Properties of silicone rubber housings and coatings

The author reports on the properties of a silicone rubber (SR) composite insulator housing material and a RTV silicone coating for porcelain insulators after a surface deposition of salt pollutants. The materials had undergone long-term aging under natural service conditions. It was found that a wettability recovery effect could appear after a corona treatment on the SR housing material, but this did not occur in the case of the RTV coating. The difference is probably due to the fact that the SR housing, even after exposure to a long-term service, can still embed pollutants in a low molecular polymer structure, whereas the RTV coating loses this ability when subjected to the same aging conditions. This is confirmed by ESCA analysis. The materials were also investigated by means of TSD current technique. Significant changes due to natural aging were found in the thermokinetic parameters of a high-temperature polarization process. It is suggested that these parameters might be used for material comparison