Synergistic Aging of Silicone Rubber by Wet/Dry Heat and Silicone Grease

The interface of cable joints formed by cross-linked polyethylene (XLPE) and silicone rubber (SR) are not only affected by the temperature, but also by moisture and silicone grease (SG). In this paper, the synergies effects of moisture, heat and SG on the insulating properties of SR in cable joint is investigated. The aging experiment of SR were carried out. Molecular dynamics simulation was carried out to study the influence mechanism of SG, temperature and humidity on the structure of SR. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy were used to study the microstructure of the materials. XPS shows that SG reduces the free volume of SR and provides more cross-linking sites, which promotes the oxidative cross-linking reactions on the surface of SR at high temperatures. Therefore, the hardened inorganic layer appears on the surface of the specimen. What's more, the Raman spectroscopy result shows that the high temperature promotes the swelling caused by SG, which destroys the internal cross-linking network of the specimen and breaks the polymer chains. The mechanism of internal and surface deterioration of SR are different, but SG and dry/humid heat environment play a joint role in the aging of SR.