Hydrophobicity of silicone rubber used for outdoor insulation

The objectives of this study on silicone rubber materials were: (1) to determine the threshold of low molecular weight (LMW) silicone polymer on the surface needed for hydrophobicity recovery, after it has been temporarily lost due to dry band arcing, and (2) to determine the dominant source of LMW chain regeneration after the initial supply has been depleted. The samples were obtained from new and artificially aged high voltage composite insulators using HTV silicone rubbers for weathersheds, and ceramic insulators using RTV silicone rubbers as a protective coating. The experimental techniques used were Crossover Voltage (COV), Energy Dispersive X-Ray Spectroscopy (EDX), and X-Ray Mapping (XRM), all performed in a Scanning Electron Microscope (SEM). The results indicate that only a small fraction (10% to 20%) of the LMW polymer content present on an unaged material surface is needed for hydrophobicity recovery. The trend in the results was consistent for the different compositions of HTV and RTV silicone rubber materials evaluated