Crosslinking of partially neutralized liquid rubbers containing terminal and pendent carboxyl groups with anhydride and bisepoxide

Crosslinking of partially neutralized liquid rubbers containing terminal and pendent carboxyl groups with anhydride, and bisepoxide was investigated by the carboxyl–anhydride-epoxide reaction. The partially neturalized liquid rubbers were prepared by the partial neutralization with MgO and CaO from a butadiene (BD)–acrylonitrile (AN) copolymer (Hycar CTBNX 1300X9) with the functionality of 2.4. Bisphenol-A diglycidyl ether (BADG) was the bisepoxide used, and hexahydropthalic anhydride (HPA) was the anhydride used. The metal carboxylate groups in the system catalyzed the curing reaction. The metal-containing cured rubbers obtained showed considerably higher tensile strength than the previously reported metal-containing cured rubbers based on CTBN 1300XB (BD–AN copolymer) with the lower functionality of 1.8. In addition, the cured rubbers generally showed higher water resistance, and lower weight gains in benzene, dioxane, and n-hexane than the CTBN-series ones. Thermal behavior and stress relaxation are also discussed.