Erosion resistance of micro-AlN and nano-SiO₂ hybrid filled silicone rubber composites

Erosion of weathershed composite materials is one of the key failure modes in outdoor insulators and it can adversely impact on the reliability of power system networks. To enhance resistance against erosion and dry band arcing, inorganic particles are often added to base polymeric matrix. This paper investigates the erosion resistance of micron-AlN and hybrid micron-AlN + nano-silica filled silicone rubber composites. Micron aluminum nitride (AlN: 5-10 μm) and nano-silica (SiO₂: 20 nm) particles were obtained for fabrication of composites. Five samples for each type were tested by following the inclined plane test (IPT) procedure as described in IEC 60587. The step wise tracking voltage (method 2) was adopted for the IPT with initial voltage of 3 kV, ramping rate of 250 V/h and duration of 4 h. Results show that hybrid composites exhibit substantially lower eroded mass than micron-AlN filled composites. Moreover, the average leakage current in hybrid composites is noticeably lower than 30%m-AlN. Hence, it is expected that this may help restrict dry band arcing and thermal induced erosion degradation. Morphological results show that a pit appeared in 30%m-AlN with large depth and extensive cracks inside. Only minor erosion depth is noticed in 28%m-AlN+2%n-silica with compact structure on the edges of eroded region. Better thermal stability and thermal conduction ability can be possible reasons for the better performance of hybrid filled composites in IPT.