SYNTHESIS, CHARACTERIZATION AND EVALUATION OF EPOXY / GUAR–GUM BASED POLYMER COMPOSITES

Abstract

Now a days polymer from renewable resources have been attracting increasing attention, primarily for two major reasons: environmental concerns and the realization that our petroleum resources are finite. A third reason for growing interest in polymers from renewable resources relates to adding value to agricultural products, which is economically important for many countries. Generally polymer from renewable resources can be classified into three groups: 1) Natural Polymer such as starch, Protein and cellulose, Guar Gum : 2) Synthetic Polymer from natural resources such as Poly (Lactic acid ): 3) Polymer From Microbial Fermentation such as Poly (hydroxy butyrate). [1]. A major advantage of all these materials is that they are biodegradable and that their final productof degradation are environment friendly. As with numerous Petroleum based polymers many properties can be improved through appropriate blending and composite formulation. These new blends and composites are extending the utilization of polymers from renewable resources into wider applications.Guar gum or guaran is a non-ionic, branched polysaccharide extracted from endosperm of the seed of "Cyamopsistetragonolobus", family leguminosae, which grows naturally in the arid regions of the Indian subcontinent and is now also commercially grown in North Africa and South America. Guar gum is a galactomannan, structurally consisting of 1,4 - β- D ~ mannopyranosebackbone with branch pointsrandomly distributed from their 6-positions linked to 1- α - D - galactopyranose units [4-6]. Galactomannans can often be used in different forms for human consumption.featuring different physicochemical properties, galactomannans are a versatile material used for many applications; they are excellent stiffeners and stablizers of emulsions, and the absence of toxicity allows their use in the textile, pharmaceutical, biomedical, cosmetics and food industries[50, 51], Recently new and alternative souces of galactomaannans have been characterized [52, 53], and some works showed the possibility of using galactomannan to the formation of films and coatings [54-57].However in a very few studies conducted investigating the use of these material as fillers in polymer composites. Guar gum and Hydroxy propyl guar gum were successfully used a reinforcing filler in epoxy based composites. Native guar gum is usually not used as such industrially because of a variety of iii reasons such as its susceptibility to enzyme hydrolysis and bacterial attack and the difficulty in controlling its solution viscosity so in order to overcome these this problem chemical modification of the parent polysaccharides is carried out. One such method is its reaction with allyl chloride in the presense of analkali [31].Which result in a derivative with reduced molecular weight allylated guar gum are more soluble in water, resulting in clearer solutions while the viscosity decreases to some extent. The degree of allylation greatly affects the properties of the polysaccharides. The degree of substitution of allyl guar gum were determined by titration analysis. The Present work aims at preparing a polymer composites, which is cost effective, meeting the desired properties requirement and obtained from natural material. Guar gum was etherified using a Williamson synthesis reaction using allyl chloride. The synthesized allyl guar gum with varying degree of substituition were characterized for their Chemical and thermal properties. The allyl guar gum has been characterized through FTIR, and 1H NMR methods. The Morphology of the allyl guar gum were studied by Scanning Elecrtron Microscope.The addition of allyl guar gum with varying degree of substitution were incorporated as filler in an epoxy resin to study the effect of degree of allylation on the mechanical properties including Tensile Strength, % Elongation at Break and Flexural Strength of the composites were evaluated . In all these instances the optimum concentration of allyl guar gum was ascertained with respect to the mechanical and thermal properties (Thermogravimetric analysis and Dynamic Mechanical Analysis) of resultant composites. The morphological properties of the resultant composites were studied by Scanning Electron Microscopy. The storage modulus of the resultant composites were increased only at lower concentration. The Tg values obtained from Tan d initially increased and then decrease with concentration as well as the extent of allylation. Guar gum are generally subjected to modification via grafting reactions using a number of initiators techniques including Peroxides, Persulphates, redox system and microwave radiation. In the Present work Allyl guar gum has been grafted with acrylic acid by using Ferrous ammonium sulphate and Hydrogen peroxide as redox pair. The synthesized Allyl guar gum-g-Polyacrylic acid with varying carboxyl value has been characterized for their chemical and thermal properties. The carboxyl value of allyl Guar gum –g- Poly Acrylic acid has been obtained through titrimetric analysis. The effect of addition of allyl guar gum–g-Polyacrylic acid in the epoxy matrix on the mechanical, chemical and thermal properties of the composites were iv also investigated. The inclusion of allyl guar gum –g-polyacrylic acid (0.033, 0.019 ) into epoxy matrix resulted in an increase in Tensile , flexural strength of the composites , while the % elongation of the resultant composites increases as the carboxyl value of the composites gets increases , however the thermal stability of resultant composites gets decreases with the decrease in carboxyl value of the resultant composites .The storage modulus of the resultant composites increase with carboxyl value while the glass transition of the composites decreases with the carboxyl value.