MOISTURE CURE AND IN-SITU SILICA REINFORCEMENT OF EPOXIDIZED NATURAL-RUBBER

Epoxidized natural rubber (ENR) was first precured with 3-aminopropyltriethoxysilane (APS) by the normal compression molding technique. The resultant sheet was further subjected to moisture cure, via hydrolysis and condensation reactions, by soaking it in water. The moisture-cured sample, when prepared under appropriate reaction conditions, demonstrated partial strain-induced crystallization behavior and moderate tensile strength, as opposed to typical peroxide-cured and sulfur-cured vulcanizates. The suitability of the ENR-APS precured sample for in-situ silica reinforcement by the sol-gel process, using tetraethyl orthosilicate (TEOS) as the silica precursor, was also demonstrated. Silica content as high as 36% by weight could be incorporated into the rubber, and TEOS-to-silica conversion of over 60% was observed Comparative analysis with a typical peroxide-cured sample that was subjected to the same sol-gel process indicates that the silica in the final ENR-APS sol-gel vulcanizate is chemically bound to the rubber network.