Surface renewal mechanism during laser-cleaning of aged silicone rubber composites

Abstract

Silicone rubber composite insulators are an important component of the power grid, but prolonged use can cause surface aging and decrease hydrophobicity, leading to safety hazards. Removing aged silicone rubber can improve hydrophobicity and extend service time, but there is no suitable means to achieve these objectives due to the high safety requirements of transmission lines. Therefore, we researched laser cleaning technology to remove aged silicone rubber to restore hydrophobicity. The effect of removal depth and microscopic morphology under defocusing and spot overlap were investigated. It was found that silicone rubber was mainly removed by decomposition when the defocusing was less than 20 mm, while combustion removal occurred when the defocusing was more than 30 mm. The spherical, massive and irregular particles were produced by the decomposition mechanism, while products with porous structure were generated by combustion. Both decomposition and combustion could effectively improve the hydrophobicity of aged composite insulators. The maximum contact angle could be increased from 75° to about 140°, but combustion increased the surface roughness from Ra 1.78 μm to a maximum of Ra 6 μm, while the maximum roughness is only Ra 3 μm with decomposition. The Shore A hardness of the laser-treated samples remained relatively stable, ranging from 76 HA to 80 HA.