universiti putra malaysia development of …psasir.upm.edu.my/5426/1/fk_2008_46.pdf · sintesis...

UNIVERSITI PUTRA MALAYSIA

DEVELOPMENT OF POLYURETHANE/CLAY NANOCOMPOSITES BASED ON PALM OIL POLYOL

TEUKU RIHAYAT

FS 2008 46

DEVELOPMENT OF POLYURETHANE/CLAY

NANOCOMPOSITES BASED ON PALM OIL POLYOL

TEUKU RIHAYAT

DOCTOR OF PHILOSOPHY

UNIVERSITI PUTRA MALAYSIA

2008

DEVELOPMENT OF POLYURETHANE/CLAY NANOCOMPOSITES BASED ON

PALM OIL POLYOL

TEUKU RIHAYAT

Thesis Submitted to the School of Graduate Studies, Universiti Putra Malaysia, In

Fulfilment of the Requirements for the Degree of Doctor Of Philosophy

November 2007

ii

DEDICATION

Thanks to my beloved wife, sons, parents and my loving family for their patience and

support during the long preparations of this thesis

iii

Abstract of thesis presented to the Senate of Universiti Putra Malaysia

In fulfilment of the requirements for the degree of Doctor of Philosophy

DEVELOPMENT OF POLYURETHANE/CLAY NANOCOMPOSITES BASED

ON PALM OIL POLYOL

By

Teuku Rihayat

November 2007

Chairman : Assoc.Prof. Dr. Saari B. Mustapha

Faculty : Engineering

Polyurethanes (PURs) are very versatile polymeric materials with a wide range of

physical and chemical properties. PURs have desirable properties such as high abrasion

resistance, tear strength, shock absorption, flexibility and elasticity. Although they have

relatively poor thermal stability, this can be improved by using treated clay.

Polyurethane/clay nanocomposites have been synthesized from renewable sources. A

polyol for the production of polyurethane by reaction with an isocyanate was obtained

by the synthesis of palm oil-based oleic acid with glycerol. Dodecylbenzene sulfonic

acid (DBSA) was used as catalyst and emulsifier. The unmodified clay (kunipia-F) was

treated with cetyltrimethyl ammonium bromide (CTAB-mont) and octadodecylamine

(ODA-mont). The d-spacing in CTAB-mont and ODA-mont were 1.571 nm and 1.798

nm respectively and larger than that of the pure-mont (1.142 nm). The organoclay was

completely intercalated in the polyurethane, as confirmed by a wide angle x-ray

diffraction (WAXD) pattern.

iv

Polyurethane/clay nanocomposites were prepared by a pre-polymer method and were

evaluated by fourier transform infrared (FTIR) spectra to determine micro-domain

structures of segmented PU, CTAB-mont-PU 1, 3, 5 wt% and ODA-mont-PU 1, 3, 5

wt%. The morphology of the nanocomposites was characterized by X-ray diffraction (X-

RD) and the pattern showed that all of the nanocomposites produced from this work are

of the intercalated type. These were further confirmed by transmission electron

microscopy (TEM) observation and scanning electron microscopy (SEM) when the

surfaces of the materials were studied. Thermal stability was investigated with

thermogravimetric analysis (TGA). The results showed that adding clay demonstrated

better thermal stability in comparison with the virgin polyurethane. Onset degradation of

pure PU is at 200oC, and is lower than that of the CTAB-mont PU and ODA-mont PU

which takes place at about 318oC and 330

oC, respectively. The mechanical properties

(including the dynamic mechanical properties) of pure polyurethane (PU) and PU/clay

nanocomposites, were measured. The modified organoclay had a remarkably beneficial

effect on the strength and elongation at break of the nanocomposites, which both

increased with increasing clay content with the increase of the tensile strength of more

than 214% and 267% by the addition of only 5 wt% of the montmorillonite CTAB-mont

PU and ODA-mont PU, respectively.

v

Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia

Sebagai memenuhi keperluan untuk ijazah Doktor Falsafah

Pembangunan Poliuretana/tanah liat Bernano Komposit Berasaskan

Poliol Minyak Sawit

Oleh

Teuku Rihayat

Nopember 2007

Pengerusi : Prof. Madya Dr. Saari B. Mustapha

Faculti : Kejuruteraan

Poliuretana (PUR) merupakan bahan polimer yang sangat versatil yang mempunyai ciri-

ciri fizikal dan kimia yang sangat luas. PUR juga mempunyai sifat-sifat yang menarik

seperti ketahanan lelasan, kekuatan koyak, penyerapan kejutan, fleksibiliti dan

kekenjalan yang tinggi. Walaupun PUR mempunyai kestabilan terma yang rendah tetapi

ia masih boleh diperbaiki dengan mengunakan tanah liat terawat. Polyurethane/tanah liat

bernano komposit telah disintesa daripada bahan boleh diperbaharui. Bahan poliol bagi

penghasilan polyurethane melalui tindakbalas dengan isosianat telah diperolehi melalui

sintesis asid oleic dari minyak sawit dengan gliserol. Asid dodecylbenzene sulfonic

(DBSA) pula berfungsi sebagai pemangkin dan pengemulsi. Tanah liat asal (Kunipia-F)

telah dirawat dengan cetyltrimethyl bromide ammonium (CTAB-mont) dan

octadodecylamine (ODA-mont). Jarak d pada CTAB-mont dan ODA-mont adalah 1.571

nm dan1.798 nm yaitu lebih besar daripada mont tulen (1.142 nm). Tanah liat telah

tersisip ke dalam PU sebagai ditunjukkan pada corak WAXD.

vi

PU/tanah liat bernano komposit telah disediakan daripada kaedah prapolimer dan dinilai

melalui fourier transform infra red (FTIR) rajah bagi menentukan struktur mikro domain

bersegmen PU, CTAB-mont PU 1, 3, 5 wt% dan ODA-mont-PU 1, 3, 5 wt%. Morfologi

ke atas nanokomposit telah digambarkan sifatnya melalui belauan X-ray (X-RD) dan

corak tersebut menunjukkan bahawa kesemua nanokomposit yang terhasil dalam kajian

adalah dari jenis ”intercalated”. Kajian lebih lanjut dilakukan dengan menggunakan

kaedah “transmission electron microscopy” (TEM) dan “scanning electron microscopy”

(SEM) untuk mempelajari permukaan dari bahan material tersebut. Kestabilan terma

bahan dikaji melalui analisis termogravimetri (TGA). Kajian menunjukkan penambahan

tanah liat menghasilkan kestabilan terma yang lebih baik berbanding PU tulen. Sifat-

sifat mekanikal (termasuk sifat-sifat mekanikal dinamik) bagi PU tulen dan PU/tanah liat

bernano komposit telah diukur. Kajian mendapati tanah liat berorgano memberikan

peningkatan yang memberangsangkan dalam sifat tegang dan suhu peralihan kaca,

dimana kedua sifat tersebut meningkat dengan penambahan tanah liat berorgano,

dimana kenaikan terhadap kekuatan tegangan sebanyak 214% dan 267% dengan

penambahan hanya 5 wt% CTAB-mont PU dan ODA-mont PU.

vii

ACKNOWLEDGEMENTS

First and foremost, I would like to extend my deepest praise to Allah S.W.T who has

given me the patience, strength, determination and courage to the complete this thesis.

I would like to express my appreciation to all of the individuals who contributed to this

project, in particular, the chairman of my supervisory committee, Associate Professor

Dr. Saari B. Mustapha, for his guidance, constructive comments, continuous support,

and advice throughout the duration of this study. I extent my sincerely thank to my

members of the supervisory committee, Professor Dr. Wan Md Zin B. Wan Yunus, Dr.

Suraya Abdul Rashid and Dr. Khairul Zaman B. Hj. Mohd. Dahlan for their supervision,

support and suggestions. I also wish to express my appreciation to Mr. Mohd Hilmi

B.Mahmood, this work could have not been complete without the aid of him.

Profound gratitude is also extended to Universiti Putra Malaysia (UPM), and Malaysian

Nuclear Agency (Nuclear Malaysia) in providing the needed facilities and equipment.

Sincere thanks are also extended due Mr. Mohd. Zahid, Mr. Rosley Che Ismail,

Kamarolzaman Hussein and Ms. Rida Anak Tajau for their assistance and constructive

advice during the experimental work

Last but not least, my deepest affection and gratitude goes to my dearest, sons, parents,

my loving family and friends for their constant support and care that made things

possible.

viii

I certify that an Examination Committee has met on 15 November 2007 to conduct

the final examination of Teuku Rihayat on his Doctor Of Philosophy thesis entitled

“Development of Polyurethane/ Clay Nanocomposites Based on Palm Oil Polyol” In

accordance with Universiti Pertanian Malaysia (Higher Degree) Act 1980 and

Universiti Pertanian Malaysia (Higher Degree) Regulation 1981. The Committee

recommends that the candidate be awarded the relevant degree.

Members of the Examination Committee are as follows:

Robiah Yunus, PhD

Associate Professor

Faculty of Engineering

Universiti Putra Malaysia

(Chairman)

Fakhru’l-Razi Ahmadun, PhD

Professor



(Internal Examiner)

Luqman Chuah Abdullah, PhD

Associate Professor



(Internal Examiner)

Zainal Ariffin Mohd. Ishak, PhD

Professor

School of Material & Mineral Resource Engineering

Universiti Sains Malaysia

(External Examiner)

HASANAH MOHD. GHAZALI, PhD

Professor/Deputy Dean

School of Graduate Studies

University Putra Malaysia.

Date : 29 January 2008

ix

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

accepted as fulfilment of requirement for the degree of Doctor of Philosophy. The

members of the Supervisory Committee are as follows:

Saari Mustapha, PhD

Associate Professor


University Putra Malaysia

(Chairman)

Wan Md. Zin B. Wan Yunus, PhD

Professor

Fakulty of Science


(Member)

Suraya Abd. Rashid, PhD

Lecturer



(Member)

Khairul Zaman B. Hj Mohd. Dahlan , PhD

Malaysian Nuclear Agency

(Member)

AINI IDERIS, PhD

Professor and Dean

School Of Graduate Studies


Date : 21 February 2008

x

DECLARATION

I hereby declare that the thesis is based on my original work except for quotations

and citations which have been duly acknowledged. I also declare that it has not been

previously or concurrently submitted for any other degree at Universiti Putra

Malaysia or other institutions.

TEUKU RIHAYAT

Date : 27 January 2008

xv

LIST OF FIGURES

Figure Page

1.1 Structure of 2:1 phyllosilicates

(modified from Alexandre, M. and Dubois, P., 2000) 8

2.1. First synthesized aliphatic isocyanates by Wurtz 14

2.2. DuPont’s Carothers reaction to form nylon 66

(modified from Markush, P.H., and Schmelzer, H.G., 1997) 14

2.3. Father of Polyurethane chemistry

(Modified from Edwards, K.N., 1981) 15

2.4. (a) Schematic representation of the structure of segmented

polyurethanes and (b) two-phase structure of the bulk polymer

(Modified from Petrovic, Z.S and Ferguson, J., 1991) 19

2.5. Chemical structures of the major commercial diisocyanates 20

2.6. Resonance possibilities in the isocyanate group 22

2.7. Reaction of active hydrogen containing compound

on the isocyanate group 22

2.8. Reaction of isocyanate with alcohol 23

2.9. Reaction of reversal urethane to be isocyanate and alcohol 23

2.10. Reaction of isocyanate with water to be urethane foam 24

2.11. Produce a substituted urea 24

2.12. Reaction of carboxylic acids react with isocyanates through the

hydroxyl group 25

2.13. Reaction of isocyanates reacts with amines to produce

disubstituted ureas 25

2.14. Reaction between the urea (from amine plus isocyanate) and the

isocyanate forms a biuret 26

xvi

2.15. Reaction between the urethane (from alcohol plus isocyanate) and

the isocyanate forms an allophanate 26

2.16. General structure of polyether (modified from Oertel, G., 1985) 29

2.17. Structure of polyester (modified from Oertel, G., 1985) 30

2.18. Reaction of castor oil (modified from M.Hilmi, 1987) 33

2.19. Water chain extender (modified from Hilmi Mahmood, M., 1987) 35

2.20. TDI and MDI prepolymer reaction 41

2.21 1.4-butanediol 42

2.22. (a) world polyurethane consumption

(b) Southeast Asia polyurethane 45

2.23. Alkyl chain aggregation in 2/1 clay mineral:

(a) monolayer, (b) bilayer, (c) pseudotrimolecular

layer of chain lying flat on the surface, and

paraffin-type monolayer (modified from Lagaly, G., 1986) 52

2.24 Alkyl chain aggregation models: (a) short chain lengths,

the molecules are effectively isolated from each other,

(b) medium lengths, quasidiscrete layers form with

various degree of in plane disorder and interdigitation

between the layers and (c) long lengths, interlayer order

increases leading to a liquid-crystalline polymer

environment. Open circles represent the CH2

segments while cationic head groups are

represented by filled circles. (modified from Vaia,

R.A., et al., 1999). 53

2.25. Scheme of possible polymer-layered silicate structures:

(a) phase separated microcomposites; (b) intercalated

nanocomposite and (c) exfoliated nanocomposite.

(modified from Alexandre, M. and Dubois, P., 2001) 54

2.26. XRD patterns of the SWy-2 (left) and the CWC

(right) clays before (bottom) and after (top)

alkylammonium treatment. The spectra are

displaced vertically for clarity. (modified from

Kornmann, X., et al., 2001) 55

xvii

2.27. Bragg’s law dependencies for Cu-Kα1 radiation with

λ = 0.1540562 nm. The straight line is given by Equation 2.19;

correlation coefficient R = 1.0000.

(modified by Utracki, L.A, 2004) 57

2.28 Temperature dependence of storage modulus (G’),

loss modulus (G”), and their ratio (tan δ) for

PLACNs and the corresponding matrices:

(a) with out o-PCL and (b) with o-PCL. (modified

from Ray, S.S. et al., 2002) 61

2.29 Temperature dependence of storage G’, loss G”

moduli and tan δ for the PP-MA and PPCNs

(modified from Nam, P.H., et al., 2001) 63

2.30 Schematic illustration of formation of hydrogen

bonds in N6/MMT nanocomposites (modified from Ray, S.S.

and Okamoto, M., 2003) 64

2.31 View of the applied deformation (tensile tests) as compared

with the preferential orientation of the montmorillonite sheets.

(modified from Varlot, K.M., 2001) 66

2.32 Effects of C16–MMT loading on the mechanical

tensile properties of the hybrids. (modified from

Chang, J.H. and Park, D.K., 2001) 69

2.33. TGA curves of PE and PE/clay nanocomposites in

nitrogen atmosphere (modified from Zhao, C. et al., 2005) 71

2.34. TGA thermograms of epoxy with (a) OC series and

(b) UC series (modified from Mohan, T.P. et al. 2006) 73

2.35. TGA thermographs of TGDDM and modified TGDDM.

(modified from Hussain, M. and Simon, G.P. 2003) 74

2.36. TGA thermograms of clay, organoclay, and PBT hybrids.

(modified from Chang, J.H., et al. 2003) 75

3.1. Synthesis of polyurethane 82

3.2. Synthesis of organophilic clays 83

3.3. Thermo Haake Polydrive machine 84

3.4. HSINCHU hot and cold press machine 85

xviii

3.5. (a) montmorillonite modified (b) PU/clay nanocomposites

based on palm oil 85

3.6. Gel Permeation Chromatography (HLC-8020 TOSOH, Japan)

Machine 87

3.7. Fourier Transform Infrared Spectra (FTIR Spectrum 2000,

Perkin Elmer, USA) Machine 88

3.8. Dynamic mechanical analysis machine 90

3.9. Instron 4468 machine 90

3.10 Representative samples for PU/clay nanocomposite before

tensile test 91

3.11 Representative samples for PU/clay nanocomposite

after tensile test 91

3.12 Mitutoyo thickness gage 92

3.13 A Perkin Elmer instrument thermogravimetric analyses (TGA) 94

4.1. The FTIR spectra of the synthesized polyol based on palm oil 102

4.2. The FTIR spectra of the synthesis polyurethane based on

palm oil polyol 102

4.3 The GPC profiles of the polyol based on palm oil 105

4.4. The GPC profiles of the synthesis polyurethane based on

palm oil polyol 106

4.5. The WAXD pattern of pure-PU 109

4.6. Dispersive behavior of montmorillonite 110

4.7. The WAXD pattern of CTAB-mont-PU 111

4.8. The WAXD pattern of ODA-mont-PU 111

4.9. The FTIR spectra of pure PU and 1,3,5% CTAB-mont-PU 113

4.10. The FTIR spectra of pure PU and 1,3,5% ODA-mont-PU 114

xix

4.11. Tensile strength of pure PU and PU/clay nanocomposites 118

4.12. Elongation at break of pure PU and PU/clay nanocomposites 119

4.13. Experimentally measured modulus and theoretical predictions

by two different models : Guth and Halpin-Tsai equations

for (a) CTAB-mont-PU and (b) ODA-mont-PU. 121

4.14. DMA curves for tan δ of pure PU and PU/clay nanocomposites

CTAB-mont- PU 124

4.15. DMA curves for tan δ of pure PU and PU/clay nanocomposites

ODA-mont- PU 124

4.16. The TGA curves of pure PU and PU/clay nanocomposites

CTAB-mont- PU 126

4.17. The TGA curves of pure PU and PU/clay nanocomposites

CTAB-mont- PU 126

4.18. First order kinetic plot for pure polyurethane 129

4.19. First order kinetic plot for PU/Clay nanocomposites

CTAB 1 wt% 129


CTAB 3 wt% 130


CTAB 5 wt% 130


ODA 1 wt% 131


ODA 3 wt% 131


ODA 5 wt% 132

4.25. SEM micrographs of interfacial adhesion between nanoclay

and matrix PU 133

4.26. SEM micrographs of a good dispersion between nanoclay

and ODA-Mont- PU 3 wt% 133

xx


CTAB 1 wt% 136


ODA 1 wt% 136


CTAB 3 wt% 137


ODA 3 wt% 137


CTAB 5 wt% 138


ODA 5 wt% 138

xxi

LIST OF SYMBOLS AND ABBREVIATIONS

Å Amstrong

API Alliance for the polyurethanes industry

ASTM American Society for Testing and Materials

C18 Octadecylammonium

C18-MMT Octadecyl ammonium montmorillonite

CEC Cation exchange capacity

CTA-MMT Cetyltrimethyl ammonium montmorillonite

DDA-MMT Dodecyl ammonium montmorillonite

DMA Dynamic mechanical analysis

Eb Elongation at break

EVA Poly(ethylene-co-vynil acetate)

EVOH Ethylene vynil alcohol

FTIR Fourier transforms infrared spectroscopy

GPC Gel permeation chromatography

HSC Hard segment concentration

HCl Hydrochloric acid

HDPE High molecular weight

HRR High release rate

MMW Medium molecular weight

MW Molecular weight

MMT Montmorillonite

MPa Mega Pascal

xxii

MWD Molecular weight distribution

Na-MMT Sodium montmorillonite

NCH Nylon clay hybrid

NR Natural rubber

PCL Poly(ε-caprolactone)

phr Part per hundred

PLA Poly (L-lactide)

PLS Polymer layered silicate

PS Polystyrene

PPMA Poly (n-propyl methacrylate)

PP-MA Maleic anhydride modified polypropylene

PUEs Polyurethane Elastomers

PUR Polyurethane

PVA Poly(vynil alcohol)

PVC Poly vynil chloride

PVCH Poly(vynilpyridine)

SSC Soft segment concentration

Tg Glass transition temperature

TGA Thermogravimetric analysis

TS Tensile strength

TGDDM Terafunctional epoxy resin tetraglycidyl diaminodiphenylmethane

Wt% Weight percent

WAXD Wide angle x-ray diffraction

xxiii

XRD X-ray diffraction

µm Micrometer

12-mont 12-aminolauric acid modified montmorillonite

xiv

LIST OF TABLES

Table Page

2.1. Production volume of castor oil by major producers (x1000 t) 33

2.2. Chemical formula and characteristic parameter of commonly

used 2:1 phyllosilicates 51

2.3 Tensile Properties of Organoclay/BTDA-ODA

Nanocomposites at Different Compositions. (modified from 67

Tyan, H.L., 2000)

2.4. Tensile Properties of PETN/C16-MMT

(modified from Chang, J.H. and Park, D.K., 2001) 69

2.5 General properties of PBT nanocomposite fiber

by in-situ interlayer polymerization

(modified from Chang, J.H., et al. 2003) 75

4.1. Summary of the d-spacing (nm) and 2θ (degree) for Pure PU,

CTAB-mont, ODA-mont, CATB-mont-PU and ODA-mont-PU 112

4.2. Assigments of the Absorption Bands in FT-IR Spectra of

Polyurethane (mofied from Seymour, et al., 1970 ; Tien Y.I

and Wei K.H., 2001 and Dai, X et al., 2004 ) 115

4.3. Absorption of carbonyl and degree of phase separation 116

4.4. The number-average molecular weight and mechanical

properties of Pure PU and PU/clay nanocomposites 117

4.5 Measured tensile modulus E for Pus-clay nanocomposites 120

4.6 A summary of the kinetics parameters obtained using the simple

linear regression method 128

xi

TABLE OF CONTENTS

Page

DEDICATION ii

ABSTRACT iii

ABSTRAK v

ACKNOWLEDGEMENTS vii

APPROVAL viii

DECLARATION x

LIST OF TABLE xiv

LIST OF FIGURES xv

LIST OF ABBREVIATIONS xxi

CHAPTER

I. INTRODUCTION

1.1 Background 1

1.2 Objectives and Scopes of Work 9

II. LITERATURE REVIEW

2.1 Introduction 12

2.2 Polyurethanes History 13

2.3 Polyurethane Elastomers 17

2.3.1 Definitions 18

2.3.2 Chemistry of polyurethane (PUR)

Elastomers 19

2.4 Polyols from Natural Oils for the

Manufacture of Polyurethanes 36

2.4.1 Synthesis of Polyols based on Palm Oil 36

2.5 Preparation Methods for Polyurethane 38

2.5.1 Solvent-free reactions 38

2.6 Structure and Physical Properties

of Polyurethane Elastomers 42

2.6.1 Phase separation in segmented polyurethane 42

2.6.2 Mechanical properties of polyurethane:

The effect of structure on tensile strength 44

2.7 Market and application of Polyurethanes 44

2.8 Applications of polyurethanes 46

2.9 Synthesis of Polyurethane based on Palm Oil

Polyols 46

2.10 Polyurethane/ Clay nanocomposites 48

2.10.1 Structure of organically modified

layered silicate 49

xii

2.10.2 Types of nanocomposites 53

2.11 Characterization techniques of nanocomposites 54

2.11.1 X-ray diffraction (X-RD) 55

2.12 Nanocomposites preparation 57

2.13 Nanocomposites properties 59

2.13.1 Mechanical properties 59

2.13.2 Thermal stability 70

2.14 Kinetic study of thermal degradation 77

III. METHOD FOR DEVELOPMENT EXPERIMENTAL

3.1 Introduction 79

3.2 Materials 79

3.3. Synthesis of polyol base on palm oil 80

3.4 Preparation of Thermoplastic

Polyurethane Elastomers (TPU) 81

3.5 Preparation of Organophilic Clays 82

3.6 Preparation of Polyurethane/

Clay Nanocomposites 84

3.7 Characterization Techniques 85

3.7.1 Gel Permeation Chromatography (GPC) 86

3.7.2 Fourier Transform Infrared Spectra (FTIR) 87

3.73 X-ray diffraction (X-RD) 89

3.7.3 Dynamic mechanical Analysis(DMA) 89

3.7.5 Tensile properties 90

3.7.6 Modeling Young’s Modulus

of Polyurethane/Clay Nanocomposites 92


3.7.8 Kinetic Studies 95

3.7.9 Scanning Electron Microscopy 98

3.7.10 Transmission Electron Microscopy 98

IV RESULT AND DISCUSSIONS

4.1 Synthesis of polyurethane based on

palm oil polyol 100

4.1.1 FTIR Spectroscopy Analysis 101

4.1.2 Molecular Weight 103

4.2 Preparation of untreated clay to be

clay nanocomposites with difference

surfactants i.e. Cetyl trimethyl ammonium

Bromide (CTAB) and Octadecylamines (ODA) 107

4.3 Synthesis of polyurethane based on palm oil polyol

as metric with clay nanocomposites as reinforcement 109

4.3.1 WAXD curves 109

4.3.2 FTIR Spectra 113

4.3.3 Molecular weight (MW) 117

4.3.4 Mechanical properties 118

xiii

4.3.5 Modeling Young’s Modulus of Polyurethane/

Clay nanocomposites 120


4.3.7 Kinetic study on thermal degradation of

PU/Clay nanocomposites 127

4.3.8 Scanning Electron Microscopy (SEM) 132

4.3.9 Transmission Electron Microscopic (TEM) 135

V CONCLUSION 139

VI RECOMMENDATIONS 143

REFERENCES 145

BIODATA OF THE STUDENT 159

LIST OF PUBLICATIONS 160

AWARDS 161

PUBLICATIONS 163

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