Search Results

In developing engine oils, it is crucial to consider their compatibility with the rubbers used for seals. Among the different seal rubbers, silicone rubber is particularly susceptible to attack by acids and bases, which means it would be more likely to be affected by certain engine oil additives. In this study, the effects of some major additives, namely detergents, zinc dialkyl-dithiophopshate (ZDDP) and molybdenum dithiocarbamate (MoDTC), on silicone rubber were investigated. Silicone rubber test specimens were immersed in sample oils containing these additives for a prescribed period at 150°C, then the physical properties of the test specimens were measured to compare the effects of the different additives. It was found that ZDDPs dramatically reduce the tensile strength of silicone rubber, with primary ZDDP having a greater effect than secondary ZDDP.

We developed a measurement method to evaluate the sealing performance for narrow gap between a metal shaft and a fitted sleeve quantitatively in a brief time. We examined the effect of the chamfer shape and the surface roughness of the shaft on the leakage rate. We also conducted liquid leakage test in order to compare the leakage rate of gas with that of the liquid. From this comparison, we showed that it is possible to evaluate the sealing performance for liquid by measuring leakage rate of gas. In addition, we discussed the leakage rate of fluid through the gap by assuming viscous flow. The estimated leakage rate of the liquid derived from the leakage rate of air by converting viscosity of air into that of the liquid was totally proportional to the measured leakage rate of the liquid. Therefore, we concluded that the leakage rate of liquid can be estimated by measuring that of air.