Accelerated weatherability of shed materials for composite insulators

Shed materials for hollow composite insulators (low temperature vulcanized silicone rubber, high temperature vulcanized silicone rubber, ethylene vinyl acetate and ethylene propylene diene monomer) were examined through accelerated weathering tests and their weathering resistances were evaluated from changes of surface and bulk properties. For silicone rubber, changes in the content of low molecular weight silicone (silicone oil) related to maintaining water repellency were investigated. The results showed that silicone rubbers had excellent weathering resistance and kept high water repellency during long term weathering tests. Using an equivalent model, an investigation was also carried out on how non-soluble contaminations deposited on the surfaces of sheds in outdoor service could cut off UV rays.