Influence of aging medium on recovery behaviors of CR/NR composite from circular deformation

This study examined the recovery behavior from the circular deformation of a thermally aged CR/NR composite. A linear sample of a rubber vulcanizate was made into circular form by fixing both ends of the sample with a pin and aging it thermally in air and distilled water. The recovery increased with the time after removal from circular deformation. The recovery decreased with increasing aging temperature and time. Recovery of the sample aged in air was smaller for long measurement times than that of the sample aged in distilled water. The difference in the recovery behavior of the samples aged in air and distilled water can be explained by changes in the crosslinking density and the annealing effect of the aging medium. The instantaneous recovery was obtained by extrapolating the linear recovery variations. They also showed a good linear relationship with the aging time. The recovery behavior at ambient temperature could be predicted using the experimental results of the accelerated thermal aging. In terms of the instantaneous time, it was predicted that the service lifetime of the sample aged in air at ambient temperature would be much longer than the sample aged in water.