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UNIVERSITI PUTRA MALAYSIA

CHARACTERIZATION OF NANOCOMPOSITES BASED ON PLASTICIZED STARCH AND KENAF BAST NANOFIBERS

SAMANEH KARIMIMAZRAEHSHAHI

IPTPH 2014 1

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CHARACTERIZATION OF NANOCOMPOSITES BASED ON

PLASTICIZED STARCH AND KENAF BAST NANOFIBERS

By


Thesis Submitted to the School of Graduate Studies, Universiti Putra

Malaysia, in Fulfillment of the Requirements for the Degree of Doctor of

Philosophy

January 2014

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COPYRIGHT

All material contained within the thesis, including without limitation text, logos,

icons, photographs and all other artwork, is copyright material of Universiti Putra

Malaysia unless otherwise stated. Use may be made of any material contained

within the thesis for non-commercial purposes from the copyright holder.

Commercial use of material may only be made with the express, prior, written

permission of Universiti Putra Malaysia.

Copyright © Universiti Putra Malaysia

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DEDICATION

I dedicate this dissertation to my wonderful family who surrounds me with

unconditional LOVE.

Especially to:

My lovely husband, Mehdi, who is always pushing me forward and is the source

of energy, inspiration and courage.

My uncle, Professor Ali, who without his encouragements, sacrifices and support

this work was not possible.

My terrific parents, Ashraf & Hassan, who are the source of love and compassion.

I never would have made it here without you!

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

fulfilment of the requirement for the degree of Doctor of Philosophy

CHARACTERIZATION OF NANOCOMPOSITES BASED ON

PLASTICIZED STARCH AND KENAF BAST NANOFIBERS

By


January 2014

Chair: Professor Paridah Md. Tahir, PhD

Institute: Institute of Tropical Forestry and Forest Products

Plants cell walls are biological nanocomposites which exhibit high mechanical

properties at a light weight. The secret of this rigidity and strength lies in its main

structural component; cellulose. Native cellulose exists as highly-ordered

microfibrils, which are just a few nanometers wide and have been found to be

stiffer than many synthetic fibers. Many critical issues associated with global

warming, environmental pollution and the amount of plastic wastes, synergistic

with the scarcity and non-renewability of petroleum and petroleum-based products

are driving material and composite scientists to focus on development of

renewable and sustainable biomaterials. In this quest, using cellulose microfibrils

from plant materials as renewable alternatives to conventional reinforcement

materials such as glass fibers and carbon fibers is generating particular interest.

Cellulosic nanofibers have the potential to reinforce and enhance properties of

polymeric matrices, significantly, even at very low volume fractions. According to

objectives of this research, by applying a chemi-mechanical approach both

unbleached and bleached cellulose nanofibers were extracted from the cell wall of

kenaf bast fibers and characterized. Then, the reinforcement performances of

these two nanofillers were studied and compared using the starch as a matrix

material, to identify the necessity of bleaching procedures in nanofiber isolation

process. Subsequently, according to result, nanocomposite with different fiber

loadings were prepared with unbleached nanofibers. Structural and mechanical

performances of these materials were studied and compared with the composite

prepared with micro scale cellulosic fibers from kenaf bast, unders the same

conditions, to fully understand the effect of fibers loading and dimension on

properties of fabricated materials.

In order to undertake the research objectives, cellulosic fiber hierarchy from kenaf

bast were isolated in three stages. Initially raw kenaf bast fibers were subjected to

soda-AQ pulping process to eliminate lignin and hemicellulose. Unbleached fibers

then undergone a bleaching process and finally both pulped and bleached fibers

were mechanically separated into their constituent nanoscale cellulosic fibers. The

influence of each treatment on the chemical composition, morphology, functional

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groups, crystallinity, and thermal stability of fibers was investigated. Attenuated

total reflectance Fourier transform infrared spectroscopy (ATR/FTIR) showed that

lignin and hemicellulose were almost entirely removed during the alkali and

bleaching treatments. Morphological studies of fiber hierarchy were done by

scanning electron microscopy (SEM) and transmission electron microscopy

(TEM). X-Ray diffraction (XRD) analysis revealed that the crystallinity of fibers

increased from 62.9 to 81.5% as subsequent treatments were applied. Comparison

with other works demonstrated the effectiveness and superior yield of 62.5% for

unbleached nanofibers and 58% for bleached nanofibers, in the applied approach

for producing nanocellulose from kenaf bast fibers. The isolated nanofibers

displayed about 10% enhancement in thermal stability compare to that of raw

kenaf bast fiber. The results of study on the properties of isolated bleached and

unbleached nanofibers indicated the probable redundancy of the bleaching process

as no significant difference was observed in their characteristics.

The surface chemistry of the unbleached and bleached nanofibers is different and

it has led to different behavior when these nanofibers are incorporated into

polymeric matrices. In order to evaluate this issue both types of nanofibers were

used to reinforce thermoplastic starch matrix and properties of obtained

nanocomposite films were characterized using SEM, ATR/FTIR, XRD,

thermogravimetric analysis (TGA), tensile and water uptake experiments. The

results showed superior overall performance of nanocomposite films made from

unbleached nanofibers. Thus the redundancy of bleaching procedures in nanofiber

isolation process was cleared.

In the subsequent work, unbleached nanofibers with different loading (0-10 wt%)

were incorporated into thermoplastic starch matrix. Thin bionanocomposite films

were made by casting and evaporating the mixture of aqueous suspension of

nanofibers, starch and glycerol which underwent gelatinization process at the

same time. In order to elucidate the importance and the effect of nanoscale

cellulosic fibers on the performance of fabricated materials, starch based

composite films with the exact same conditions were made by using micro sized

pulverized kenaf bast fibers. The resulting composite and nanocomposite films

were characterized by SEM, TEM, ATR/FTIR, XRD, TGA, scanning differential

calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), tensile and

water uptake experiments. Among tested materials, the nanoreinforced composites

had significantly greater performance, particularly; increased mechanical strength

and reduced water sensitivity. Tensile strength and Young’s modulus increased by

313% and 343% and water uptake reduced by 21% with addition of 10%

nanofibers. Overalls results demonstrated that applied nanofibers strongly

interacted by hydrogen bonding with the starch matrix and showed a favourable

compatibility which can be attributed to their chemical similarities.

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Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia

Sebagai memenuhi keperluan untuk ijazah Doktor Falsafah

PENCIRIAN NANOKOMPOSIT BERDASARKAN DIPLASTIKKAN

KANJI DAN KENAF BAST NANOFIBERS

Oleh


Januari 2014

Pengerusi: Professor Paridah Md. Tahir, PhD

Institut: Institut Perhutanan Tropika dan Produk Hutan

Dinding sel tumbuhan nanokomposit biologi yang menunjukkan sifat-sifat

mekanik yang tinggi pada berat cahaya. Rahsia ketegaran dan kekuatan terletak

kepada komponen utamanya iaitu struktur selulosa.Selulosa asli microfibrils yang

wujud sangat tinggi, yang mempunyai luas hanya beberapa nanometer telah

didapati lebih keras daripada banyak serat sintetik. Banyak isu-isu kritikal yang

berkaitan dengan pemanasan global, pencemaran alam sekitar dan jumlah sisa

plastik, yang disinergi dengan kekurangan dan petroleum yang tidak diperbaharui

dan produk berasaskan petroleum dalam pembangunan bahan komposit dan

saintis memberi tumpuan kepada pembangunan biobahan yang boleh diperbaharui

dan mudah diperolehi. Dalam usaha ini, dengan menggunakan microfibrils

selulosa dari bahan tumbuhan sebagai alternatif yang boleh diperbaharui kepada

bahan-bahan pengukuhan konvensional seperti gentian kaca dan gentian karbon

adalah menjana kepentingan tertentu. Nanofibers Cellulosic mempunyai potensi

untuk mengukuh dan meningkatkan sifat-sifat matriks polimer, dengan ketara,

walaupun pada pecahan jumlah yang sangat rendah. Menurut objektif kajian ini,

dengan menggunakan pendekatan bahan- mekanikal kedua-dua luntur dan

terluntur nanofibers selulosa dipetik daripada dinding sel kenaf fibers. Kemudian,

prestasi pengukuhan kedua-dua nanofillers telah dikaji dan dibandingkan

menggunakan kanji sebagai bahan matriks, untuk mengenal pasti keperluan

prosedur pelunturan dalam proses pengasingan nanofiber. Selepas itu, menurut

hasil, nanocomposite dengan bebanan gentian yang berbeza telah disediakan

dengan nanofiber luntur. Prestasi struktur dan mekanikal bahan-bahan ini telah

dikaji dan dibandingkan dengan komposit yang disediakan dengan skala mikro

serat cellulosic dari kenafbast, dalam keadaan yang sama, untuk memahami

sepenuhnya kesan serat memuatkan dan dimensi pada sifat bahan fabrikasi.

Dalam kajian ini, hirarki gentian selulosa dari kulit kenaf telah diasingkan dalam

tiga peringkat yang berbeza. Gentian kulit kenaf mentah pada mulanya telah

melalui proses pempulpaan untuk mengasingkan lignin dan hemiselulosa. Setelah

mendapatkan gentian daripada pulpa, ia melalui proses pelunturan dan akhirnya

kedua-dua gentian pulpa dan gentian yang telah dilunturkan diasingkan secara

mekanikal kepada konstituen gentian selulosa berskalanano. Kesan setiap rawatan

terhadap kandungan kimia, morfologi, kumpulan fungsi, kristaliniti, dan

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kestabilan haba gentian telah dikaji. Jumlah pantulan lemah spektroskopi

(ATR/FTIR) menunjukkan bahawa hampir semua lignin dan hemiselulosa telah

dikeluarkan semasa rawatan alkali dan pelunturan. Kajian morfologi terhadap

hierarki gentian telah dijalankan menggunakan mikroskop electron pengimbas

(SEM) dan mikroskop electron transmisi (TEM). X-Ray pembelauan (XRD) pula

menunjukkan bahawa kristaliniti fiber meningkat dari 62.9-81.5% selepas setiap

rawatan yang digunakan. Perbandingan dengan rawatan yang lain menunjukkan

keberkesanan dan hasil melebihi 62.5% bagi nanofibers luntur dan 58% untuk

nanofiber terluntur, dalam pendekatan yang digunakan untuk penghasilan nano

sellulose dari kenaf fiber. Hasil daripada rawatan ini nano fiber yang terpencil

menunjukkan peningkatan kira-kira 10% dalam kestabilan terma berbanding

dengan kenaf fiber yang mentah. Keputusan kajian terhadap sifat luntur terpencil

dan nanofibers luntur menunjukkan lebihan kemungkinan proses pelunturan

sebagai tidak ada kesan yang diperhatikan dalam ciri-ciri mereka.

Walaubagaimanapun, sifat kimia permukaan yang diperoleh daripada gentian

nano yang tidak dilunturkan adalah berbeza dan ia mungkin disebabkan oleh

perlakuan yang berbeza apabila digabungkan kedalam matrik polimer. Dalam

usaha untuk menilai kedua-dua jenis gentian nano yang telah digunakan bagi

memperkukuh matrik kanji termoplastik dan sifat-sifat filem gentian nano, ia telah

dianalisis menggunakan eksperimen SEM, ATR/FTIR, XRD, TGA, kekuatan

tarik, dan penyerapan air. Menariknya, keputusan yang diperoleh oleh filem

komposit nano yang diperbuat daripada gentian nano tidak luntur menunjukkan

prestasi yang lebih baik secara keseluruhannya. Ini adalah hasil kajian yang

bernilai tinggi dan menghapuskan prosedur pelunturan yang berlebihan dalam

proses-proses pengasingan gentian nano.

Dalam usaha untuk membangunkan nano komposit selulosa berasaskan kanji,

gentian nano yang tidak dilunturkan dengan kandungan berlainan (0-10 wt %)

dicampurkan ke dalam matrik kanji termoplastik. Filem bionanokomposit nipis

telah dihasilkan dengan meletakkan dan meruap campuran gentian nanoterampai,

kanji, dangliserol melalui proses pengelatinan dalam masa yang sama. Dalam

usaha untuk menerangkan kepentingan dan kesan gentian selulosa berskalanano,

filem komposit berasaskan kanji dengan keadaan yang sama telah dihasilkan

dengan menggunakan gentian kulit kenaf yang telah dikisar bersaiz mikro.

Komposit dan filem nanokomposit yang terhasil kemudiannya dicirikan

menggunakan eksperimen SEM, TEM, ATR/FTIR, XRD, TGA, DSC, DMTA,

kekuatan tarik, dan penyerapan air. Keputusan yang diperoleh menunjukkan

bahawa antara bahan yang diuji, komposit nano diperkukuh mempunyai sifat yang

lebih baik secara ketara, khususnya; meningkatkan kekuatan mekanikal dan

mengurangkan kepekaan terhadap air. Kekuatan tegangan dan modulus kecil

meningkat sebanyak 313% dan 343% dan penggunaan air dikurangkan sebanyak

21% dengan tambahan sebanyak 10% nanofibers.Hasil kajian menunjukkan

gentian nano gunaan saling bertindak balas secara kuat terhadap ikatan hydrogen

dengan matrik kanji, dan menunjukkan kesesuaian yang disebabkan oleh

persamaan kimia.

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ACKNOWLEDGEMENTS

It is a pleasure to thank the people who made this thesis possible. First of all, I

would like to express my deepest sense of gratitude to my supervisory committee.

Without their help I would not have had the opportunity to work on such a

challenging and valuable project. Many thanks are expressed to Professor Paridah

Md. Tahir for her patience, encouragement and continuous support throughout

this study. Special thanks go to Professor Alain Dufresne for his invaluable

comments, recommendations, kindness and contribution. I am sincerely grateful

for the support and positive attitude of Professor Luqman Chuah Abdullah. I

would like to thank Dr. Ali Abdulkhani who gave me a significant help in

completing this work. I am also grateful to Professor Ali Karimi for his faithful

support and encouragements.

Lots and lots of thanks to all the members of the Institute of Tropical Forestry and

Forest Products, Universiti Putra Malaysia, including staffs and students.

Thanks to dear examiners, which I do not know them, but I want to send my lots

and lots of thanks and respects, for their invaluable time that they allocate to

evaluate this research.

I have spent nice moments in my second country, Malaysia, country of people

from different cultures and religions who live together in peace.

Thanks are also extended to Amirhossein Mehbodnia, Ali Hosseini, Mehdi

Hosseini, and Amin Parvizi. They were there for me during good and bad times,

offering helping hands and being a source of happiness.

I wish to thank my dear brothers, Arash & Afshin, and my sister in-law, Maryam,

for their kindness and support during these years.

Many thanks go to my in-law family for their kindness and prayers, particularly

my dear brother in-law, Mehrdad, for his sincere assistance and online support.

I would like to express my gratitude for the most wonderful part of my life, my

beloved husband, Mehdi, for his unconditional love, encouragement and positive

attitudes.

Last but not the least, I must give very special thanks to my dear uncle and parents

who have taught me to succeed, and for their constant love, patience, calmness,

encouragement and believing me in all these years.

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I certify that a Thesis Examination Committee has met on 24th

January 2014 to

conduct the final examination of Samane Karimimazraehshahi on her thesis

entitled “Characterization of Nanocomposites Based on Plasticized Starch and

Kenaf Bast Nanofibers” 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

Doctor of Philosophy.

Members of the Thesis Examination Committee were as follows:

Mohd Sapuan Bin Salit, PhD

Professor

Faculty of Engineering

Universiti Putra Malaysia

(Chairman)

Azmi Zakaria, PhD

Professor

Faculty of Science


(Internal Examiner)

Azowa Nor Ibrahim, PhD

Doctor

Faculty of Science


(Internal Examiner)

Martin Hubbe, PhD

Professor

Faculty of Natural Resources

North Carolina State University

United States of America

(External Examiner)

_________________________________

NORITAH OMAR, PhD Associate Professor and Deputy Dean

School of Graduate Studies


Date: 10 March 2014

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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 Doctor of Philosophy.

The members of the Supervisory Committee were as follows:

Paridah Md. Tahir, PhD

Professor

Institute of Tropical Forestry and Forest Products


(Chairman)

Luqman Chuah Abdullah, PhD

Professor

Faculty of Engineering


(Member)

Alain Dufresne, PhD

Professor

The International School of Paper, Print Media and Biomaterials

Grenoble Institute of Technology, France

(Member)

Ali Abdulkhani, PhD

Assistant Professor

Faculty of Natural Resources

University of Tehran, Iran

(Member)

_________________________________

BUJANG BIN KIM HUAT, PhD Professor and Dean

School of Graduate Studies


Date: 3 April 2014

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DECLARATION

Declaration by graduate student

I hereby confirm that:

this thesis is my original work;

quotations, illustrations and citations have been duly referenced;

this thesis has not been submitted previously or concurrently for any other

degree at any other institutions;

intellectual property from the thesis and copyright of thesis are fully-

owned by Universiti Putra Malaysia, as according to the Universiti Putra

Malaysia (Research) Rules 2012;

written permission must be obtained from supervisor and the office of

Deputy Vice-Chancellor (Research and Innovation) before thesis is

published (in the form of written, printed or in electronic form) including

books, journals, modules, proceedings, popular writings, seminar papers,

manuscripts, posters, reports, lecture notes, learning modules or any other

materials as stated in the Universiti Putra Malaysia (Research) Rules 2012;

there is no plagiarism or data falsification/fabrication in the thesis, and

scholarly integrity is upheld as according to the Universiti Putra Malaysia

(Graduate Studies) Rules 2003 (Revision 2012-2013) and the Universiti

Putra Malaysia (Research) Rules 2012. The thesis has undergone

plagiarism detection software.

Signature: _______________________ Date: 24 January 2014

Name and Matric No.: Samaneh Karimimazraehshahi (GS24934)

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Declaration by members of supervisory committee

This is to confirm that:

the research conducted and the writing of this thesis was under our

supervision;

supervision responsibilities as stated in the Universiti Putra Malaysia

(Graduate Studies) Rules 2003 (Revision 2012-2013) are adhered to.

Signature: __________________

Name of

Chairman of

Supervisory

Committee: Paridah Md. Tahir, PhD

Signature: __________________

Name of

Member of

Supervisory

Committee: Alain Dufresne, PhD

Signature: __________________

Name of

Member of

Supervisory

Committee: Luqman Chuah Abdullah, PhD

Signature: __________________

Name of

Member of

Supervisory

Committee: Ali Abdulkhani, PhD

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TABLE OF CONTENTS

Page

ABSTRACT Error!

Bookmark not defined.

ABSTRAK Error!


ACKNOWLEDGEMENTS vii

APPROVAL Error!


DECLARATION x

LIST OF TABLES Error!


LIST OF FIGURES Error!


LIST OF ABBREVIATIONS Error!


CHAPTER

1 INTRODUCTION Error!


1.1 Background Error!


1.2 Lignocellulosic materials Error!


1.3 Nanocellulose sources Error!


1.3.1 Wood-based resources Error!


1.3.2 Non-wood crops Error!


1.3.3 Bacterial source Error!


1.4 Nanocellulose isolation techniques Error!


1.4.1 Chemi-mechanical defibrillation Error!


1.4.2 Acid hydrolysis Error!


1.4.3 Enzymatic treatment Error!


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1.5 Nanocomposites processing techniques Error!


1.5.1 Solution Casting Error!


1.6 Problem Statement Error!


1.7 Scope of the study Error!


1.8 Research objectives Error!


1.9 Organization of the thesis Error!


2 LITERATURE REVIEW Error!


2.1 Kenaf from fiber to nanocomposite Error!


2.1.1 A short history of kenaf Error!


2.1.2 Why kenaf Error!


2.1.3 Anatomy and composition of kenaf Error!


2.1.4 Fiber processing Error!


2.1.5 Hierarchical structure: from micro to nano Error!


2.1.6 Kenaf and nanocomposites Error!


2.1.7 Current challenges Error!


2.1.8 Potential applications Error!


2.2 Starch based bionanocomposites Error!


2.2.1. A short history of nanothechnology and nanostructured materials

Error! Bookmark not defined.

2.2.2. Cellulosic nanostructures Error!


2.2.3. Starch based cellulose nanocomposites Error!


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2.3 Summary Error!


3 PREPARATION OF NANOFIBERS FROM KENAF BAST Error!


3.1 Introduction Error!


3.2 Chemical pulping Error!


3.2.1 Why soda-AQ pulping Error!


3.3 Bleaching Error!


3.4 Objectives Error!


3.5 Experimental Error!


3.5.1 Materials Error!


3.5.2 Isolation Processes Error!


3.5.3 Chemical Analysis Error!


3.5.4 Morphological Analysis Error!


3.5.5 Functional Group Analysis Error!


3.5.6 Crystallinity Determination Error!


3.5.7 Thermogravimetric Analysis (TGA) Error!


3.6 Results and discussion Error!


3.6.1 Yields Error!


3.6.2 Chemical Composition Error!


3.6.3 Morphological Analysis Error!


3.6.4 Fourier Transform Infrared (FTIR) Spectroscopy Error!


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3.6.5 Crystallinity Error!


3.6.6 TGA analysis Error!


3.7 Conclusions Error!


4 PROPERTIES OF STARCH BASEDBIONANOCOMPOSITES MADE

FROM BLEACHED AND UNBLEACHED NANOFIBERS




4.2 Objective Error!






4.3.2 Nanofiber isolation Error!


4.3.3 Film casting Error!


4.3.4 Electron microscopy Error!


4.3.5 Attenuated total reflectance Fourier transform infrared

spectroscopy (ATR/FTIR) Error!


4.3.6 X-ray diffraction (XRD) Error!


4.3.7 Thermogravimetric analysis (TGA) Error!


4.3.8 Water uptake Error!


4.3.9 Tensile tests Error!




4.4.1 Morphology Error!


4.4.2 Tensile mechanical properties Error!


4.4.3 Structural Analysis Error!


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4.4.5 Thermogravimetric analysis (TGA) Error!




5 EFFECT OF MICRO AND NANO REINFORCEMENTES ON

MECHANICAL BEHAVIOR OF STARCH BASED COMPOSITES










5.3.2 Nanofiber isolation process Error!


5.3.3 Composite and nanocomposite films processing Error!


5.3.4 Microscopy Error!


5.3.5 Dynamic mechanical thermal analysis (DMTA) Error!


5.3.6 Tensile tests Error!


5.3.7 Statistical analysis Error!




5.4.1 Morphology Error!


5.4.2 Tensile mechanical properties Error!


5.4.3 Dynamic mechanical thermal analysis (DMTA) Error!


5.4.4 Optical transparency Error!




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6 EFFECT OF MICRO AND NANO REINFORCEMENTES ON

STRUCTURAL PROPERTIES OF STARCH BASED COMPOSITES








6.3.1 Nanofiber isolation Error!


6.3.2 Film processing Error!


6.3.3 Microscopy Error!





6.3.5 X-ray diffraction (XRD) Error!


6.3.6 Thermal properties Error!






6.4.1 Morphological characterization Error!


6.4.2 Thermal properties Error!





6.4.4 X-ray diffraction Error!


6.4.5 Water Uptake Error!




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7 OVERALL CONCLUSIONS AND RECOMMENDATIONS FOR

FUTURE STUDIES Error! Bookmark

not defined.



7.2 Recommendations for future research Error!


REFERENCES Error!


BIODATA OF STUDENT Error!


LIST OF PUBLICATIONS DURING CANDIDATURE Error!


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