The effect of natural tropical climate to the surface properties of silicone rubber

The surface of polymeric insulators, when they are new, are generally extremely water repellent, with great advantages in terms of dielectric strength. This characteristic is not usually maintained during service, especially if the insulators are operated in a severe tropical environment. This paper reports the influences of natural tropical climate in Bandung, Indonesia on the surface properties of the HTV and RTV silicone rubber with different filler contents. Samples of HTV and RTV silicone rubber with different filler contents were installed in an open-air plane for natural tropical climate aging. To determine the effect of UV radiation, some of the samples are protected from natural UV by a shield. The changes of the surface hydrophobicity were monitored periodically by using static contact angle measurement and scanning electron microscopy (SEM). The results of measurement over 52 weeks indicated that the natural tropical climate did not affect the surface hydrophobicity of silicone rubber significantly. Moreover the samples exposed without shielding showed more hydrophobicity (contact angle ≈145°) than the samples exposed with shielding (contact angle ≈127°). The hydrophobicity transfer aspects for a natural pollutant on the surface are discussed