Ultraviolet Weathering Resistance Performance of Micro/Nano Silica Filled Silicone Rubber Composites for Outdoor Insulation

The degradation of high voltage (HV) outdoor polymeric insulators due to ultraviolet (UV) weathering environment has long been remaining a research subject for the reliable power delivery. Such weathering conditions produce chemical changes on the surface of insulators and significantly impact on the hydrophobicity, roughness and surface structure. This paper describes the experimental findings on the accelerated UV weathering resistance of micro and/or nano silica filled silicone rubber (SR). Four different types of composite are synthesized: unfilled (U-SR), micro-silica filled (M-SR), nano-silica filled (N-SR) and micro/nano silica mixture (MN-SR). All the composites are exposed to the synergetic effect of UV, elevated temperature and AC electric stress in a chamber for 104 days. Experimental findings indicate that N-SR significantly resists the drop in hydrophobicity. Also, considerable gain in the surface roughness of composites is observed at the end of weathering relative to the virgin state. A sharp gain in the average and peak surface roughness of M-SR and MN-SR is measured, respectively. Significant silica particle exposure is noticed in M-SR and MN-SR but a very smooth surface of N-SR is captured in the SEM results. Few surface crackles are noticed on the surface of M-SR and N-SR. From the above results, it can be concluded that nano-sized silica particles in N-SR compose a better UV reflecting layer which makes it superior over the other composites.