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UNIVERSITI PUTRA MALAYSIA
SYNTHESIS AND CHARACTERISATION OF JATROPHA OIL-BASED WATERBORNE POLYURETHANE DISPERSIONS
SARIAH BINTI SAALAH
FK 2016 54
© COPYRIG
HT UPMSYNTHESIS AND CHARACTERISATION OF JATROPHA OIL-BASED
WATERBORNE POLYURETHANE DISPERSIONS
By
SARIAH BINTI SAALAH
Thesis Submitted to the School of Graduate Studies, Universiti Putra Malaysia, in
Fulfilment of the Requirements for the Degree of Doctor of Philosophy
March 2016
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COPYRIGHT
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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
SYNTHESIS AND CHARACTERISATION OF JATROPHA OIL-BASED
WATER-BORNE POLYURETHANE DISPERSIONS
By
SARIAH BINTI SAALAH
March 2016
Chairman : Professor Luqman Chuah Abdullah, PhD
Faculty : Engineering
The transition from solvent-borne to waterborne polyurethane (PU) coatings is driven by
the stringent regulations to reduce emissions of volatile organic compounds (VOCs)
from the products, enhanced by the increasing awareness of the consumers of safety and
health issues. On the other hand, a low cost, abundant, and renewable vegetable oil
source is now receiving increasing attention for polyurethane production. Previous
studies reported the possibility of the production of PU coatings, adhesives and
elastomers from non-edible jatropha oil. However, as far as is known, no study has
reported on waterborne PU synthesis from jatropha oil. In this research, jatropha oil is
modified to polyol to be used as a starting material for the production of a waterborne
PU dispersion. A series of jatropha oil-based polyols (JOLs) were synthesised from
jatropha oil by a two-step process, namely epoxidation and oxirane ring opening. The
effect of epoxidation conditions on the properties of the JOLs was investigated. The JOLs
are liquid under room conditions with a hydroxyl number in a range of 138 to 217 mg
KOH/g.
The jatropha oil-based waterborne polyurethane (JPU) dispersions were produced by
polymerising the JOLs with isophrene diisocyanate (IPDI) and dimethylol propionic acid
(DMPA). The colloidal stability of the resulting JPU dispersions were studied by particle
size analysis and rheology measurements. Inclusion of up to 5.4 wt.% of DMPA as an
internal emulsifier produced a wide range of particle sizes from 84 nm to 825 nm.
However, further increasing the DMPA content up to 6.8 wt.% resulted in smaller
particles but a multimodal particle size distribution was obtained for the dispersion
synthesised from low OH number polyol. The dispersions have a solid content of 22.9 to
26.9 wt.% with a relatively low viscosity in the range 5.6-53.1 mPa.s. The JPU
dispersions exhibited the typical flow behaviour of the commercial polyurethane
dispersions, ranging from almost Newtonian to a shear thinning fluid, and the
experimental data correlated well with the Cross model. The samples were stable after
18 months of storage under room conditions.
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A films with up to 62 wt.% bio-based content were successfully produced after
evaporation of water from the JPU dispersion. The chemical, physical, mechanical and
thermal properties of the films were characterised. The experimental data revealed that
the OH number of the JOLs, DMPA content and the hard segments were the key
parameters which control the structure and the properties of the JPU films. The JPU film
derived high OH number polyol and high hard segment content exhibited the highest
crosslinking density. This contributed to higher hardness, better mechanical properties,
and hydrophobic surface character. The films show an elastomeric polymer behaviour
and good thermal stability.
The JPU dispersions were applied on a wood surface and the performance of the coatings
were evaluated. The JPU films have excellent adhesion to the substrate, excellent optical
properties as well as chemical and abrasion resistance. The PU dispersions synthesised
in this work possess good properties with a promising application as a standalone coating
or binder for wood and decorative coatings.
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Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia
sebagai memenuhi keperluan untuk ijazah Doktor Falsafah
SINTESIS DAN PENCIRIAN DISPERSI POLIURETANA BERBASIS AIR
YANG BERASASKAN MINYAK JATROPHA
Oleh
SARIAH BINTI SAALAH
Mac 2016
Pengerusi : Profesor Luqman Chuah Abdullah, PhD Fakulti : Kejuruteraan
Peralihan daripada poliuretana (PU) berbasis pelarut kepada dispersi PU berbasis air
adalah didorong oleh peraturan ketat untuk mengurangkan pembebasan sebatian organik
meruap (VOC) daripada produk, ditambah pula dengan peningkatan kesedaran pengguna
mengenai isu-isu keselamatan dan kesihatan. Minyak sayuran yang merupakan sumber
boleh diperbaharui dan boleh diperolehi dengan harga yang murah kini mendapat
perhatian utama dalam penghasilan PU. Kajian lepas mendapati minyak jatropha boleh
digunakan untuk membuat bahan penyalut, perekat dan elastomer. Walaubagaimanapun,
tiada kajian dilaporkan mengenai pembuatan dispersi PU berbasis air daripada minyak
jatropha. Dalam kajian ini, minyak jatropha diubah suai kepada poliol untuk digunakan
sebagai bahan untuk pembuatan PU berbasis air. Satu siri poliol telah dihasilkan melalui
dua langkah, iaitu pengepoksidaan dan pembukaan cincin oksiran. Kajian dilakukan
untuk mengenalpasti kesan kondisi epoksidasi terhadap sifat poliol yang dihasilkan.
Hasil ujikaji mendapati semua JOL bersifat cecair pada keadaan bilik dengan nilai
nombor hidroksil antara 138 hingga 217 mg KOH/g.
Dispersi PU berbasis air yang berasaskan minyak jatropha (JPU) telah berjaya dihasilkan
melalui tindak balas pempolimeran antara JOL dengan isoprena diisosianat (IPDI), dan
dimetilol asid propionik (DMPA). Kestabilan koloid JPU dalam air dikaji melalui
analisis saiz partikel dan juga reologi. Penambahan sehingga 5.4% DMPA sebagai
pengemulsi dalaman menghasilkan pelbagai saiz partikel daripada 84 nm hingga 825 nm.
Apabila kandungan DMPA ditingkatkan sehingga 6.8 %, partikel yang lebih kecil
terhasil tetapi beberapa mod taburan saiz partikel telah diperolehi bagi JPU yang
disintesis daripada poliol dengan nombor OH yang rendah. Semua JPU ini disediakan
dengan kandungan berat pepejal 22.9-26.9 %, dan kelikatan yang rendah dalam julat 5.6-
53.1 mPa.s. JPU ini mempamerkan kelakuan dispersi poliuretana komersial, iaitu sama
ada hampir Newtonian atau shear-thinning, dan data eksperimen ini boleh diwakili oleh
model Cross. Sampel JPU didapati stabil di bawah 18 bulan penyimpanan pada keadaan
bilik.
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Filem yang mengandungi sehingga 62% berat kandungan berasaskan bio telah berjaya
dihasilkan selepas air disejatkan dari dispersi JPU. Ini menunjukkan kebolehan
pembentukan filem yang baik. Sifat-sifat kimia, fizikal, mekanikal dan haba filem yang
terhasil telah ditentukan. Data eksperimen menunjukkan bahawa kandungan kumpulan
berfungsi OH pada JOL, DMPA dan segmen keras adalah parameter utama yang
mengawal struktur dan sifat-sifat filem JPU. Filem yang disintesis daripada poliol yang
memiliki nombor OH tertinggi dan juga tinggi kandungan segmen kerasnya
mempamerkan ketumpatan silang yang paling tinggi, seterusnya menyumbang kepada
kekerasan yang lebih tinggi, sifat mekanikal yang lebih baik, dan mempamerkan
permukaan hidrofobik. Semua filem JPU mempamerkan kelakuan polimer lentur
mempunyai kestabilan terma yang tinggi.
Dispersi JPU berbasis air telah digunakan sebagai bahan pelapis untuk kayu dan prestasi
lapisan tersebut dinilai. JPU juga merekat sempurna terhadap substrat kayu JPU juga
merekat sempurna terhadap substrat kayu. Selain itu, lapisan tersebut mempamerkan ciri-
ciri optik yang sangat baik, begitu juga dengan rintangan kimia dan rintangan lelasannya.
Keseluruhannya, dispersi JPU berbasis air yang telah disintesis dalam kajian ini
mempunyai ciri-ciri yang baik dan berpotensi digunakan sebagai bahan pelapis atau
pengikat untuk formulasi bahan pelapis kayu dan hiasan.
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ACKNOWLEDGEMENTS
First and foremost, I thank to Allah s.w.t., the Almighty, for granting me countless
blessings, guidance and knowledge to complete this work. I would like to express my
sincerest gratitude and appreciation to my supervisor, Professor Dr. Luqman Chuah
Abdullah, who has supported me with his continuous trust, motivation and guidance
throughout this study. Without his constant encouragement this thesis would not have
been completed or written. I am also in debt to my excellent supervisory committee,
Professor Dr. Mahiran Basri, Dr. Min Min Aung, Dr. Mekzah Salleh and Dr. Dayang
Radiah Awang Biak for their extensive guidance, comments and suggestions which were
very precious for this research work.
My sincere appreciation also goes to staffs in the Radiation Processing Technology
Divison of Malaysia Nuclear Agency, Dr. Nik Ghazali, Ms Rida, Mr Rosli, Mr Hasnul,
Mr Zahid and Mr Wan for their full-cooperation during my study. Many thanks also to
Mr. Raman at Faculty of Engineering Lab for his assistance on rheometer instrument.
Special thanks to my graduate fellows, Emiliana Rose, Rabiatul Adawiyah, Suhaini,Siti
Hasnah, Saba Rashidi and Syeed Saifulazry for their company, support and
encouragement which has made my graduate studies an exciting and fulfilling journey.
I must acknowledge the Ministry of Higher Education (MOHE), Malaysia and
Universiti Malaysia Sabah (UMS) for giving me the financial support and opportunity to
pursue my PhD study in Universiti Putra Malaysia. I would also like to extend my
appreciation to Malaysia Nuclear Agency for the use of their chemicals and facilities.
Finally, I would like to extend my gratitude to my beloved husband, Dahlan, my dearest
sons, Luqman Hamiz and Lutfi Hanif, beloved parents, Saallah and Samira, dearest
brothers and sisters, Suryani, Herman, Herwan, Sharinee and Shahira. Their
unconditional love, encouragement, support and prayers were the driving force that
inspired me to succeed and build my strength and confidence to overcome the many
seemingly insurmountable obstacles in life. Their principles and guidance showed the
way.
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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:
Luqman Chuah Abdullah, PhD
Professor
Faculty of Engineering
Universiti Putra Malaysia
(Chairman)
Dayang Radiah Awang Biak, PhD
Senior Lecturer
Faculty of Engineering
Universiti Putra Malaysia
(Member)
Mahiran Basri, PhD
Professor
Faculty of Science
Universiti Putra Malaysia
(Member)
Min Min Aung, PhD
Senior Lecturer
Faculty of Science
Universiti Putra Malaysia
(Member)
Mek Zah Salleh, PhD
Senior Research Officer
Radiation Processing Technology Division
Malaysia Nuclear Agency
(Member)
BUJANG KIM HUAT, PhD
Professor and Dean
School of Graduate Studies
Universiti Putra Malaysia
Date:
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Sariah binti Saalah (GS34237)
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: ______________________
Name and Matric No.: ____________________________________________
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TABLE OF CONTENTS
Page
ABSTRACT i
ABSTRAK iii
ACKNOWLEDGEMENTS v
APPROVAL vi
DECLARATION viii
LIST OF TABLES xiv
LIST OF FIGURES xvi
LIST OF ABBREVIATIONS xx
CHAPTER
1 INTRODUCTION 1
1.1 Background of the study 1
1.2 Problem statement 3
1.3 Objectives of the study 4
1.4 Scope of the study 4
1.5 General overview of the thesis 5
2 LITERATURE REVIEW 6
2.1 World production, consumption and exports of vegetable oil 6
2.2 Jatropha curcas 7
2.2.1 Introduction to Jatropha curcas 7
2.2.2 Status of Jatropha curcas plantations in Malaysia 9
2.2.3 Application of Jatropha curcas 9
2.3 Vegetable oil as platform for polymer synthesis 10
2.3.1 Physico-chemical properties of vegetable oil 11
2.3.2 Vegetable oil-based polymeric materials 14
2.3.3 Previous research on jatropha oil-based polymer 17
2.4 Vegetable oil based-polyol for polyurethane 19
2.4.1 Introduction 19
2.4.2 Some important characteristics of oligomeric polyols 20
2.4.3 Vegetable oil-based polyol synthesis 21
2.4.4 Review of the properties of vegetable oil-based polyol 30
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2.5 Global polyurethane production and applications 33
2.6 Chemistry of polyurethane 34
2.7 Waterborne polyurethane dispersion 36
2.7.1 Introduction 36
2.7.2 Comparison of solvent-borne PU and waterborne PU
dispersions
37
2.7.3 Ingredients of waterborne polyurethane dispersion 38
2.7.4 Preparation of waterborne polyurethane dispersion 40
2.7.5 Colloidal stability of waterborne polyurethane dispersion 42
2.7.6 Film formation 43
2.8 Review of vegetable oil based waterborne polyurethane dispersion 44
2.8.1 Review of wet properties of PU dispersion 46
2.8.2 Review of mechanical properties of waterborne PU film
and coating
48
2.9 Phase separation of hard and soft segment in polyurethane 51
2.10 Crosslinking in vegetable oil-based polyurethane 51
2.11 Summary 53
3 METHODOLOGY 54
3.1 Description of methodology 54
3.2 Materials
3.3 Preparation of jatropha oil-based polyol 57
3.3.1 Epoxidation 57
3.3.2 Oxirane ring opening 59
3.4 Chemical analysis and characterisation of epoxidised jatropha oil
and jatropha oil-based polyol
60
3.4.1 Iodine value (IV) 60
3.4.2 Oxirane oxygen content and relative conversion to oxirane 60
3.4.3 Hydroxyl number and equivalent weight 61
3.4.4 Acid number 62
3.4.5 FTIR analysis 62
3.4.6 Rheological properties 62
3.4.7 Molecular weight determination 63
3.5 Synthesis of jatropha oil-based waterborne polyurethane (JPU)
dispersions
63
3.6 Characterisation of the jatropha oil-based waterborne (JPU)
dispersions
66
3.6.1 Particle size analysis 66
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3.6.2 Acid number, pH, and solid content measurements 66
3.6.3 Rheology analysis 66
3.6.4 Viscosity determination 66
3.7 Preparation of jatropha oil-based waterborne (JPU) films 66
3.8 Characterisation of jatropha oil-based waterborne (JPU) films 67
3.8.1 Fourier Transform Infrared Spectroscopy (FTIR) analysis 67
3.8.2 Crosslinking density measurement 67
3.8.3 Pendulum hardness test 68
3.8.4 Tensile properties measurement 68
3.8.5 Differential Scanning Calorimetry (DSC) analysis 69
3.8.6 Dynamic mechanical analysis (DMA) 69
3.8.7 Thermogravimetric analysis (TGA) 69
3.8.8 Water contact angle measurement 69
3.8.9 Water uptake determination 69
3.9 Evaluation of coating performance of the jatropha oil-based
waterborne (JPU) dispersions
70
3.9.1 Gloss measurement 70
3.9.2 Optical transmittance determination 70
3.9.3 Cross-cut adhesion test 70
3.9.4 Scanning Electron Microscopy ( SEM) analysis 70
3.9.5 Abrasion resistance test 72
3.9.6 Chemical resistance test 72
4 RESULTS AND DISCUSSION 73
4.1 Production of jatropha oil-based polyol by epoxidation and oxirane
ring opening
73
4.1.1 Structure analysis of jatropha oil, epoxidised jatropha oil
and jatropha oil-based polyol by FTIR
75
4.1.2 Effect of molar ratio, temperature and reaction time on the
oxirane oxygen content
77
4.1.3 Effect of oxirane oxygen content on hydroxyl value of
epoxidised jatropha oil (EJO)
78
4.1.4 Molecular weight and rheology of epoxidised jatropha oil
(EJO)
80
4.1.5 Molecular weight, physico-chemical and rheological
properties of jatropha oil-based polyol (JOL)
83
4.1.6 Section conclusion 87
4.2 Synthesis, stability and rheology of jatropha oil-based waterborne
polyurethane (JPU) dispersion
88
4.2.1 Monitoring polyurethane synthesis by FTIR 90
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4.2.2 Particle size analysis 92
4.2.3 Physico-chemical charecteristics 96
4.2.4 Rheological properties 99
4.2.5 Drying characteristic 110
4.2.6 Stability upon storage 112
4.2.7 Section conclusion 114
4.3 Jatropha oil-based waterborne polyurethane (JPU) film 115
4.3.1 Structure analysis by FTIR 115
4.3.2 Crosslinking density 118
4.3.3 Pendulum hardness 120
4.3.4 Tensile properties 123
4.3.5 Thermal properties by DSC 126
4.3.6 Thermo-mechanical properties by DMA 128
4.3.7 Thermal degradation profile by TGA 133
4.3.8 Water contact angle analysis 137
4.3.9 Water uptake 140
4.3.10 Section conclusion 143
4.4 Coating performance of jatropha oil based waterborne polyurethane
(JPU)
144
4.4.1 Aesthetic properties 146
4.4.2 Adhesion properties 147
4.4.3 Abrasion resistance 148
4.4.4 Chemical resistance 149
4.4.5 Section conclusion 149
5 CONCLUSIONS AND RECOMMENDATIONS 150
5.1 Conclusions 150
5.2 Recommendations 150
REFERENCES 151
APPENDIX 161
BIODATA OF STUDENT 162
LIST OF PUBLICATIONS 163
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LIST OF TABLES
Table Page
1.1 Specification of commercial PU dispersion 5
2.1 World production and exports of major oil and fats 6
2.2 Utilisation of Jatropha curcas in various form 10
2.3 List of fatty acids compositions in some vegetable oils 12
2.4 Formulas and structures of the most important fatty acids 13
2.5 Previous research on jatropha oil-based polymer 18
2.6 Comparison of commonly employed polyol production method 29
2.7 Properties of vegetable oil-based polyols produced by various
methods
31
2.8 Properties of commercial polyols from various modifications of
vegetable oils
32
2.9 Solvent-borne vs waterborne PU dispersion 38
2.10 Previous studies on waterborne PU xivynthesized from vegetable
oil
45
2.11 Wet characteristics of waterborne PU dispersion derived from
various types of soft segment
47
2.12 Mechanical properties of vegetable oil-based and petro-based
waterborne PU dispersion
49
3.1 Reaction parameters for epoxidation step and acid value of
epoxidised jatropha oil (EJO)
58
3.2 Raw materials used for synthesis of jatropha oil-based
polyurethanes (JPU) dispersion
63
3.3 The formulation of jatropha oil-based polyurethanes (JPU)
dispersion
65
3.4 Classification of adhesion test results 71
3.5 Code of assessment against ethanol of coatings on substrate 72
4.1 Yield of polyol production 80
4.2 Molecular weight of epoxidised jatropha oil 80
4.3 Molecular weight of JOL 83
4.4 Physico-chemical properties of the JOL 84
4.5 Viscosity at 45 °C and activation energy of viscous flow (Ea) for
the jatropha oil-based polyols
86
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4.6 Some properties of the JPU dispersions with different OH numbers
(Group A)
97
4.7 Some physical properties of JPU dispersion with 45 wt.% hard
segment (Group B)
97
4.8 Cross equation parameters for the JPU dispersions (Group A) 101
4.9 Cross equation parameters for the JPU 161i dispersions with
various solid content
102
4.10 Characteristic IR band of JPU film 116
4.11 Swelling and sol fraction of JPU films in toluene 118
4.12 Crosslinking density, molecular weight between crosslinks, and
solubility characteristics of the JPU films in toluene
120
4.13 Tensile properties of JPU films 124
4.14 The glass transition temperature (Tg) of JPU films 127
4.15 Dynamic mechanical properties of JPU films 130
4.16 The thermal properties of JPU films from polyol with different
hydroxyl values
135
4.17 Water contact angle of the JPU films 139
4.18 Water uptake of the JPU films 142
4.19 Properties of JPU dispersion in comparison with other vegetable
oil based waterborne PU dispersions
145
4.20 Gloss value and adhesion of JPU coating on wood substrate 146
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LIST OF FIGURES
Figure Page
2.1 World major consumers of oil and fats 7
2.2 Production of oil from the seed of jatropha curcas fruit 8
2.3 Life cycle of materials based on vegetable oil 11
2.4 Triglyceride production by condensation reaction 11
2.5 Jatropha oil triglyceride structure 14
2.6 Functional groups in triglyceride structure of vegetable oil 14
2.7 Possible transformation of modified vegetable oil to polymeric
coating materials (a) alkyd, (b) polyetheramide, (c) polyurethane
16
2.8 The general formula of oligomeric polyol 19
2.9 Various routes for the modification of vegetable oil to polyols 22
2.10 Transesterification of castor oil 23
2.11 Ozonolysis of vegetable oil 24
2.12 Representative of canola oil-based polyol structures 24
2.13 Modification of vegetable oil by hydroformylation followed by
hydrogenation
25
2.14 Thiol–ene reaction of mercaptanised soybean oil with glycerol-1-
allyl ether
26
2.15 Epoxidation reaction mechanism 26
2.16 Possible side reaction of epoxy groups 27
2.17 Schematic representation of dimer formation 27
2.18 Oxirane ring opening of epoxidised vegetable oil by various
chemicals
28
2.19 Global PU production in 2012 33
2.20 Main application of PU 34
2.21 Typical reactions of isocyanates involved in the synthesis of
polyurethane
35
2.22 Common diisocyanates used in the synthesis of polyurethane 36
2.23 Schematic diagrams of micelles formed by (a) cationic and (b)
anionic polyurethane ionomers in water
37
2.24 Synthesis of soybean oil-based waterborne PU dispersion 41
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2.25 Zeta potential influence whether the particles tend to repel or
attract each other
43
2.26 Typical film formation behaviour during drying of latex 44
3.1 Overview of experimental works 55
3.2 Detailed research flow and sample characterisations 56
3.3 Experimental setup for epoxidation step 58
3.4 Experimental setup for oxirane ring opening step 59
3.5 Experimental setup for polyurethane synthesis 64
3.6 Preparation of waterborne polyurethane dispersion 65
3.7 Wet JPU dispersions casted in teflon mold: a) JPU 161, b) JPU
188, c) JPU 217, the resulting dry JPU film and JPU free film.
67
3.8 Dimension of tension test specimen 68
4.1 Proposed schematic of jatropha oil-based polyol production via
epoxidation and oxirane ring opening method
74
4.2 Appearance of jatropha oil-based polyol (b), compared with the
starting jatropha oil (a)
74
4.3 FTIR spectra of jatropha oil (JO), epoxidised jatropha oil (EJO)
and jatropha oil-based polyol (JOL)
76
4.4 Effect of molar ratio and reaction temperature on OOC of
epoxidised jatropha oil
77
4.5 Effect of molar ratio and reaction temperature on relative
conversion to oxirane of epoxidised jatropha oil
78
4.6 Effect of reaction time on OOC of epoxidised jatropha oil 79
4.7 Effect of %OOC of EJO on the OH number of JOL 79
4.8 The molecular weight distribution of EJO 4.5h 81
4.9 Viscosity curve of jatropha oil (JO) and epoxidised jatropha oil
(EJO) at 25 °C.
82
4.10 Viscosity of jatropha oil (JO) and epoxidised jatropha oil (EJO) at
various temperatures.
82
4.11 Viscosity curves of jatropha oil-based polyol with different OH
numbers at 25 °C
84
4.12 Viscosity of jatropha oil-based polyol at various temperatures at a
shear rate of 250 s-1
85
4.13 Viscosity–temperature relationship for jatropha oil-based polyols
(JOLs).
86
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4.14 Proposed reaction scheme for synthesis of water-borne
polyurethane dispersions
89
4.15 FTIR spectra of the polyol (JOL) and polyurethane (JPU)
prepolymer
90
4.16 FTIR spectra of a) isocyanate group in polyurethane, b) hydroxyl
and urethane group in polyol and polyurethane respectively, c)
carbonyl and urethane group in polyurethane
91
4.17 Particle size, zeta potential and particle size distribution of the JPU
dispersion from polyol with various OH numbers
93
4.18 Effect of soft segment content (a) and DMPA content (b) on the
particle size of the JPU dispersion
94
4.19 Particle size distribution of JPU dispersions with 45 wt.% hard
segment content
96
4.20 Visual appearance of JPU 217, JPU 161 and JPU 161 98
4.21 Visual appearance of JPU dispersions 98
4.22 Production of a transparent JPU film by water evaporation from a
JPU dispersion
98
4.23 Viscosity of JPU dispersions as a function of shear rate at 25 °C.
The lines are computed from Equation 4.2 using the nonlinear
regression technique
100
4.24 Viscosity of JPU 161i with various solid content as a function of
shear rate at 25 °C. The lines are computed from Equation 4.2
using the nonlinear regression technique.
102
4.25 Master curve of JPU 161i created by normalising the sample
viscosity by the zero shear viscosity, ηo and the shear rate by the
critical shear rate, γc . A summary of the values of ηo, γc, and β are
given in Table 4.9.
103
4.26 Strain sweep analysis of JPU 217 at various temperatures (ω =
6.283 rad/s)
104
4.27 (a) Frequency dependence of dynamic storage modulus, G', loss
modulus, G", and complex viscosity, η*, of JPU 217 (b) Frequency
dependence of dynamic storage modulus, G', loss modulus, G",
and complex viscosity, η*, of JPU 161i (25 °C, 2 % strain)
106
4.28 (a) Temperature dependence of dynamic storage modulus, G', loss
modulus, G", and complex viscosity, η*, of JPU 217 (b)
Temperature dependence of dynamic storage modulus, G', loss
modulus, G", and complex viscosity, η*, of JPU 161i (ω=6.283
rad/s, 2% strain)
108
4.29 Schematic of aggregation and gel formation of colloidal dispersion 109
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4.30 Viscosity as a function of shear rate, and complex viscosity as a
function of angular frequency for JPU 161 and JPU 217
110
4.31 Effect of wet thickness on the drying time of JPU 217 111
4.32 Effect of JPU variations on drying time 111
4.33 Effect of storage time on the viscosity of JPU dispersions 112
4.34 Effect of storage time on the particle size distribution of JPU
dispersion
113
4.35 FTIR spectra of JPU 217 film 116
4.36 FTIR spectra of amide (a) and carbonyl (b) regions of JPU films 117
4.37 Position of reactive site at the fatty acid chain of polyol: (a) oleic
acid, b) linoleic acid, c) stearic acid
119
4.38 Pendulum hardness of JPU films with different hard segment
content (Group A)
121
4.39 Pendulum hardness of JPU films with 45 wt% hard segment
content (Group B)
122
4.40 Schematic illustration of the microstructure of JPU 122
4.41 Stress-strain curve of JPU films (Group A) 124
4.42 Stress-strain curve of JPU films with hard segment of 45 wt.%
(Group B)
125
4.43 DSC thermograms of JPU films (Group A) 126
4.44 DSC thermograms of JPU films with a hard segment of 45 wt.%
(Group B)
128
4.45 Storage modulus a) and, tan delta b), as a function of temperature
for JPU films produced from various OH number polyol (Group
A)
129
4.46 Storage modulus a), and tan delta b), curves as a function of
temperature for JPU films with 45 wt.% hard segment (Group B)
132
4.47 TG and derivative TG (DTG) curves of JPU films (Group A) 134
4.48 TG and derivative TG (DTG) curves of JPU films (Group B) 136
4.49 Water contact angle as a function of time for JPU films with
various hard segment content (Group A)
138
4.50 Image of a drop of water on the surface of JPU 217 film 138
4.51 Water contact angle as a function of time for JPU films with 45
wt.% hard segment content (Group B)
140
4.52 Water swelling of JPU films with various hard segment content
(Group A)
141
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4.53 Water uptake of JPU films with hard segment content of 45 wt.%
(Group B)
143
4.54 Wood sample coated with JPU dispersion compared to an
uncoated wood sample
144
4.55 SEM image of the cross section of a wood sample coated with JPU
dispersion (200X magnification)
147
4.56 Weight loss of JPU films as a function of abrasion cycles 148
4.57 Variation of chemical resistance against ethanol of JPU coating 149
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LIST OF ABBREVIATIONS
ASTM American Standard for Testing Material
ATR Attenuated total reflectance
CAGR Compound annual growth rate
DMA Dynamic Mechanical Analysis
DMPA Dimethylol propionic acid
DSC Differential Scanning Calorimeter
DTG Derivative of thermogravimetric (TG) curve
E Young’s modulus
E' Storage modulus (tension mode)
E" Loss modulus (tension mode)
Ea Activation energy
EDA Ethylene diamine
EJO Epoxidised jatropha oil
EW Equivalent weight
FTIR Fourier Transform Infrared
G' Storage modulus (shear mode)
G" Loss modulus (shear mode)
GPC Gel permeation chromatography
HDA 1-6 Hexanediamine
HEMA 2-Hydroxyethyl methacrylate
H12MDI 4-4 dicyclohexylmethane diisocyanate
IPDI Isophrene (or isophorone) diisocyanate
IV Iodine value
JO Jatropha oil
JOL Jatropha oil-based polyol
JPU Jatropha oil-based waterborne polyurethane
MDI Diphenylmethane diisocyanate
MFFT Minimum film forming temperature
OOC Oxirane oxygen content (%)
OOCth Theoretical oxirane oxygen content (%)
PU Polyurethane
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SEM Scanning Electron Microscope
TEA Triethylamine
TDI Toluene diisocyanate
TGA Thermogravimetric Analysis
ZP Zeta potential (mV)
d50 Average particle size (nm)
gram/eq Gram per equivalent
Mc Molecular weight between crosslink
Mn Number average molecular weight (Dalton)
Mw Weight average molecular weight (Dalton)
n Flow index behavior
OH Hydroxyl
R Universal gas constant
Tan δ Damping, ratio of E"/E'
Tg Glass transition temperature (°C)
𝜎 Tensile strength (MPa)
𝐵 Titration of blank (mL)
휀 Elongation at break (5)
η Viscosity (mPas)
η* Complex viscosity (mPas)
𝑁 Normality
𝑊 Weight (g)
𝑆 Titration of the sample (mL)
ƒ Functionality
𝜔 Angular frequency (s-1)
𝜌2 Density of dry polymer
γ Shear rate (s-1)
δ Solubility parameter
v1 Molar volume of solvent
υe Crosslinking density
∅2 Volume fraction of polymer in the swollen network
𝜒12 Polymer–solvent interaction parameter
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CHAPTER 1
INTRODUCTION
1.1 Background of the study
Polyurethane (PU) is a versatile polymer which has been employed in a wide range of
applications, such as coatings, adhesives, sealants, foams, elastomers, and others. With
a proper selection of reactant, PU ranges from high performance elastomers to tough and
rigid plastics can be easily fabricated (Lu & Larock, 2008). PU based coatings have an
established place in the coatings industry due to the high level of quality such as
outstanding chemical and corrosion resistance, excellent abrasion resistance, low
temperature flexibility, high toughness, and a wide range of mechanical strength (Kong,
et al., 2013; Melchiors et al., 2000). Basically, polyurethane backbone structures consist
of a soft segment from polyol, and a hard segment from isocyanate. The hard segments
govern the hardness, strength and toughness of the PU films, while the soft segments
determine the flexibility and glass transition temperature. The versatile mechanical
properties of PU arise from phase separation of the thermodynamically incompatible
hard and soft segments, which arrange themselves in microdomains as a result of a
hydrogen bonding bridge between the urethane groups (Kanda et al., 2008). The
hydrogen bridge bond forms a stable physical network, ensuring the outstanding
mechanical properties of the PU film, while the urethane groups helps to protect the
polymer chain against solvents, acids, bases and other chemicals (Melchiors et al., 2000).
Traditional PU coatings have been diluted with an organic solvent that helps to carry the
coatings from the applicator to the substrate. Organic solvents often contain volatile
organic compounds (VOCs). The emission of VOCs during the formulation of coatings,
inks, and paints has caused a wide variety of air quality problems (Nanda & Wicks,
2006). With enforcement of stringent regulations aimed at preventing pollution, such as
the Clean Air Act, the application of solvent-borne coatings has been phased out and
replaced with coatings free of VOCs such as waterborne coatings and ultraviolet (UV)
curable coatings (100 % solid) (Athawale & Kulkarni, 2010; DeVito, 1999; Ristić et al.,
2012). In Europe, waterborne technology has been accepted as it has become the largest
volume of coatings particularly in terms of decorative coatings (Scrinzi et al., 2011).
These products fulfil many of the requirements related to conventional solvent-borne
coatings, e.g., low viscosity at a high molecular weight and good applicability (Cakić et
al., 2013). The transition from solvent-borne to waterborne PU may lower the
manufacturing costs associated with solvent cost, and reduce the health and fire risks
(Garrison et al., 2014). It has been forecast that the global PU dispersion market will
grow at a CAGR of 7.5 % in the years 2012 to 2018, with the market value estimated to
be worth US $ 1.18 billion by 2018 (Transparency Market Research, 2015b).
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Waterborne polyurethane (PU) dispersion is a typical colloid system consisting of PU
particles stabilised in a continuous water phase. In preparing a waterborne PU dispersion,
ionomers which contain hydrophilic groups are incorporated into the side chain or the
backbone of the polymer to enable dispersibility of the water-insoluble polyurethane.
Anionic ionomers such as dimethylol propionic acid (DMPA) act as an emulsifier to
provide dispersion stability for longer storage of the waterborne PU dispersion.
Currently, most waterborne PU dispersions are derived from a petroleum based polyol
which is non-renewable. As fossil resources become depleted, coupled with awareness
of environmental issues related to non-biodegradable products, utilisation of more
sustainable and environmentally friendly raw materials for fabrication of bio-based
polymers is gaining increasing attention. Recently, the successful synthesis of
waterborne PU dispersions from vegetable oil based polyol derived from soybean oil,
castor oil, rapeseed oil and linseed oil has been reported (Chang & Lu, 2013; Lu &
Larock, 2008; Ni et al., 2010). However, to the best of the knowledge of the authors, no
research has been reported on the production of waterborne PU dispersions from non-
edible jatropha oil. In Malaysia, jatropha has become one of the most important crops
after palm oil and rubber, mainly planted for biodiesel production. BATC Development
Berhad has been actively engaged in jatropha plantation and the bio-fuel industry since
2007. Up to 2011, about 600,000 acres of planted area, 3.3 million acres in landbanks
and more than 300 nurseries and collection centres were reported in Malaysia (Bionas,
2011).
Jatropha oil (JO) which is extracted from the seeds of the jatropha fruit is a promising
candidate for chemical purposes as it contains 78.9 % unsaturated fatty acids, mainly of
oleic acid (43.1 %) and linoleic acid (34.4 %) (Sarin et al., 2007). This high degree of
unsaturation provides a broad alternative for chemical modification to produce polymers
with the desired properties. Furthermore, the utilisation of a non-edible jatropha oil will
reduce the dependency on edible oils for chemical purposes (Rios et al., 2011). Previous
research has revealed the potential usage of jatropha oil for production of various
polymers with promising properties such as alkyd resin, PU coatings, PU adhesive and
PU elastomer (Aung et al., 2014; Boruah et al., 2012; Harjono et al., 2012; Hazmi et al.,
2013). In this research, an attempt is made to extend the potential of jatropha oil as a
starting material for the production of a waterborne PU dispersion.
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1.2 Problem statement
Malaysia is among the largest of the world’s producers of palm oil. In the coating
industry, successful utilisation of such oil has been reported to produce alkyd resin,
epoxy palm oil, oleic acid acrylate resin and PU acrylate for wood coatings and overprint
varnish applications (Rozman et al., 2013). Due to the low unsaturation in palm oil
composition, production of a coating polymer from palm oil is more towards ultra-violet
(UV) curable acrylate resin from palm oil derivatives such as oleic acid and palm oil
monoglyceride (Rozman et al., 2013; Salleh et al., 2010; Wan Rosli et al., 2003).
Realising the importance of reducing the dependency on edible oil for polymer
fabrication, the non-edible jatropha oil is a new alternative. With almost 80 %
unsaturated fatty acids, the double bond in the oil triglyceride structure could be directly
functionalised to hydroxyl in polyol preparation.
Generally, vegetable oil with a high degree of C=C unsaturation will result in a high OH
number polyol for crosslinking with isocyanate to produce polyurethane with good
mechanical properties (Meier et al., 2007). The fatty acid composition of the starting
vegetable oil and the polyol production method determine the properties of the final
polyol such as OH number, molecular weight and rheology. As the polyol and isocyanate
are the main ingredients in PU, the higher amount of polyol loading will increase the bio-
based content. Typically, up to 60 wt.% bio-based content has been reported (Lu &
Larock, 2008). Therefore, depending on the specific application, the properties of the PU
could be tailored by varying the OH number of the polyol. The OH numbers will
determine the appropriate amount of hard segment required for polymerisation. If a high
bio-based PU is targeted, a low OH functionality polyol is selected, but the final film
properties should be considered. The non-functional groups in the polyol may result in a
tacky product which is undesirable for coating applications, but may be a characteristic
of a pressure sensitive adhesive (Wool, 2005). On the other hand, the high functionality
of some vegetable oil polyols may gel during polymerisation due to the higher
crosslinking and therefore present potential difficulties in dispersing the PU prepolymers
into water (Lu & Larock, 2008).
It is worth mentioning that the properties of the polyol also depend on the production
method. As far as an industrially important two-step method, i.e. epoxidation followed
by oxirane ring opening route, is concerned, various parameters should be controlled at
each consecutive stage (Goud et al,, 2010; Saurabh et al., 2011). Therefore, it is very
important to conduct a systematic study of the effect of epoxidation parameters on the
properties of jatropha oil-based polyol especially the OH numbers, as these will affect
the properties of the waterborne polyurethane dispersions in the wet colloidal state as
well as in the dry film state.
In general, the characteristics of the colloidal dispersions do not directly affect the
mechanical properties of the resulting dry films. However, information on the colloidal
stability and rheology of the dispersion is important with respect to storage and
application. For example a low viscosity and molecular weight independent of the
dispersed polymer is necessary for spray applications, but low zero shear rate viscosity
is subject to sedimentation of the PU particles upon storage (Duffy, 2015; Kastner, 2001).
A few factors have been reported to affect the stability of colloidal PU dispersions such
as the degree of neutralisation and the stirring procedure. However, these are less
important when compared to the ionic emulsifier content (Philipp & Eschig, 2012). The
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ionic groups in the DMPA are reported to improve the mechanical properties, but tend
to make the dispersion film more sensitive to water and chemicals (Bullermann et al.,
2013). Therefore, the amount of DMPA should be controlled to be as low as possible yet
sufficient to stabilise the PU particles upon storage. In addition, a balanced composition
between soft segment (polyol) and the hard segment in the PU formulation is an
important criterion to determine the mechanical properties of the polymers (Ni et al.,
2010).
In this study, jatropha oil based waterborne PU dispersions will be prepared and
characterised. The effect of polyol OH number, DMPA content and hard segment content
with the stability of the wet jatropha oil-based polyurethane (JPU) dispersion and the
physical, mechanical and thermal properties of the dry JPU films will be studied. On the
other hand, the performance of the JPU dispersion as wood coatings will be evaluated.
These properties will have an influence on the practical design of products as the PU
dispersion can be used as a standalone coating or as a binder in wood and decorative
coatings.
1.3 Objectives of the study
The main objective of this study is to investigate feasibility of producing jatropha oil-
based waterborne polyurethane dispersions for coating applications. To achieve this
objective, specific objectives have been identified:
a. To investigate the effect of epoxidation conditions (molar ratio, time,
temperature) on the properties of jatropha oil-based polyol.
b. To investigate the effect of hard segment, hydroxyl number, and ionic
emulsifier content on the colloidal stability and rheological properties of
jatropha oil-based waterborne polyurethane dispersions.
c. To relate the effect of hard segment, hydroxyl number and ionic emulsifier
content on the physical, mechanical and thermal properties of jatropha oil-based
waterborne polyurethane films.
d. To evaluate the coating performance of jatropha oil-based waterborne
polyurethane.
1.4 Scope of the study
The scope of the study can be expressed as follows.
a. Preparation of jatropha oil based polyol by epoxidation and oxirane ring
opening. Two series of epoxidised jatropha oil (EJO) to be obtained by varying
the molar ratio formic acid to oil double bond from 0.4 to 1.0, at different
temperatures, 50 °C and 60 °C. The third series to be produced at a fixed molar
ratio of 0.6, temperature of 60 °C but with different reaction times. Only the
third series will be selected for the oxirane ring opening step to produce jatropha
oil-based polyols (JOL). The chemical and rheological properties of the EJO
and JOL are to be investigated.
b. Preparation of a jatropha oil based waterborne polyurethane (JPU) dispersion
by the acetone method. Two group samples will be prepared: 1) a fixed molar
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ratio with varied hard segment (34-45 wt.%), and 2) a fixed hard segment at 45
wt.%.
c. The colloidal stability of the JPU dispersion is to be evaluated by particle size
analysis as well as rheological analysis.
d. The chemical, physical, mechanical and thermal properties of the JPU films are
to be investigated and correlated with the composition of the JPU. Four samples
will be selected for a coating application on wood substrate, and the
performance of the coatings evaluated.
In this study, a waterborne JPU dispersion with properties that are comparable to a
commercial PU dispersion is targeted. The specification of the commercial waterborne
petro-based PU dispersion is provided in Table 1.1.
Table 1.1. Specification of commercial PU dispersion (Adapted from Kamsons
Chemicals Pvt. Ltd. (n.d.))
Product name: Kamthane K-1432
Type Anionic, aliphatic
Appearance Milky white
Total solids (% w/w) 38
pH 7.0-8.5
Viscosity (mPa.s) 30-90 (at 30 °C)
Elongation at break (%) 550
Konig hardness (s) 40
1.5 General overview of the thesis
The thesis is organised in five chapters. The first chapter provides the background of the
research with an introduction to the waterborne polyurethane, followed by the problem
statement, as well as the objectives and the scope of the present research.
In the second chapter, literature related to the modification of vegetable oil to polyol as
well as the previous study on waterborne polyurethane is reviewed.
The third chapter focuses on the materials and methodology involved in the multistage
preparation and characterisation of waterborne polyurethane from jatropha oil.
Chapter four covers the results and discussion of all experimental works. To facilitate
the reading, the chapter is divided into four parts; 1) Production of jatropha oil-based
polyol by epoxidation and oxirane ring opening, 2) Synthesis, stability and rheology of
jatropha oil-based waterborne polyurethane dispersion, 3) Properties of jatropha oil-
based waterborne polyurethane films, and 4) Performance of the waterborne
polyurethane as wood coating.
Finally, the conclusions and recommendations are summarised in Chapter five.
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