Molecular Dynamics Simulation on Water Diffusion into HTV Silicone Rubber used in High Voltage Composite Insulator

Water diffusion and permeation are considered the major mechanism for describing the aging phenomena of high temperature vulcanizing silicone rubber used in outdoor high voltage composite insulator. In order to obtain an appropriate model to investigate the water molecule diffusion process into silicone rubber, as well as the diffusion characteristics of this process, molecular dynamics simulation method was employed to study the water diffusion process into HTV silicone rubber. The simulation results revealed that the ATH filler in the silicone rubber composites was the main waterabsorbing component in comparison with the silica filler. The elimination of surface hydroxyl groups on the silica filler surface can improve the hydrophobicity of the composites and therefore can contribute to reducing the amount of moisture absorbed in the composite. In actual HTV silicone rubber, the surface hydroxylation degree of silica was low, and PDMS would be wrapped on the silica surface, so silica should have less influence on the water absorption of the system than that of ATH filler. The present study is helpful for better understanding of water diffusion into HTV silicone rubber and into other composite containing different kind of filler used in electrical engineering.