Slow decomposition of silicone rubber

The sol content of previously extracted samples of lightly crosslinked silicone rubber has been found to increase during prolonged storage under relatively mild conditions. Simultaneously, the tensile stress slowly decreases in samples held stretched, and the equilibrium degree of swelling increases somewhat. Thus, the polymer network appears to undergo slow decomposition. This process is accelerated by moisture, by ammonia vapor, and by raising the temperature of storage. It is slowed down by prior treatment of the polymer with a silazane reagent which reduces the number of residual OH groups. It is therefore attributed to hydrolytic decomposition of the poly(dimethylsiloxane) molecules initiated by OH groups.