raw fibre and rough surface topography. Meanwhile, the ANOVA statistical data

demonstrated that the tensile strength and stock temperature of the 5 wt% KDC/PLA

composites were affected mostly by mixing temperature with P < 0.0500. The

composites performed an optimum value at two combinations of variables which are

at 170°C for 20 minutes and 170°C for 30 minutes. Nevertheless, 170°C and 30

minutes was chosen as the best mixing conditions in order to produce composite at

higher KDC loading.

The FTIR spectrum of the KDC/PLA composite clearly indicated that no chemical

interaction was present between KDC and PLA matrix in the composite.

Interestingly, the incorporation of KDC into PLA matrix has demonstrated

remarkable improvement in the tensile strength and stiffness properties. The tensile

strength and modulus of KDC/PLA composite increased as the KDC loading

increased. The ESEM micrographs revealed evidence of good interfacial adhesion

between the KDC and PLA matrix and even distribution of the KDC in the

composite system. However, the effects of KDC loading on the flexural and notched

impact strength indicated that no remarkable changes were occurred in a range of 10

to 40 wt% of KDC loading.

The incorporation of the KDC into PLA matrix also improves the stiffness of

composite due to the enhancement of storage modulus as compared to the neat PLA.

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The DMA results demonstrated that the storage modulus of the 60 wt% KDC/PLA

composite is twice higher than the neat PLA and the rest of the composites within a

high temperature range (above 80°C). The glass transition temperatures (Tg)

generated from the loss modulus curves exhibit that the peak was shifted to higher

temperature as the percentage of cellulose loading in the composites was increased.

Thus, the addition of KDC into the PLA matrix resulted better thermal stability and

exhibited effective reinforcing agent. The water absorption of the composites

increased with increasing KDC loading while the neat PLA absorbed lesser water.

The 60 wt% KDC/PLA composite demonstrated approximately 12% of water

uptake, which is considered as relatively low percentage of water absorption in

biocomposite.

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Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia sebagai

memenuhi keperluan untuk ijazah Master Sains

PENYEDIAAN KOMPOSIT SELULOSA TERBITAN DARIPADA KENAF

TERISI POLILAKTIK ASID

Oleh

INTAN SYAFINAZ MOHAMED AMIN TAWAKKAL

Februari 2011

Pengerusi : Rosnita A. Talib, PhD

Fakulti : Kejuruteraan

Tujuan penyelidikan ini adalah untuk menghasilkan komposit selulosa terbitan kenaf

(KDC) dengan polilaktik asid (PLA). KDC atau α-selulosa telah diterbitkan daripada

gentian batang kenaf (KBF) melalui proses rawatan kimia iaitu pengklorinan dan

pengalkalian. Ciri-ciri gentian kenaf dan selulosa terhadap sifat kimia, mofologikal

dan fizikal telah dikaji dengan menggunakan teknik seperti FTIR, ESEM dan ukuran

ketumpatan. Pengoptimuman pembolehubah-pembolehubah pemprosesan komposit

terutamanya suhu dan masa telah dijalankan terhadap kekuatan regangan dan suhu

terkumpul dengan menggunakan kaedah RSM pada peratusan kandungan KDC

sebanyak 5 wt% dan kelajuan skrew sebanyak 50 rpm dengan menggunakan

pengadun pada julat suhu 160, 170 dan 180°C untuk 10, 20 dan 30 minit. Kesan-

kesan komposit bagi pelbagai peratusan kandungan KDC terhadap sifat kimia,

mekanikal, termal dan fizikal turut dikaji.

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Terbitan selulosa daripada KBF telah berjaya dihasilkan melalui penyingkiran lignin

dan hemisellulosa. Penyingkiran ini disahkan dengan ketiadaan komponen-

komponen tersebut di dalam spektrum FTIR selulosa dan mikrograf ESEM. Melalui

mikrograf ESEM, didapati selulosa memiliki garis pusat yang lebih kecil

berbandingan gentian kenaf dan topografi permukaan selulosa yang kasar telah

diperolehi. Selain itu, berdasarkan data statistik ANOVA, didapati hubungan

diantara kekuatan regangan dan suhu terkumpul terhadap pembolehubah komposit

adalah amat dipergaruhi oleh suhu pengadun dengan P < 0.0500. Komposit-

komposit ini juga menghasilkan nilai optimum pada dua kombinasi pembolehubah

iaitu pada 170°C dan 20 minit serta 170°C dan 30 minit. Bagaimanapun, 170°C dan

30 minit adalah kombinasi pembolehubah yang paling sesuai bagi menghasilkan

komposit pada peratusan kandungan KDC yang lebih tinggi.

Spektrum FTIR komposit secara jelas menunjukkan tiada interaksi kimia yang

wujud diantara KDC dan matrik PLA. Menariknya, penggabungan KDC di dalam

matrik PLA telah menunjukkan peningkatan kekuatan regangan dan ketegaran

komposit yang memberangsangkan. Kekuatan dan modulus regangan juga

meningkat dengan penambahan peratusan kandungan KDC. Mikrograf ESEM

komposit pada permukaan patah kekuatan regangan membuktikan kewujudan

lekatan yang baik diantara KDC dan matrik PLA serta taburan KDC yang sekata di

dalam sistem komposit. Walau bagaimanapun, sifat komposit terhadap kekuatan

lenturan dan impak menunjukkan tiada perubahan ketara berlaku pada peratusan

kandungan KDC dari 10 hingga 40%.

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Penggabungan KDC di dalam matrix PLA juga menambahkan ketegaran komposit.

Ini disebabkan oleh peningkatan modulus simpanan komposit apabila dibandingkan

dengan PLA tulen. Pada suhu yang tinggi (lebih 80°C), ujian DMA menunjukkan

modulus simpanan komposit pada 60% kandungan KDC adalah dua kali lebih tinggi

berbanding PLA dan komposit-komposit lain. Manakala, suhu peralihan kaca (Tg)

yang diperoleh melalui lengkungan modulus lesapan menunjukkan berlakunya

anjakan puncak ke suhu yang lebih tinggi dengan penambahan peratusan kandungan

KDC. Oleh itu, penambahan KDC ke dalam matrix PLA telah menghasilkan

kestabilan termal yang lebih baik serta membuktikan keberkesanan selulosa sebagai

agen penguat. Penyerapan air terhadap komposit didapati semakin meningkat

dengan penambahan peratusan kandungan KDC. Komposit yang mengandungi 60%

kandungan KDC menunjukkan kadar penyerapan air sebanyak 12%. Peratusan ini

bagaimanapun adalah agak rendah di dalam biokomposit.

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ACKNOWLEDGEMENTS

All praises be to the Mighty Allah S.W.T, the Merciful and the Beneficent for the

strength, patience, determination and blessing in the completion of this study. It is

impossible for me to finish this thesis all by myself without the guidance and help of

many important people.

Firstly, for the preparation of this thesis and the well going for this project, I wish to

express my acknowledgement to my main supervisor, Dr. Rosnita A. Talib who

guide me continuously and patiently reviewed this thesis. I had been receiving

invaluable guidance, encouragement and constructive criticism from my supervisor.

She has been my advisor throughout my graduate education. I would like to thank

my co-supervisor Dr. Khalina Abdan, who has been very supportive and helpful

especially during the preparation of my samples and thesis. I also appreciate her

guidance and support in supervising me. Not forgotten, my appreciation to Mr.

Khalid from International Islamic University Malaysia, (IIU) for his guidance and

help in sharing valuable experience and knowledge regarding this research.

Appreciation and thanks are also dedicated to all the staff and technicians in

Radiation Processing Technology Division, Malaysian Nuclear Agency (MNA),

Department of Food and Process Engineering UPM, Department of Chemical and

Environmental Engineering UPM and Laboratory of Biocomposite Technology,

Institute of Tropical Forestry and Forest Products (INTROP), especially to Mr.

Faizal, Mr. Bernard, Mr. Falah, Mrs. Siti Hajar, Mr. Raman, Mr. Zahir, Mr. Shah,

Mr. Ismail Abdul Ghani and Ms. Hasniza. A special thanks goes to Mr. Wan Ali,

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staff of MNA for his assistance during the preparation of samples and sharing his

outstanding knowledge. Thank you for your help and assistance throughout the

experimental work. Beside that, I would like to thank PhD students, Mrs. Behjat

Tajeddin from UPM and Mrs. Aishah @ Min Min Aung from UKM for their

encouragement and willingness in sharing experience. To INTROP’s students Ipin,

Mai, Jue and Eda thank you for your time, help and guidance.

Also last but not least, a special thanks to my family especially my beloved mother,

brothers and sister for their encouragements, patience and moral support in

completing this study. To all of my friends and colleagues especially, Faridah,

Norazlin, Nurul Lina, So’bah, Awanis, Aziana, Rohaiza, Zafirah, Che Rodiziah,

Aishah, Roazita, Intan Shidatul, Chui Yen, Hamidah and my peer group (Norma,

Siti Hajar, Faezah and Zuhair) for being supportive with their kindness and co-

operations all the way. Your supports and encouragements mean a word to me.

Thanks a lot to you all. I could not have completed this thesis without each of you.

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I certify that a Thesis Examination Committee has met on 24 February 2011 to

conduct the final examination of Intan Syafinaz Mohamed Amin Tawakkal on her

thesis entitle “Preparation of Kenaf Derived Cellulose-Filled Polylactic Acid

Composites” in accordance with the Universities and University Colleges Act 1971

and the Constitution of the Universiti Putra Malaysia [P.U.(A) 106] 15 March 1998.

The Committee recommends that the student be awarded the Master of Science.

Members of the Thesis Examination Committee were as follows:

Russly bin Abdul Rahman, PhD

Professor

Faculty of Engineering

Universiti Putra Malaysia

(Chairman)

Yus Aniza binti Yusof, PhD

Senior Lecturer

Faculty of Engineering

Universiti Putra Malaysia

(Internal Examiner)

Mohd Nordin bin Ibrahim, PhD

Associate Professor

Faculty of Engineering

Universiti Putra Malaysia

(Internal Examiner)

Rozman bin Din, PhD

Professor

School of Industrial Technology

Universiti Sains Malaysia

(External Examiner)

______________________________

ZULKARNAIN ZAINAL, PhD Professor and Deputy Dean

School of Graduate Studies

Universiti Putra Malaysia

Date:

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This thesis was submitted to the Senate of Universiti Putra Malaysia and has been

accepted as fulfilment of the requirement for the degree of Master of Science. The

members of the Supervisory Committee were as follows:

Rosnita A. Talib, PhD

Senior Lecturer

Faculty of Engineering

Universiti Putra Malaysia

(Chairman)

Khalina Abdan, PhD

Senior Lecturer

Faculty of Engineering

Universiti Putra Malaysia

(Member)

________________________________

HASANAH MOHD GHAZALI, PhD

Professor and Dean

School of Graduate Studies

Universiti Putra Malaysia

Date:

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DECLARATION

I declare that the thesis is my original work except for quotations and citations

which have been duly acknowledged. I also declare that it has not been previously,

and is not concurrently, submitted for any other degree at Universiti Putra Malaysia

or at any other institution.

_____________________________

INTAN SYAFINAZ MOHAMED

AMIN TAWAKKAL

Date: 24 February 2011

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TABLE OF CONTENTS

Page

DEDICATION ii

ABSTRACT iii

ABSTRAK vi

ACKNOWLEDGEMENTS ix

APPROVAL xi

DECLARATION xiii

LIST OF TABLES xvi

LIST OF FIGURES xvii

LIST OF ABBREVIATIONS xx

CHAPTER

1 INRODUCTION

1.1 Background 1

1.2 Research Objectives 5

1.3 Outline of the Thesis 5

2 LITERATURE REVIEW

2.1 Introduction 7

2.2 Biodegradable Polymers 8

2.3 Polylactic Acid (PLA) 9

2.4 PLA as Bio-based Packaging Materials 12

2.5 Plant Fibres and Biocomposites 15

2.6 Natural Fibres Reinforced Biopolymers 17

2.7 Kenaf (Hibiscus Cannabinus L.) 19

2.8 Lignocellulosic Fibres Structure 21

2.9 Modification of Natural Fibres 24

2.10 Mercerisation 25

2.11 The Characteristics of Short Fibres

2.11.1 Fibres/Matrix Adhesion and Interaction 27

2.11.2 Fibres Aspect Ratio 28

2.11.3 Fibres Volume Fraction 29

2.11.4 Fibres Distribution 30

2.12 Mixing Torque Curve 32

2.13 Respond Surface Method (RSM) 34

2.14 FTIR Spectroscopy 35

2.15 The Mechanical Properties 36 2.16 The Thermal Properties 41

2.17 The Physical Properties 43

3 METHODOLOGY

3.1 Introduction 46

3.2 Materials 46

3.3 The Preparation of the Cellulose from Kenaf Bast Fibre 48

3.4 The Experimental Design of the Optimisation of Processing

Variables 49

3.5 The Preparation of the Composites 51

3.6 The Preparation of the Testing Specimens 52

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3.7 Testing and Characterisation Procedures

3.7.1 FTIR Spectra Analysis 53

3.7.2 Mechanical Properties Testing 53

3.7.3 Dynamic Mechanical Analysis 54

3.7.4 Characterisation of Physical Properties 55

3.7.5 ESEM Micrograph Analysis 56

4 CHARACTERISTICS OF KENAF FIBRE AND CELLULOSE

4.1 Introduction 57

4.2 The Properties of Kenaf Fibre and Cellulose

4.2.1 FTIR Spectra 57

4.2.2 Morphology Analysis 58

4.2.3 Bulk Density 60

4.3 Discussions 61

4.4 Summary 64

5 OPTIMISATION OF THE MIXING VARIABLES

5.1 Introduction 65

5.2 The RSM of Processing Variables

5.2.1 Statistical Analysis and Response Surface on

Tensile Strength 66

5.2.2 Statistical Analysis and Response Surface on

Stock Temperature 70

5.2.3 Overlay between Responses 73

5.3 Discussions 74

5.4 Summary 79

6 EFFECTS OF THE KDC LOADING

6.1 Introduction 80

6.2 Properties of the KDC/PLA Composites

6.2.1 Fourier Transmission Infrared Spectra 80

6.2.2 Tensile Properties 82

6.2.3 Flexural Properties 84

6.2.4 Notched Izod Impact Strength 85

6.2.5 Dynamic Mechanical Analysis (DMA) 86

6.2.6 Water Absorption 90

6.2.7 Density 91

6.2.8 Morphology Analysis 91

6.3 Discussions 92

6.4 Summary 110

7 CONCLUSIONS AND RECOMMENDATIONS

7.1 Introduction 111

7.2 Summary of the Study 111

7.3 Recommendations for Future Work 113

REFERENCES 115

APPENDICES 130

BIODATA OF STUDENT 148

LIST OF PUBLICATIONS 149