ADHESION OF UNVULCANIZED ELASTOMERS

The self-adhesion and mutual adhesion of various unvulcanized elastomers have been studied as a function of contact time and temperature by means of peel tests. Peel energies were measured at a constant rate at ambient temperature (approximately 23-degrees-C). The self-adhesion of all the elastomers except natural rubber and polybutadiene was found to be time-dependent over the time scales covered, reaching the cohesive strength if sufficient contact time was allowed These observations appear to be consistent with a chain diffusion mechanism. The mutual adhesion for some pairs of dissimilar materials (all of which were immiscible) also increased appreciably with time, approaching the cohesive strength of the weaker adherend, whereas for others it did not. The time scale for development of strong adhesion tended to be longer in the case of mutual adhesion than for the self-adhesion of the corresponding materials. In one case polar interactions are believed to be responsible for the strong mutual adhesion. In other cases, it appears that limited interdiffusion (near the interface) may lead to strong mutual adhesion.