EFFECT OF INTERFACIAL BONDING ON THE SELF-ADHESION OF SBR AND NEOPRENE

When two elastomer layers are partially crosslinked in contact with each other, the strength of adhesion increases. This effect has been studied for simple vulcanizates of SBR (styrene-butadiene rubber) and for neoprene vulcanizates crosslinked with sulfur and/or oxide linkages. Under threshold conditions, i. e. , at high temperatures and in the swollen state, when both viscous effects and strain-induced crystallization are virtually eliminated, the work of detachment is small and approximately proportional to the inferred degree of interlinking. The principal structural factors governing the adhesive strength under threshold conditions appear to be the number and length of the molecular strands comprising the network and crossing the interface. The threshold fracture energy is directly proportional to the density of such strands and is smaller for shorter strands.