Effects of Hygrothermal Conditions on Corona Aging of Silicone Rubber

Abstract

In this research, high-temperature vulcanized silicone rubber is used as a sample to conduct a hygrothermal corona aging test. The physicochemical and electrical performance of the silicone rubber are tested under different hygrothermal conditions. The results show that the surface structure of the material is increasingly destroyed and even pulverized as humidity or temperature rises. Compared with the original samples, the static contact angle of the aged samples decreases significantly, and the static contact angle of the aged samples that exhibit pulverization expands compared with those unpulverized samples due to the large amount of small-molecule siloxanes contained in the pulverized layer. The main chain and side chain of the aged silicone rubber are damaged to varying degrees. The absorption peaks of Si–O–Si and Si–CH3 bonds in the aged samples that exhibit pulverization are higher than those of the samples that do not exhibit pulverization since the siloxane also contains Si–O–Si and Si–CH3 bonds. The aged material combines with a large number of polar groups, leading to an enhanced polarity of the silicone rubber molecules and more dielectric loss of the material. The surface resistivity and volume resistivity of the aged samples are 6.5% and 70.3% of those of the original samples at 80 °C and 95%, respectively, showing that corona discharge mainly damages the surface, rather than the interior of the material.