ABSTRACT
In this research, the extraction, characterization of chitin and chitosan from desert locust (Schistocerca gregaria) were carried out, followed by grafting of acrylic acid to chitosan which was then used as modifying additive to emulsion paint. Chemical demineralization, deproteinization and decolourization were carried out to obtain the chitin followed by deacetylation to obtain the chitosan. Acrylic acid was then grafted onto the chitosan to obtain chitosan-grafted-acrylic acid which was then used as additive to produce modified emulsion paint. The following analyses were carried out; density, solubility test, ash content, moisture content, degree of deacetylation, Fourier transformed-Infrared spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), Scanning electron microscopy (SEM), viscosity, drying time, alkalinity test, crosscut test and bend test. The results obtained showed 90.06 % degree of deacetylation of the chitosan, 6.00 % moisture content of the chitosan, 2.24 % ash content of the chitosan, 81.75 % grafting percentage, 72.69 % grafting efficiency, 2360.60 cm−1 and 2344.61 cm−1 peaks are attributed to the carboxylic acid functional group which indicate the point of grafting of the acrylic acid unto the chitosan, the glass transition temperatures obtained from differential scanning calorimetry were 152.88 0C, 229.63 0C and 98.53 0C for chitin, chitosan and chitosan-grafted-acrylic acid respectively. Surface morphology of the chitin shows prominent microfibrils and porous structures while erosion of some of the microfibrils and porous structure on the chitosan was observed which could be attributed to successful deacetylation of the chitin to chitosan whereas the chitosan-grafted-acrylic acid shows the coverage of the little microfibrils and porous structure. Also the overall performance of the modified paint shows increase in density, viscosity, bendability, resistance of the paint coatings to separation from substrates when the right angle lattice patterns were cut into it and decrease in the drying time,
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alkalinity and the filler content. The chitosan-grafted-acrylic acid obtained was incorporated into emulsion paint; this was assessed with respect to another emulsion paint produced without chitosan-grafted-acrylic acid and a commercial paint. Tests such as drying time, density, viscosity, bend test, ash test, acidity or alkalinity test and cross-cut test were carried out and it was discovered that the paint with chitosan-grafted-acrylic acid had remarkable improvements in its properties.
TABLE OF CONTENTS
Title Page .………..…………………………………………….……………..….… i Declaration …………………………………………………………………………. ii Certification ………………………………………………..…………………….… iii Dedication ………………………………………………….……………………… iv Acknowledgements …………….…….……………………….….…………………. v Abstract ……………………………………………………………………….…… vi Table of Contents …………….………………………………..…………….……. viii List of Figures …………..………………………………………………………..…. xiii List of Tables …………..……………………………………………………….…. xiv List of Plates ………………..………………………………….……..……………. xv Abbreviations …………………………………….……………………………….. xvi CHAPTER ONE 1.0 INTRODUCTION …………………………………….…………………… 1 1.1 Background ………………………………………………………………… 1 1.2 Statement of the Research Problem …………………..…………………. 3 1.3 Aim and Objectives ……………………………………………………….. 3 1.4 Justification of the Study ……………………………….………….……… 4 1.5 Scope ……………………………………………………..………………….. 4 CHAPTER TWO 2.0 LITERATURE REVIEW ………………………………………………… 5 2.1 Basic Components of Paint ……………………………………..…………. 5 2.1.1 Binder (or film former) ………………………………….…………….…….. 5
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2.1.2 Diluent or Solvent ………………………………………………….….…….. 7 2.1.3 Pigment and Filler …………………………………………………………… 7 2.1.4 Additives …………………………………………………………….………. 9
2.2 Qualities of Paint ………………………………………..………………….. 9 2.2.1 Hiding ……………………………………………………………………..… 9 2.2.2 Appearance …………………………………………….…………………… 10 2.3 Classification of Paints ………………………………………….………… 10 2.3.1 Water-thinned Paints ………………………………….……………….…… 10 2.3.2 Alkyd Paints (Gloss or Oil Paints) ………………………………..………… 11 2.4 Methods of Application of Paints …………………………..……..…… 13 2.5 Drying of Paints ………………………………………….…………………. 14 2.5.1 Drying without Chemical Reaction ………….……………..……………….. 14 2.5.2 Drying by Chemical Reaction ……………..……………………….………… 15 2.6 Acrylic Polymers …………………………………………………………….. 15 2.7 Chitin …………………………………………………………………..……. 16 2.7.1 Chitin Extraction ………………………………………………………..…… 18 2.7.2 Demineralization ……………………………………………………………… 19 2.7.3 Deproteinization of Chitin …………………………………………….……… 19 2.8 Crystalline Structure of Chitin …………………..………………………… 20 2.9 Deacetylation of Chitin to Chitosan ………………………………………… 21 2.10 Chemistry and Properties of Chitosan ………………………….…………. 22 2.10.1 Characteristics of Chitosan ……………………………………………….…… 22 2.10.2 Determination of the Degree of Deacetylation (DD) ………………….……. 23 2.10.3 Viscosity …………………………………………….……………….……… 24 2.10.4 Solubility ……………………………………………………………………. 25
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2.10.5 Emulsification ………………………………………………………………. 27 2.10.6 Crystalline Structure of Chitosan …………………………………………… 27 2.11 Ash Content …………………………………………………………………. 27 2.12 Applications of Chitosan …………………………………………………… 28 2.12.1 In the Wastewater Treatment …………………………………………..…… 28 2.13 Grafting onto Chitosan ……………………………………….……..…….. 29
2.14 Graft Copolymerization …………………………………………………… 30
CHAPTER THREE 3.0 MATERIALS AND METHODS …..……………………………………… 33 3.1 Materials ………………………………..…………………………………………. 33 3.1.1 Equipment and Apparatus ………………………………..……………………. 33 3.1.2 Chemical/Reagent …………………………………………………………… 34 3.2 Locust Sampling ………………………………………………………..…… 34 3.3 Extraction of chitin ………………………..………………………………. 35 3.3.1 Demineralization ………………………….……………….………………… 35 3.3.2 Deproteinization …………………………………..……….………………… 35 3.3.3 Decolourization ………………………………….…………………………… 35 3.3.4 Deacetylation of the chitin ………………………………….………………… 35 3.4 Characterization of the chitin, chitosan and grafted chitosan ………..…. 36 3.4.1 Fourier transformed infrared spectroscopy ………………….………….…… 36 3.4.2 Differential Scanning Calorimetry ………………….…………..…………… 36 3.4.3 Scanning Electron Microscopy ………………..………………….………… 36 3.5 Degree of Deacetylation ……………………………………………………. 36 3.6 Solubility ……………………………………………………….…………… 37
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3.7 Moisture Content ……………………………………………..….………… 37 3.8 Ash content …………………………………………………………..………. 38 3.9 Graft Copolymerization ………………………………….……..………….. 38 3.9.1 Evidence of grafting ………………………………………………………… 40 3.10 Preparation of emulsion paint ……………………..…………….……….. 40 3.10.1 Procedure (Preparation of Emulsion paint) ….………….……….……….…… 41 3.11 Analyses of the paints ………………………….……………..……..…….. 41 3.11.1 Density (ASTM 1475) ……………………………………………………….. 41 3.11.2 Drying Test (ASTM D711) ………….…………………….……..…………. 41 3.11.3 Viscosity Test …………………………………………….…………….…… 41 3.11.4 Cross-cut test of the paints (ISO 2409) ……………………….…………….. 42 3.11.5 Bend Test ……………………………………………………….………..…… 42 3.11.6 Acidity or Alkalinity Test ………………….………………………..……..… 42 3.11.7 Ash Test for the Paints (ASTM D2584) ………………………….……….… 42 CHAPTER FOUR 4.0 RESULTS AND DISCUSSION ……………………………………….…….. 43 4.1 Degree of Deacetylation (DD) …………………………………….………… 43 4.2 Solubility ……………………………………………………………………. 43 4.3 Moisture Content …………………………………………………….…….. 44 4.4 Ash Content …………………………………………………………….…… 44 4.5 Graft Copolymerization ………………………………………….………… 44 4.6 FTIR analysis …………………………………………………………….… 45 4.6.1 FTIR of Chitin ………………………………..……………….…………. 45 4.6.2 FTIR of Chitosan ……………………..……………….………….……… 45
4.6.3 FTIR of chitosan-grafted-acrylic acid ………..……………….….………. 46
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4.7 SEM analysis ………………………………………………………………… 47 4.7.1 SEM of Chitin ……………………………………………………………….. 47 4.7.2 SEM of Chitosan …………………………………………………………….. 48 4.7.3 SEM of Chitosan-grafted-acrylic acid ……………………………………….. 48 4.8 Differential Scanning Calorimetry ……………………….………………. 49 4.8.1 DSC of chitin …………………..………………………..….………………… 49 4.8.2 DSC of chitosan …………….………………………….………………….… 50 4.8.3 DSC of chitosan-grafted-acrylic acid ………………………..……………….51 4.8.4 Superimposed DSC thermographs of Chitin, Chitosan and Chitosan- grafted-acrylic acid …………………………………………………….…….52 4.9 Paints ………………………………………………………………………… 53 4.9.1 Densities of the paints ……………………………………………………….. 53 4.9.2 Drying time of the paint samples ……………………………………………. 53 4.9.3 Cross-cut test ………………………………………………………………… 54 4.9.4 Acidity or alkalinity test …………………………………………………… 54 4.9.5 Viscosity test ………………………………………………………………… 55 4.9.6 Bend test …………………………………………………………………… 55 4.9.7 Ash test for the paints (ASTM D2584) ………….………………………… 55 CHAPTER FIVE 5.0 Summary, Conclusion and Recommendations …….…………………… 57 5.1 Summary ……………………..………………………….………………. 57 5.2 Conclusion ………………………………………………………..……… 58 5.3 Recommendations ………………………………………………..……… 58 REFERENCES …………………………………………………………………. 59
APPENDICES …………………………………………………….……………. 68
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CHAPTER ONE
INTRODUCTION 1.1 BACKGROUND Paint is any liquid, liquefiable, or mastic composition that, after application to a substrate in a thin layer, converts to a solid film (Obi, 2013; Ghamande et al., 2016). It is most commonly used to protect, colour, or provide texture to objects. Paint can be made or purchased in many colours and in many different types, such as watercolour, synthetic, etc. Paint is typically stored, sold, and applied as a liquid, but dries into a solid (Lambourne and Strivens, 1999). In formulating paint for a particular purpose it will be essential for the formulator to know the use to which the painted article is to be put, and physical or mechanical requirements they are likely to be called for (Lambourne and Strivens, 1999). Many industrial sectors use organic solvents widely (Ridgwaya et al., 2003). Nervous system damage (central and peripheral), kidney, and liver damage, adverse reproductive effects, skin lesions, and cancer, are the major health impacts associated with organic solvent exposure (National Institute for Occupational Safety and Health, 1977). They can also cause death from acute exposure, leading to depression of the brain’s respiratory centre and/or cardiac arrhythmias. Solvents share many chemical, physical, and biological properties, which warrant that national attentions need to be directed to them as a group. In addition, many solvent groups or individual substances have special properties that require specific control measures (Jafari et al., 2008). Solvents are one of the most important components of paint and have the major purpose of reducing (thinning) paints to a suitable handling consistency or viscosity for ease of manufacture and application. After the paint has been applied, the solvent evaporates and leaves the dry paint film on the substrate. In paint production, solvents
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vapours are emitted throughout the manufacturing process. If these emissions are left uncontrolled, high concentrations of organic solvents can build up in the work area, compromising workers‘ health and safety (Williams et al., 2007).
In the living environment, sick-building syndrome is a social health problem which occurs when the quality of indoor air diminishes due to harmful substances contained in it (European Commission Joint Research Center for Environment Institute 1997). Volatile Organic Compounds (VOCs) such as formaldehyde cause sick-building syndrome because VOCs are contained in furniture and building materials (Imai and Motohashi, 2003). To combat this problem, a considerable number of studies have been done to improve indoor air quality (Uedaira et al., 2003; Miyamura, 2003). In interior materials, both the decomposition of formaldehyde using photocatalysts such as titanium oxide, and decomposition using chemical means or the physical adsorption of formaldehyde, have been studied (Miggli et al., 1998; Obee and Brown, 1995; Ching et al., 2004; Gesser and Fu, 1990; Motohashi and Imai, 2003; Santamaria, et al., 2004). Although the means for decomposing formaldehyde are effective, if sufficient ultraviolet radiation cannot be supplied throughout the indoor environment, undecomposed formaldehyde remains. In the case of physical adsorption with porous raw materials such as zeolite, diatomite, and charcoal, there is a problem in that adsorbed formaldehyde is emitted. On the other hand, chemical adsorption by reactions with formaldehyde can be efficiently removed and not re-emitted. Chemical adsorbents, however, are not sufficiently safe (Wada et al., 2005).
Recently, investigations using natural raw materials as adsorbents were carried out. Among the natural raw materials, chitosan is an environmentally friendly material with many superior properties. Chitosan powder was used to inhibit the emission of formaldehyde from plywood (Sato, 1996; Sato et al., 1997). Ishimaru also reported that
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chitosan is effective in adsorbing formaldehyde (Ishimaru, 2001). Chitosan is a polysaccharide consisting of 2-amino-2-deoxy-D-glucopyranose as a repeating unit and is obtained by deacetylation of chitin. Chitin exists in crustacean shells, such as crabs and shrimps; in insects, such as beetles and grasshoppers; in cuttlefish bone; and in the cell walls of fungi, such as mushrooms. Compared to synthetic polymers, chitosan has several important advantages, including biocompatibility, biodegradability, and no toxicity. In addition, chitosan has reactive amino groups on pyranose rings and becomes a cationic polymer upon the protonation of its amino groups. However, chitosan simply added to waterborne coatings cannot uniformly disperse. Furthermore, when chitosan-acid solution is added to waterborne coatings using acrylic emulsions, precipitates are formed because chitosan is a cationic polymer (Wada et al., 2005). 1.2 STATEMENT OF THE RESEARCH PROBLEM Volatile organic compounds (VOCs) such as formaldehyde cause sick-building syndrome because VOCs are contained in furniture and building materials. To the best of my knowledge, there has been no report on the production of emulsion paint obtained by incorporating a binder synthesized by grafting chitosan obtained from locust with acrylic acid to produce paint with improved properties. 1.3 AIM The aim of this research is to produce emulsion paint with improved properties by incorporating binder obtained by grafting acrylic acid onto chitosan from desert locust. OBJECTIVES The specific objectives of this research include:
i. Extraction of chitin from desert locust (Schistocerca gregaria)
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ii. Conversion of chitin to chitosan
iii. Grafting of chitosan with acrylic acid through free radical mechanism in order to obtain suitable binder.
iv. Characterization of the samples using FTIR, SEM and DSC.
v. Production of emulsion paint with the chitosan-grafted-acrylic acid and without chitosan-grafted-acrylic acid.
vi. Analyses of modified and unmodified emulsion paints produced and compare with commercial emulsion paint for properties such as drying time, density, viscosity, bend, ash, acidity or alkalinity and cross-cut.
1.4 JUSTIFICATION OF THE STUDY Desert locust is generally known to be a destroyer of green plants and copolymerization of chitosan obtained from desert locust with acrylic acid for use in emulsion paint will help to create job opportunities. 1.5 SCOPE The scope of this research is focused on the extraction and characterization of chitin and chitosan from locust, grafting of the chitosan with acrylic acid in order to obtain suitable binder, production of emulsion paint with and without the chitosan-grafted-acrylic acid and evaluation of some properties of the emulsion paints produced and compared with those of commercial emulsion paint.
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