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UNIVERSITI PUTRA MALAYSIA
SYNTHESIS AND CHARACTERIZATION OF SAGO STARCH ESTERS AND THEIR BLENDS WITH
POLY(VINYL CHLORIDE)
SEE YAW KOON
FS 2007 29
SYNTHESIS AND CHARACTERIZATION OF SAGO
STARCH ESTERS AND THEIR BLENDS WITH
POLY(VINYL CHLORIDE)
SEE YAW KOON
MASTER OF SCIENCE
UNIVERSITI PUTRA MALAYSIA
2007
SYNTHESIS AND CHARACTERIZATION OF SAGO
STARCH ESTERS AND THEIR BLENDS WITH
POLY(VINYL CHLORIDE)
By
SEE YAW KOON
Thesis Submitted to the School of Graduate Studies, Universiti Putra
Malaysia, in Fulfilment of the Requirements for the Degree of
Master of Science
February 2007
To my beloved parent, wife and daughter, for their support
and patience with this thesis.
To my sister and brother in law;
to my niece and bother, and to all the others.
See Y. K.
Abstract of thesis presented to the Senate of Universiti Putra Malaysia in
fulfilment of the requirement for the degree of Master of Science
SYNTHESIS AND CHARACTERIZATION OF SAGO STARCH ESTERS
AND THEIR BLENDS WITH POLY(VINYL CHLORIDE)
By
SEE YAW KOON
February 2007
Chairman: Professor Dzulkefly Kuang Abdullah, PhD
Faculty: Science
Esterifying of palm oil based oleochemicals like hexanoyl, octanoyl and lauroyl
chloride onto dried sago starch by using formic acid as an initiator had been
studied in the absence of an organic solvent. A stream of nitrogen gas had been
used to eliminate the hydrochloric acid produced by the reaction. The optimum
conditions in esterifying of starch hexanoate, starch octanoate and starch lauroate
had been studied based on the highest percentage of the recuperation yield.
About 89% of starch hexanoate, 86% of starch octanoate and 80% of starch
lauraote were obtained under optimized conditions with the degree of
substitution (DS) of 1.3, 1.2 and 1.2 respectively. Esterification was evidenced
by the presence of ester carbonyl peak in Fourier transform infrared (FT-IR) and
1H nuclear magnetic resonance (
1H-NMR). The ester group was found to act like
an internal plasticizer because of the reduction of hydrogen bonds between the
starch molecules. The DS of starch esters was determined by elemental analysis.
The TGA had shown that the prepared starch esters had higher thermal stability
than native starch and increased with the increasing of side-chain length and DS.
The DSC thermograms of esterified sago starch showed the depression of glass
transition temperature (Tg) from shorter side-chain length starch ester (starch
hexanoate, 85 oC) to longer side-chain length starch ester (starch lauroate, 36
oC).The mechanical properties of starch esters were determined. Starch lauroate
with the longest side chain length had measurable tensile strength (11.6 ± 0.5
MPa) and elongation at break (2.4 ± 0.3 %) properties compared to starch
hexanoate, starch octanoate and native starch. Tensile strength and elongation at
break depended on the side-chain length and the DS.
Starch hexanoate, starch octanoate and starch lauroate were blended with
poly(vinly chloride) (PVC) at various proportions by using conventional solvent-
casting technique. The FT-IR analysis showed that there were no intermolecular
interactions between starch esters and PVC in room temperature. Thermal and
mechanical properties, water absorption and biodegradation were investigated as
a function of blend composition. The existence of starch esters had enhanced the
thermal properties of PVC and increased with the increasing of starch ester
content. For all blends, the mechanical properties (tensile strength and elongation
at break) retained satisfactory up to 20 wt % for starch ester content. The higher
the content of starch esters was the greater the decreased of mechanical
properties. The blends had shown a minimal water uptake (< 4 wt %) even at the
highest starch ester content (70%). The extent of their biodegradability, after
exposure to sludge, was assessed by weight loss measurements. It was found that
the blends were biodegradable, and the biodegradation rate decreased with
increasing DS.
Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia sebagai
memenuhi keperluan untuk ijazah Master Sains
SINTESIS DAN PENCIRIAN ESTER KANJI SAGU DAN
CAMPURANNYA DENGAN POLI(VINIL KLORIDA)
Oleh
SEE YAW KOON
Februari 2007
Pengerusi: Profesor Dzulkefly Kuang Abdullah, PhD
Fakulti: Sains
Mengester oleokimia asas minyak sawit seperti heksanoil, octanoil dan lauroil
klorida keatas kanji sagu yang kering dengan menggunakan asid formik sebagai
pemula telah dikaji dalam ketidakhadiran sebarang larutan organik. Satu aliran
gas nitrogen telah diguna untuk menyingkir asid hidroklorik yang terhasil oleh
tindak balas. Keadaan-keadaan optimum dalam mengester kanji heksanoat, kanji
oktanoat dan kanji lauroat telah dikaji berdasarkan kepada peratusan hasil
pemulihan yang tertinggi. Kira-kira 89% kanji heksanoat, 86% kanji octanoat
and 80% kanji lauroat telah diperolehi di bawah keadaan-keadaan teroptimum
dengan darjah penggantian (DS) 1.3, 1.2 and 1.2 masing-masing. Pengesteran
telah terbukti oleh kehadiran puncak karbonil ester dalam inframerah Fourier
Transform (FT-IR) dan 1H resonan magnetik nuklear (
1H-NMR). Kumpulan
ester telah dijumpai bertindak selaku bahan plastik dalaman sebab ia
mengurangkan ikatan hidrogen antara molekul kanji. DS ester kanji telah
ditentukan dengan analisis pengunsuran. TGA telah menunjukkan bahawa ester-
ester kanji yang tersedia mempunyai kestabilan terma yang lebih tinggi daripada
kanji semula jadi dan meningkat dengan peningkatan kepanjangan rantai sisi dan
DS. Termogram DSC bagi kanji sagu yang terester menunjuk penurunan suhu
peralihan kaca (Tg) dari ester kanji yang lebih pendek rantai sisi (kanji heksanoat,
85 oC) kepada ester kanji yang lebih pangjang rantai sisi (kanji lauroat, 36
oC) .
Sifat-sifat mekanikal ester-ester kanji telah ditentu. Kanji lauroat dengan
kepanjangan rantai sisi yang terpanjang mempunyai sifat-sifat kekuatan tegangan
(11.6 ± 0.5 %) dan perpanjangan pada putus (2.4 ± 0.3 %) yang boleh diukur
berbanding dengan kanji hexanoat, kanji octanoat dan kanji asal. Kekuatan
tegangan dan perpanjangan pada putus bergantung kepada kepanjangan rantai
sisi dan DS.
Kanji heksanoat, kanji oktanoat dan kanji lauroat telah dicampur dengan
poli(vinil klorida) (PVC) pada pelbagai nisbah dengan menggunakan teknik
pembalutan larutan yang biasa. Analysis FT-IR menunjukkan bahawa tiada
interaksi antara molekul di antara ester kanji dan PVC dalam suhu bilik. Sifat-
sifat terma dan mekanikal, penyerapan air, dan biodegradasi telah dikaji sebagai
fungsi komposisi campuran. Kehadiran ester kanji telah menambah sifat-sifat
terma PVC dan meningkat dengan peningkatan kandungan ester kanji. Bagi
semua campuran, sifat-sifat mekanikal (kekuatan tegangan dan perpanjangan
pada putus) adalah kekal sehingga 20 wt % kandungan ester kanji. Semakin
tinggi kandungan ester-ester kanji, semakin kurang sifat-sifat mekanikalnya.
Campuran-campuran telah menunjukkan pengambilan air yang minimal (< 4 wt
%) walaupun pada kandungan ester kanji yang tertinggi (70%). Takat
kebolehdegradasinya, selepas dedahkan kepada lumpur, telah dinilai dengan
pengukuran kehilangan berat. Adalah didapati bahawa campuran-campuran
adalah boleh dibiodegradasi, dan kadar biodegradasi berkurangan dengan
peningkatan DS.
ACKNOWLEDGEMENTS
First and foremost, I would like to express my deepest gratitude and appreciation
to my supervisor, Professor Dr. Dzulkefly Kuang Abdullah and members of the
supervisory committee, Professor Dr. Anuar Kassim and Associate Professor Dr.
Abdul Halim Abdullah for their advices, caring, guidance and patience
supervision throughout the duration of the study.
I owe my parent, wife and daughter much gratitude for their love and support.
These are the strength that cheers me up throughout this study. I would like to
take this opportunity to express my deepest appreciation to the staffs of the
Chemistry Department of UPM, Kak. Rus, En. Ismail, En. Zainal, En. Kamal,
Kak. Dina and En. Abas for their co-operation and help during the study.
I would like to give a huge thank you to my friends Chee Siong, Azizul, Sooi
Kim and Azri, for they are always standing by to offer their constructive
comments and sharing their knowledge with me. To my housemates Kevin, Chee
Cherng, Yin Seng, Chiang Seng and Chong Boon for all the moral support.
I would like to acknowledge the Ministry of Science, Technology and Innovation
of Malaysia for funding this research through IRPA research grant. Thanks to all
whom might have neglected their names that helped to make this study possible.
I certify that an Examination Committee has met on 13rd
February 2007 to
conduct the final examination of See Yaw Koon on his Master of Science thesis
entitled “Synthesis and Characterization of Sago Starch Esters and Their Blends
with Poly(Vinyl Chloride)” in accordance with Universiti Pertanian Malaysia
(Higher Degree) Act 1980 and Universiti Pertanian Malaysia (Higher Degree)
Regulations 1981. The Committee recommends that the candidate be awarded
the relevant degree. Members of the Examination Committee are as follows:
Md. Jelas Haron, PhD
Professor
Faculty of Science
Universiti Putra Malaysia
(Chairman)
Mohd Zaizi Desa, PhD
Associate Professor
Faculty of Science
Universiti Putra Malaysia
(Internal Examiner)
Mohamad Zaki Ab. Rahman, PhD
Associate Professor
Faculty of Science
Universiti Putra Malaysia
(Internal Examiner)
Hamdan bin Suhaimi, PhD
Professor
Faculty of Science and Technology
Universiti Malaysia Terengganu
(External Examiner)
______________________________
HASANAH MOHD GHAZALI, PhD
Professor/Deputy Dean
School of Graduate Studies
Universiti Putra Malaysia
Date:
This thesis 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 are as follows:
Dzulkefly Kuang bin Abdullah, PhD
Professor
Faculty of Science
Universiti Putra Malaysia
(Chairman)
Anuar bin Kassim, PhD
Professor
Faculty of Science
Universiti Putra Malaysia
(Member)
Abdul Halim bin Abdullah, PhD
Associate Professor
Faculty of Science
Universiti Putra Malaysia
(Member)
______________________
AINI IDERIS, PhD
Professor/Dean
School of Graduate Studies
Universiti Putra Malaysia
Date: 14 JUNE 2007
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 UPM
or other institutions.
________________
SEE YAW KOON
Date: 31 August 2007
TABLE OF CONTENTS
Page
DEDICATION ii
ABSTRACT iii
ABSTRAK v
ACKNOWLEDGEMENTS viii
APPROVAL ix
DECLARATION xi
LIST OF TABLES xv
LIST OF FIGURES xvii
LIST OF ABBREVIATIONS xx
CHAPTER
1 INTRODUCTION
1.1 General Review 1
1.2 Justification of the Study 2
1.3 Objectives of the Study 4
2 LITERATURE REVIEW
2.1 Starch 5
2.1.1 Molecular Structure 5
2.1.2 Starch Granule and Its Properties 8
2.1.3 Applications and Importance of Starch 9
2.2 Sago Palm (Metroxylon spp.) 11
2.3 Sago Starch 13
2.3.1 Molecular Structure and Starch Granule 14
2.3.2 Properties of the Sago Starch 15
2.3.3 Utilization of Sago Starch in Malaysia 15
2.4 Plastics 17
2.4.1 Classification of Plastics 19
2.4.2 Properties of Plastics 20
2.5 Poly(vinyl Chloride) (PVC) 26
2.5.1 Production of PVC 27
2.5.2 Properties and Its Uses 28
2.6 Oleochemicals 31
2.6.1 Palm Oil Based Oleochemicals 32
2.7 Modification of Starch 35
2.7.1 Starch Chemical Modification –
Esterification
37
2.8 Biodegradation 40
2.9 Starch – Polymer Blends 42
2.10 Suitability of Sago Starch to Produce Starch Esters
and Plastic Materia
44
2.10.1 Quality 44
2.10.2 Particle Size 45
2.10.3 Thermal Stability 46
3 METHODOLOGY
3.1 Materials 47
3.2 Synthesis of Starch Esters 47
3.2.1 Optimization of Esterification 49
3.2.2 Determination of the Degree of Substitution
(DS)
49
3.2.3 Analysis of the Starch Esters by FT-IR
Spectroscopy
50
3.2.4 Analysis of the Starch Esters by 1H NMR
Spectroscopy
50
3.2.5 Thermal Analysis of the Starch Esters 50
3.2.6 Mechanical Properties of the Starch Esters 51
3.3 Preparation of Starch Esters/Poly(vinyl chloride)
Blend Films
52
3.3.1 Thickness Measurements 53
3.3.2 Analysis of Starch Esters/PVC Blends by
FT-IR Spectroscopy
53
3.3.3 Thermal Analysis of Starch Esters/PVC
Blends
53
3.3.4 Mechanical Properties of Starch Esters/
PVC Blends
54
3.3.5 Water Absorption of Starch Esters/PVC
Blends
54
3.3.6 Biodegradation of Starch Esters/PVC
Blends
55
4 RESULTS AND DISCUSSION
4.1 Esterification 56
4.1.1 Optimization of Esterification 58
4.1.2 Determination of Degree of Substitution
(DS) of Starch Esters
66
4.1.3 FT-IR Analysis of Starch Esters 68
4.1.4 1H NMR Analysis of Starch Esters 70
4.1.5 Thermal Properties Analysis of Starch
Esters
73
4.1.6 Mechanical Properties of the Starch Esters 78
4.2 Starch Esters/Poly(vinyl chloride) Blend Films 79
4.2.1 FT-IR Analysis of Blends 81
4.2.2 Thermal Analysis of Blends 83
4.2.3 Mechanical Properties of Blends 90
4.2.4 Water Absorption of Starch Esters/ PVC
Blends
94
4.2.5 Biodegradation of Starch Esters/PVC
Blends
98
5 CONCLUSION
5.1 Conclusion 102
5.2 Recommendation for Further Studies 104
REFERENCES 107
APPENDICES 114
BIODATA OF THE AUTHOR 119
LIST OF TABLES
Table Page
2.1 Ratio between amylose and amylopectin of different starches 8
2.2 Representative properties of commercial grade of PVC 29
2.3 Comparison the production of palm oil based oleochemicals
between Malaysia and world
34
2.4 Fatty acid chlorides and its properties 36
2.5 Modification of starch 38
4.1(a) Influence of concentration of formic acid (FA) on the
recuperation yield (RY) and DS of starch hexanoate (6
eq/glucose of hexanoyl chloride, 40 minutes of reaction time
and 90 oC of reaction temperature)
59
4.1(b) Influence of concentration of formic acid (FA) on the
recuperation yield (RY) and DS of starch octanoate (3
eq/glucose of octanoyl chloride, 40 minutes of reaction time
and 90 oC of reaction temperature)
59
4.1(c) Influence of concentration of formic acid (FA) on the
recuperation yield (RY) and DS of starch lauroate (3.4
eq/glucose of lauroyl chloride, 40 minutes of reaction time and
90 oC of reaction temperature)
59
4.2(a) Influence of the concentration of hexanoyl chloride (HC) on
the recuperation yield (RY) and DS of starch hexanoate (4.3
eq/glucose of formic acid, 40 minutes of reaction time and 90 oC of reaction temperature)
62
4.2(b) Influence of the concentration of octanoyl chloride (OC) on
the recuperation yield (RY) and DS of starch octanoate (4.3
eq/glucose of formic acid, 40 minutes of reaction time and 90 oC of reaction temperature)
62
4.2(c) Influence of the concentration of lauroyl chloride (LC) on the
recuperation yield (RY) and DS of starch lauroate (4.3
eq/glucose of formic acid, 40 minutes of reaction time and 90 oC of reaction temperature)
62
4.3(a) Influence of the duration of the reaction on the recuperation
yield (RY) and DS of starch hexanoate (4.3 eq/glucose formic
acid, 6.0 eq/glucose of hexanoyl chloride and 90 oC of reaction
temperature)
64
4.3(b) Influence of the duration of the reaction on the recuperation
yield (RY) and DS of starch octanoate (4.3 eq/glucose formic
acid, 3.8 eq/glucose of octanoyl chloride and 90 oC of reaction
temperature)
64
4.3(c) Influence of the duration of the reaction on the recuperation
yield (RY) and DS of starch lauroate (4.3 eq/glucose of formic
acid, 4.0 eq/glucose of lauroyl chloride and 90 oC of reaction
temperature)
64
4.4(a) Influence of the temperature (T) on the recuperation yield
(RY) and DS of starch hexanoate (4.3 eq/glucose formic acid,
6.0 eq/glucose of hexanoyl chloride and 40 minutes of reaction
time)
65
4.4(b) Influence of the temperature (T) on the recuperation yield
(RY) and DS of starch octanoate (4.3 eq/glucose formic acid,
3.8 eq/glucose of octanoyl chloride and 40 minutes of reaction
time)
65
4.4(c) Influence of the temperature (T) on the recuperation yield
(RY) and DS of starch lauroate (4.3 eq/glucose of formic acid,
4.0 eq/glucose of lauroyl chloride and 40 minutes of reaction
time)
65
4.5 Optimum conditions for esterification of sago starch 66
4.6 Determination of DS of the starch esters 67
4.7 Mechanical properties of fatty sago starch esters 79
LIST OF FIGURES
Figure Page
2.1 Linear and branched starch polymers 6
2.2 Starch granules 9
2.3 Trunk of sago 12
2.4 Granule structure of sago starch 14
2.5 Mechanical properties testing of thin plastic sheet 22
2.6 A possible of DSC curve 24
2.7 Residual mass, Mres and oxidation temperature (To) 26
2.8 The production of poly(vinyl chloride) 28
2.9 Scheme of dehydrochlorination of PVC 30
2.10 Hydrolysis of 1 mole triglyceride to form 1 mole glycerol
and 3 moles fatty acids
34
2.11 The preparation of fatty acid chloride from palm oil based
fatty acid
34
2.12 Chemical and biochemical modifications of starch 38
3.1 Dimensions of sample 51
4.1 Esterification of sago starch by fatty acid chloride in the
presence of formic acid
57
4.2 The conversion of sago starch to starch ester 58
4.3 FT-IR spectra of (a) sago starch, (b) and (c) are esterified
sago starch with DS 0.6 and 1.2 respectively
69
4.4 FT-IR spectra of starch (a) hexanoate, (b) octanoate and (c)
lauroate with DS 1.3, 1.2 and 1.2 respectively
71
4.5 NMR spectra of (a) sago starch and (b) esterified sago
starch
72
4.6 TGA thermograms of (a) sago starch, starch (b) lauroate
with DS 0.6, (c) hexanoate, (d) octanoate and (e) lauroate
with DS 1.3, 1.2 and 1.2 respectively
74
4.7 DSC thermogram of native sago starch 76
4.8 DSC thermograms of starch (a) hexanoate, (b) octanoate
(c) lauroate with DS 1.3, 1.2 and 1.2 respectively
76
4.9 The appearance of pure PVC film and starch ester/PVC
blend film
80
4.10 FT-IR spectra of (a) starch lauroate DS 1.3, (b) starch
lauroate/PVC of 50/50 blends and (c) PVC
82
4.11 TGA thermograms of PVC, starch hexanoate (DS 1.3) and
starch hexanoate DS 1.3/PVC blends
84
4.12 TGA thermograms of PVC, starch octanoate (DS 1.2) and
starch octanoate DS 1.2/PVC blends
84
4.13 TGA thermograms of PVC, starch lauroate (DS 1.2) and
starch lauroate DS 1.2/PVC blends
85
4.14 TGA thermograms of 50/50 of starch esters/PVC blends
and pure PVC
85
4.15 DSC thermograms of PVC and starch hexanoate DS
1.3/PVC blends
87
4.16 DSC thermograms of PVC and starch octanoate DS
1.2/PVC blends
87
4.17 DSC thermograms of PVC and starch lauroate DS 1.2/PVC
blends
88
4.18 DSC thermograms of 70/30 of starch esters/PVC blends
and pure PVC
88
4.19 Tensile strength at break of blends of starch lauroate DS
0.6 (STLC0.6), starch hexanoate DS 1.3 (STHC1.3), starch
octanoate DS 1.2 (STOC1.2) and starch lauroate DS1.2
(STLC1.2) with PVC
91
4.20 Relative tensile strength of blends of starch lauroate DS 0.6
(STLC0.6), starch hexanoate DS 1.3 (STHC1.3), starch
octanoate DS 1.2 (STOC1.2) and starch lauroate DS 1.2
(STLC1.2) with PVC
91
4.21 Elongation at break of blends of starch lauroate DS 0.6
(STLC0.6), starch hexanoate DS 1.3 (STHC1.3), starch
octanoate DS 1.2 (STOC1.2) and starch lauroate DS 1.2
(STLC1.2) with PVC
93
4.22 Relative elongation at break of blends of starch lauraote
DS 0.6 (STLC0.6), starch hexanoate DS 1.3 (STHC1.3),
starch octanoate DS 1.2 (STOC1.2) and starch lauroate DS
1.2 (STLC1.2) with PVC
93
4.23 Water absorption versus time of starch hexanoate DS
1.3/PVC blends
95
4.24 Water absorption versus time of starch octanoate DS
1.2/PVC blends
95
4.25 Water absorption versus time of starch lauroate DS
1.2/PVC blends
96
4.26 Water absorption of 50/50 of starch hexanoate DS 1.3/PVC
(STHC1.3), starch octanoate DS 1.2/PVC (STOC1.2),
starch lauroate DS 1.2/PVC (STLC1.2) and starch lauroate
DS 0.6 (STLC0.6)/PVC blends and pure PVC
96
4.27 Weight loss of starch hexanoate DS 1.3/PVC blends during
immersion in sludge
99
4.28 Weight loss of starch octanoate DS 1.2/PVC blends during
immersion in sludge
99
4.29 Weight loss of starch lauroate DS 1.2/PVC blends during
immersion in sludge
100
4.30 Weight loss of 50/50 of starch hexanoate DS 1.3/PVC
(STHC1.3), starch octanoate DS 1.2/PVC (STOC1.2),
starch lauroate DS 1.2/PVC (STLC1.2) and starch lauroate
DS 0.6/PVC (STLC0.6) blends and pure PVC
100
LIST OF ABBREVIATIONS
ASTM The American Society for Testing and Materials
CPKO Crude palm kernel oil
CPO Crude palm oil
DS Degree of substitution
DSC Differential Scanning Calorimeter
DMSO Dimethyl sulfoxide
EDC Ethylene dichloride
et al. et alia (and others)
FT-IR Fourier Transform Infrared
GPa Giga pascal
ha Hectare
HCl Hydrochloric acid
LDPE Low density polyethylene
Mpa Mega pascal
Mres Residual mass
NMR Nuclear Magnetic Resonance
psi Pounds per square inch
PVC Poly(vinly chloride)
spp. Species (more than one)
t Time
T Temperature
Td Decomposition temperature
Tg Glass transition temperature
TGA Thermogravimetric analysis
THF Tetrahydrofuran
Tm Melt transition temperature
To Oxidation temperature
VC Vinyl chloride
wt % Percentage of weight
> More than
< Less than
CHAPTER 1
INTRODUCTION
1.1 General Review
Today, plastic industries are concerning about the biodegradability of their
petroleum-based products before bring them to the market place. Virtually no
synthetic plastic is totally biodegradable. It is highly resistant to microbial attack
and is the major cause of the environmental problems. Replacement of synthetic
plastics with materials from agro resources, especially starch, is attractive
because of providing biodegradation properties.
However, starch by itself is unsuitable for most uses as a plastic because of its
poor physical and chemical properties. Some approaches to overcoming these
problems include physical and chemical modifications. For example, long chain
esters of starch with high degree of substitution (DS) from chemical modification
have interesting thermoplastic properties (Aburto et al., 1999a).
Actually, utilization of modified starch in the plastics industry is not new.
Interest in the preparation of chemically or physically modified starches remains
high (Aburto et al., 1999a; Kiatamjornwong et al., 2001; Sang and Lim, 1998)
despite the fact that the vast majority of commercially available modified
starches today are based on the work carried out in the 1940s and 1950s (Fang et
al., 2002).
1.2 Justification of the Study
Biodegradable plastics offer a solution to the growing disposal problem of
petroleum-based plastics. The greatest part of the plastic waste derived from
packaging and building constructions for which recycling are neither practical
nor economical. The choices for dealing with this waste are limited as
incineration of plastic polymers results in the generation of toxic emissions; the
only viable solution is to bury the material in landfills. However, this approach is
also limited because of the resistant nature of plastic to biological degradation.
So, the productions of biodegradable starch plastics are desirable.
Substitution of petroleum based plastics with starch plastic would permit us to
conserve our petrochemical resources and to find out new non-food uses for
starch. Starch is inexpensive, abundance and is produced in greater quantities
than current market demand (Shogren et al., 1993).
Biodegradable starch plastics can be prepared in numerous ways include
chemical and physical means. One of the chemical modifications is
esterification. Lipophilic substitution of hydroxyl groups of starch with alkyl
groups in organic solvent medium has produced starch ester. High degree
substitution of starch esters behaves as thermoplastic properties, but their high