Evaluation Method of Hydrophobicity Degradation of Silicone Rubber without Alumina Trihydrate

Silicone rubber (SiR) of housing material of electric power apparatus is degraded owing to environmental stress. If the degradation of SiR can be measured, the long-term maintenance of the electric power apparatus may become possible. We focused on hydrophobic recovery of SiR which is superior to other housing materials, and the degradation of hydrophobic recovery of SiR without alumina tri-hydrate was evaluated. The hydrophobic recovery time was measured after the surface discharge (SD) was generated on the SiR surface. It was found that the hydrophobic recovery times of SiR specimens aged 15 years were longer than that of unused SiR. This indicates that the SD method can measure the degradation of SiR.