Blends of phthalic anhydride-modified palm stearin alkyds with high carboxylic acid contents with epoxidized natural rubber



Solution blends comprised of alkyd having high carboxylic acid ([BOND]COOH) content and epoxidized natural rubber (ENR 50, having nominally 50% of the isoprene units converted to epoxide groups) are self-crosslinkable at 30°C in toluene solution. Two modified palm stearin alkyds with different amounts of [BOND]COOH groups were synthesized by reacting phthalic anhydride with alkyd containing excess hydroxyl ([BOND]OH) groups under controlled conditions, leading to the formation of different amounts of [BOND]COOH as side-chains. The crosslinking reactions between the alkyds and ENR 50 in toluene solutions were investigated using FTIR and DSC. The compatibility between ENR 50 and alkyd was indicated by the presence of a single glass transition temperature (Tg) in the blend. Intercomponent crosslinking reactions have occurred between the epoxide groups of ENR 50 and [BOND]COOH groups of alkyd with the formation of ester linkages. The crosslink density is proportional to the amount of [BOND]COOH groups in the alkyd. As the [BOND]COOH content is increased, the blend produces higher percentage of gel insoluble in toluene. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013