Influence of surface roughness on hydrophobic stability of silicone rubber composites in dynamic drop test

Hydrophobic stability of silicone rubber composites is considered to be important for long-term insulating performance of polymeric outdoor insulator. Recently, dynamic drop test (DDT), which could evaluate the stability of hydrophobicity under ac voltage application, has been developed as a standard laboratory test in the CIGRE. This paper presents an attempt to derive the influence of surface roughness to the hydrophobic stability of silicone rubber composites with using DDT. Experiments were carried out with the silicone rubber composites, whose surface was scratched in vertical and horizontal directions by sandpapers. As the result, we verified that the time to loss of hydrophobicity (T_loss) was decreased by increasing the surface roughness. Furthermore, the surface roughness effect on T_loss was discussed with the measurement results of the static and dynamic contact angle.