ABSTRACT
Soybean oil is among the most abundant, biodegradable, renewable and sustainable vegetable oil in Nigeria that is rich in polyunsaturated fatty-acids, which earned a good candidate for epoxidaton. However, the epoxidized soybean oil (ESO) alone lacks good thermo-mechanical properties. Therefore, ESO is synthesized, thermally pre-cured and finally cured with polystyrene to obtain a blend of good thermo-mechanical properties. The soybean oil sample was subjected to FT-IR spectroscopy to determine the characteristic bands of functional groups, and then analyzed to determine the number of carbon-carbon double bond(s) present in 100g of the oil sample. The result indicated 149.8 as the iodine number. The resultant/determined number of carbon-carbon double bonds was interpreted in terms of molar equivalent and then stoichiometrically combined with peracetic acid (formed in-situ) to yield 9.77% oxirane-oxygen content of the soybean epoxy resin. The resin was subjected to Fourier Transform Infra-Red (FT-IR) spectroscopy within the frequency range of (400-4000) cm-1. The observable peaks showed a characteristic band of 843cm-1, 823cm-1 903cm-1 corresponding to internal, external and terminal oxirane-oxygen rings respectively, with disappearance at peak 3008 and 914 cm-1 at cis- and trans-, di-substituted olefins in soybean oil sample. The epoxidized soybean oil (ESO) was cured thermally to yield a gel coded as modified epoxidized soybean oil (MESO). The MESO was subjected to FT-IR, and the characteristic bands obtained indicated 3400cm-1and above. The MESO was blended with polystyrene in the ratio of 10/0, 9/1, 8/2, 7/3, 6/4, 5/5, 4/6 PS/MESO respectively. The mechanical properties of the blend were studied and the results indicated that 6/4 blend of PS/MESO gave highest values of tensile strength (4.3 x 105 Nm-2) and Young‘s modulus(14.9 x 105 Nm-2) and a lower value of elongation at break 29%. Viscometric study of the blends were carried out and the results affirmed that the blend at 6/4
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PS/MESO composition gave the additive value of R2 from both relative and reduced viscosity measurements respectively. The study showed that thermally cured resin of soybean oil is compatible with polystyrene and thus, at 6/4 PS/MESO composition, serves as reinforcement to polystyrene matrix.
TABLE OF CONTENTS
Title page i
Declaration ii
Certification iii
Acknowledgement iv
Abstract v
Table of contents vii
List of Figures xii
List of Table xiv
List of Plate xv
List of Appendices xv
Abbreviations xvi
viii
CHAPTER ONE
1.1 INTRODUCTION 1
1.2 Research Problem/Background of the Study 3
1.3 Justification of the Study 4
1.4 Scope (Limitations) of the Study 4
1.5 Aim and Objectives of the Study 4
CHAPTER TWO
LITERATURE REVIEW
2.0 Soybean Oil 5
2.1 Fatty acid distribution in soybean oil 5
2.2 List of Physicochemical properties of soybean oil 6
2.2.1 Iodine Value 6
2.2.2 Peroxide value 6
2.2.3 Acid value and Free Fatty acids 6
2.3 Double Bonds in vegetable oils 7
2.3.1 Mechanism of ―drying oil‖ (auto-oxidation of double bonds) 9
2.3.2 Processes of auto-oxidation of conjugated double bond 10
2.4 Epoxidation of soybean oil 12
2.4.1 Equation of peracid formation 12
2.4.2 Mechanism of epoxidation 13
2.5 Viscosity of polymer solution 19
2.5.1 Pressure flow 20
2.5.2 Capillary rheometry 20
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2.5.3 Capillary viscometer 21
2.5.4 Intrinsic viscosity measurement 21
2.6 Thermodynamic of polymer solution 23
2.6.1 Criteria for polymer solubility 26
2.6.2 Solubility parameter 26
2.7 Alloys and Blends 29
2.8 Mechanical properties of polymers 34
2.8.1 Mechanical tests 35
2.8.2 Stress- Strain experiments 36
2.8.3 Creep experiments 36
2.8.4 Stress relaxation experiments 37
2.8.5 Dynamic mechanical experiments 37
2.8.6 Impact experiments 39
2.8.7 Stress-strain behaviors of polymers 42
2.8.8 Deformation of solid polymers 43
2.9 Effects of structural and environmental factors on mechanical properties 46
2.9.1 Effect of molecular weight on mechanical properties 47
2.9.2 Effect of Cross-Linking On The Mechanical Properties 48
2.9.3 Effect of crystallinity on the mechanical properties 48
2.9.4 Effect of copolymerization 48
2.9.5 Effect of plasticizers 49
2.9.6 Effect of polarity 49
2.9.7 Steric factors 50
2.9.8 Effect of temperature 50
2.9.9 Effect of strain rate 51
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2.9.10 Effect of pressure 51
2.10 Processing techniques 52
2.10.1 Extrusion process 53
2.10.2 Molding process 59
2.10.3 Casting 73
CHAPTER THREE
MATERIALS AND METHODS
3.1 Equipment 76
3.2 Methods 78
3.2.1 Iodine Number Determination (Wij‘s Solution Method) 78
3.2.2 Epoxidation of Soybean Oil (Conventional Method) 79
3.2.3 FT-IR Characterization of Oil Samples 80
3.2.4 Determination of Oxirane-Oxygen of the ESO 80
3.2.5 Thermal Curing of Epoxidized Soybean Oil Sample (MESO Synthesis) 81
3.2.6 Solution Blending of Polystyrene and MESO 81
3.2.7 Processing Technique (Casting) 82
3.2 8 Stress-Strain Experiment 82
3.2.9 Viscosity Measurements 83
CHAPTER FOUR
RESULTS 84
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CHAPTER FIVE
DISCUSSION
5.1 The iodine number and epoxy contents 106
5.2 Mechanical properties of the blends 106
5.2.1 Tensile strength 107
5.2.2 Young‘s modulus of elasticity 107
5.2.3 Elongation-at-break 108
5.3 FT-IR characteristic bands‘ Comparison of spectra table 4.3, 4.4, and 4.5 108
5.4 Viscosity measurements 109
5.4.1 Relative viscosity 109
5.4.2 Reduced viscosity 110
CHAPTER SIX
SUMMARY, CONCLUSION AND RECOMMENDATIONS
6.1 SUMMARY 112
6.2 CONCLUSION 113
6.3 RECOMMENDATIONS 114
6.4 CONTRIBUTIONS TO KNOWLEDGE 114
REFERENCES 115
APPENDICES 119
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CHAPTER ONE
1.1 INTRODUCTION
Vegetable oils are agricultural products derived from the seeds of many plants such as soybean, castor, neem, rubber, coconut, melon, jatropha, palm, olive oil trees e.t.c. Different plant seeds contain different volume of vegetable oil per kilogram of seeds‘ weight. Within the same plant seeds, the difference in species of seeds also gives rise to difference in the volume of vegetable oil per kilogram of that species.Vegetable oils contain triglyceride molecule. Other constituents of vegetable oils include; tocopherol, lignins, and vitamin E. Generally, all vegetable oils contain the same molecular morphology of triglyceride in terms of shape but different in fatty-acids composition and distribution within the triglyceride molecule. The end-use applications of vegetable oils in foods, cosmetics, pharmaceuticals, polymer industries e.t.c. depend (among other factors) on the difference in fatty-acids composition and distribution within the triglyceride molecule. This is an optimization technique often referred as structure-property relationship (SPR) or quantitative structure activity relationship (QSAR). Based on this technique, vegetable oils are classified as; edible and non-edible, drying, semi-drying and non-drying. Vegetable oils in their raw-form, may find direct end-use application, or may need refining or chemical modification for better end-use application, all depending on the physicochemical property of interest and engineering design. Chemical modification such as epoxidation can serve as a precursor route for synthesis of bio-based industrial chemicals such as glycols, lubricants, plasticizers, stabilizers e.t.c,(Taydeet al 2012).
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For an example, in an engineering design aimed at end-use properties of plasticization and stabilization for application in polymer industry, vegetable oils may be subjected to chemical or/and chemo-physical modification such as epoxidation, cationic polymerization, copolymerization or blending with petro-chemical product.Epoxidized vegetable oil such as epoxidized soybean oil (ESO) resin, has disappointing thermo-mechanical properties for practical applications in terms of load bearing capacity.Park et al (2003) synthesized epoxy resin from soybean oil and castor oil and found that glass transition temperature was less than 500C.Javniet al(2004) prepared polyurethane foam from soybean oil derivative and the result indicated that the useful thermo-mechanical properties of the oil base resin were depended strongly on incorporation of rigid petroleum product, especially when the rigid content was 50% and above.Sharif et al (2001) used Differential Scanning Calorimetry (DSC) to determine the glass transition temperature of leen seed oil epoxy/polystyrene polyblend, and found that only single Tgwas observed indicating homogenous miscibility of constituents of the blend at all ratios.Mamza and Folaranmi(1996) also found that polystyrene and polyvinylacetate were miscible in both polar and non-polar solvents such as chlorobenzene, tetrahydrofuran and toluene.Ashratet al(2007) observed that the tensile strength, as well as elongation-at-break increased with increasing polystyrene content in leen seed oil epoxy/polystyrene (LOE/PS) polyblend. Thus, LOE increases flexibility and plasticity of polystyrene enormously. The blend structure shows the tensile strength behaviour similar to low-density polyethylene.Therefore, to obtain acceptable thermo-mechanical properties for practical application especially in terms of load bearing capacity, the epoxidize soybean oil should be modified either by copolymerisation, blending or reinforcement.
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Cationic polymerization of double bonds of triglyceride molecule gives a very low molecular weight polymer with the subsequent attendance poor thermo-mechanical properties, resultantly unsuitable for an engineering design aimed at end-use properties of tensile strength, thermal stability and good processing temperature for application in polymer industries.Thus, vegetable oils alone, despite its merits such as biodegradability, eco-friendliness, sustainability, renewability e.t.c against the petroleum products(crude oil) counterpart and cannot be used to achieve satisfactory thermo-mechanical properties.Therefore, progression is on-going in compromising both merits and demerits of vegetable oil and crude oil respectively for suitable end-use properties and applications
1.2 RESEARCH PROBLEM/BACKGROUND OF THE STUDY
Local Content Utilization and Diversification
Most industrial raw materials used in Nigeria polymer industries are petroleum products. Most of these petro-based raw materials such as epoxides are imported. Thus, foreign currencies are needed to source these raw materials which consequently mount pressure on local currency with attendant devaluation. However, since fossil fuel depletes with time amidst its demerits such as non-biodegradability, environmental hazards, and high cost, efforts are in progress to reduce crude oil dependence for revenue generation as well as industrial based raw-materials due to its negative effect on climate change. Thus, agricultural products which are sustainable, biodegradable, renewable and low cost, offer a promising alternative to crude oil. Thus, an agricultural product, such as vegetable oils can be diversified into many industrial raw-materials (e.g epoxides) amidst its domestic usages
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1.3 JUSTIFICATION OF THE STUDY
Among many monetary policies of Central Bank of Nigeria to remedy the foreign exchange cisis, is the direct U.S dollar sell to manufacturers under the umbrella of Manufacturing Association of Nigeriato boast productivity and reduce the resultant pressure effect on Naira. However, thesemonetary policies have not yielded the expected results as dollar demand continued on increase amidst its paucity with subsequent devaluation of Naira and resultant economic recession. Thus, epoxyl resins of soybean oil as a precursor for synthesis of many industrial chemical products will not only reduce U.S dollar demand for industrial chemical products to safe Naira, but also increases the gross domestic products andreduces environmental hazards associated with petroleum products.
1.4 SCOPE (LIMITATION) OF THE STUDY
High cost and non-availability of some chemical reagents within Zaria limits furtherstudy on the conversion of the oxirane-oxygen to other functional groups.
1.5. AIM AND OBJECTIVE OF THE STUDY
The aim of the study is to produce and determine the compatibility of blends of thermally cured epoxyl resin of soybean oil with polystyrene.
The specific objectives of the study are to:
(i) Determine the iodine number of soybean oil.
(ii) Epoxidize the soybean oil and thermal curing of epoxidized soybean oil (MESO).
(iii) Produce varying blends of polystyrene and MESO.
(iv) Determine the viscosity and mechanical properties (Young‘s modulus, tensile strength and elongation-at-break) of blends and access the compatibility of the blends.
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