Evaluation of Degradation Degree on Silicone Rubber by Using Surface Discharge

Silicone rubber (SiR) insulators in outdoor may be degraded owing to multiple environmental stresses such as ultraviolet (UV) rays, high temperature and pollution adhesion. Evaluation of the degradation degree of SiR can contribute to the long-term maintenance of SiR insulators. We proposed a novel technique to grasp the degradation degree of SiR. The surface discharge (SD) on the SiR surface temporarily decreased the surface hydrophobicity, and then the hydrophobicity recovery time was evaluated. The SD treatments were performed on SiR specimens cut out from unused, 10 and 20-year-aged SiR insulators, and the treatment time was from 5 to 25 s. After each SD treatment, the contact angle was evaluated at intervals of 10 min. As a result, it was found that the contact angle recovery time increases with the increase of SD treatment time. Also, the contact angle recovery times on 10 and 20-year-aged SiR specimens were longer than that on an unused SiR specimen, i.e. the contact angle recovery time after the SD treatment is useful for investigating the degradation degree. © 2025 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.