Abstract

Alcoholysis-polyesterification method was used in the investigation of utilization of Ximenia americana seed oil in the formulation of alkyd resins. The extracted oilseed gave an oil yield of 45.7% (w/w) and the physicochemical characterization indicated it is semi-drying in nature with iodine value of 152.3 g I₂ 100 g^-1. The fatty acid analysis of the oil carried out earlier revealed oleic and linolenic as dominant fatty acids, having values of 72.1 and 10.3% respectively. Four grades of alkyds were formulated at 40% (I), 50% (II), 60% (III) and 70% (IV) oil lengths. The reaction progression was followed by determining the acid value of the aliquots for the reaction mixture at various time intervals beside the volume of water evolved. Kinetic studies showed that the reaction was second-order with values of 3.12 x 10^-4, 2.44 x 10^-4, 2.3 x 10^-4 and 2.28 x 10^-4 g (mg KOH)^-1 min^-1 for samples I, II, III and IV respectively. The extent of reaction (% P_av) determined at the initial stage of reaction ranged from 63.3 to 78.6%, indicating an appreciable degree of conversion. The corresponding average degree of polymerization (D_p) ranged from 2.7 to 4.7 and this indicated the formation of high molecular weight alkyd. Characterization of the alkyd gave iodine value of 70.1 + 0.74, 76.1 + 1.05, 81.2 + 1.0 and 86.3 + 0.8gI₂100g^-1 for samples I, II, III and IV respectively. The corresponding saponification values were 297.5 + 1.5, 332.5 + 1.2, 378 + 1.1 and 420.2 + 1.3 mg KOH g^-1. The 40 and 50% oil length alkyd films were resistant to acid, brine and water with little resistance to alkali. Characterization of paint based on two alkyd resin derivatives, 40 and 50% oil lengths, gave values for surface drying and tack-free property of less than 2 and 5 hours respectively in respect of the 40% oil length.

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