Stress Relaxation in Compression of Rubber and Synthetic Rubber Vulcanizates Immersed in Oil

Abstract

Abstract The practical implications of this study are that rubber compounds which swell in the presence of oil have a property which may be utilized in some applications where it may serve a useful purpose. Examples are O-ring seals and other types of gaskets, where the rubber is used in compression. In these cases the stress decays more slowly with time, and in some cases the force would increase, and the tendency to leakage would be minimized. In these experiments the sample was relatively unconfined except for the direction of loading with only low frictional forces which tended to prevent increase in volume. It was noted (Figures 4 and 6) that, with natural rubber and GR-S at 70° C the stress reached a maximum between 1000 and 10,000 hours, which is a result of the sample reaching equilibrium with respect to swelling by the oil, and the stress then decreases, depending on the oxidative scission of bonds in the same manner as found for tests conducted in air. However, according to Scott, the attack of swelling agents accelerates oxidation; so it is possible that this oxidative scission might be in addition to that normally measured in air.