Study On Thermal-oxidative Aging And Life Assessment Of Rubber Sealing Material

Rubber seals are polymer materials which are widely used in aerospace, chemical, electrical and electronics, medical equipment and mechanical manufacture and other fields. Their properties will reduce progressively under the environmental conditions of high temperature, oxygen, and mechanical stress etc, that is so-called "aging". At present, a lot of research work at home and abroad about micro-chemical changes of the rubber thermal oxidative aging has been carried out , but few people have discussed the aging failure mechanisms by the combination of micro-morphology and the mechanical properties. So far, the domestic and international studies about aging lifetime prediction of rubber seals are at an early stage of theoretical study.Static load thermal oxidation accelerated aging tests are carried out under the conditions of 5 temperatures based on butadiene rubber material, and from the mechanical properties, microstructure morphology and element content, the butadiene rubber failure mechanisms of aging is researched. It is found that butadiene vulcanizate contains residual unvulcanized component, so the aging process is accompanied by cross-linking and breaking reaction of the chain. For the early aging, breaking reaction occurs mainly, for the late aging, cross-linking reaction dominate. At the same time, it is also found that due to diffusion-limited oxidation, internal and external performance of butadiene rubber materials are very different. Therefore finite element simulation under the compression have been conducted. The results show that the aged butadiene rubber properties are very different inside and outside , for inside and outside of the materials, the uniform constitutive model is set up, using the simulation data can not simulate the yield phenomenon appeared in the compression test, in turn, it has proved that after aging the constitutive relations between internal and external butadiene rubber have been changed.The data of the changing of compression set with time under different temperatures are determined, for 298K, the proportion of residual performance is 30%, according to the national standard, it is predicted that rubber seal material storage lifetime is 20.25 years; while rate constant K values are calculated under the degradation of 5 temperature points by kinetic formulas. Arrhenius diagram stablished, it is found that the non-Arrhenius behavior, and on this basis, the rubber seal material storage lifetime prediction model is established and the activation energy is the characterization parameter. The stored lifetime of studied rubber seal materials are predicted. the results show that under the same conditions the predicted result is 7.01 years; compared with the actual storage lifetime of 3-5 years ,it can be shown that the model established in this study and forecasting methods are more accurate.