Contents 1 Introduction
SILICONE rubber, as the important material of composite insulator, has been widely used in power network system [1], for that it has excellent hydrophobicity and hydrophobicity transfer property, which prevents formation of continuous films of water on the surface of contaminated composite insulators. When composite insulators, operating in highly polluted environment, were eventually covered by a layer of contamination, hydrophobic property of the silicone rubber could ‘transfer’ to the surface of pollution layer [2] [3], whereby hydrophilic pollutants on the surface would gradually become hydrophobic. Most of studies agreed that this hydrophobicity transfer mechanism came from low molecular weight (LMW) silane chains in the bulk of silicone rubber migrating to the surface and becoming physically or chemically adsorbed by the non-soluble materials in the pollution layer. The non-soluble pollutants then themselves become hydrophobic and surround the soluble salts in the layer. The whole pollution layer has, at the end, also become hydrophobic. Thus composite insulators have superior pollution withstand performance and higher pollution flashover voltage than glass and porcelain insulators.
