INVESTIGATIONS FOR PHASE BONDING OF PRECU RED POLYMERS

Employing a modified T-Peel-Test it is shown that on covulcanization i nterfacial bonding occurs between a precured elastomer and a fresh rub ber mixture if both consist of the same type of polymer (e. g. SBR1500 ). Crack initiation and propagation always proceeds in one of the poly mer phases, not in the interface. Diffusion of curing agent into the p recured elastomer gives rise to a step-like variation of crosslink den sity near the interphase, resulting in areas of net over-or undercurin g in the vicinity of the interfacial border. Based on a concept of fra cture mechanics the point of crack is interpreted with respect to the degree of crosslinking in the precured elastomer and the concentration of curing agent in the mixture. If incompatible systems are used, an increasing amount of adhesive fractures right at the interfacial borde r is observed due to a lacking or less prominent interphase.