DEVELOPMENT OF SURFACE COATINGS USING POLYESTER RESIN FROM CASHEW NUT SHELL LIQUID DERIVATIVES

Abstract

Cashew Nut Shell Liquid (CNSL) is a by-product of the cashew nut industry waste. CNSL contains several phenolic compounds such as cardol, anacardic acid, cardanol, and methyl cardol. It is a dark reddish brown liquid and is an excellent source of natural resin. This research aims at developing surface coatings based on synthesized polyester resin from cardol, a derivative of CNSL. Polymerization of cardol with maleic anhydride was done under acidic conditions to formulate a polyester resin, which was dissolved in ethyl acetate solvent to develop surface coatings. The developed coating was found to have moisture content of less than 1%, viscosity (194.96 mm2/s), color (brown), specific gravity (1.978), acid value (12.7 mg KOH/g), iodine value (233.43 mg iodine/100g). FTIR analysis showed the presence of O-H stretching of the phenol, C=C aromatic ring vibration and C=O stretch. Tests done on commercial coatings from Dura Coat and Crown Paints showed presence of a broad peak observed in the region above 3000cm-1 and was attributed to O-H stretch in phenols. The acid value was 10.5 mg KOH/g and had an iodine value of 243 mg iodine/100g. The color and viscosity varied while the moisture content was less than 1%. The investigation showed that the developed coating was of superior quality and could be comparable to the commercial coatings in the market.