Understanding the impact of different nanofillers on electrical, thermal, and surface properties of corona-aged silicone rubber nanocomposites

In the present work, the impact of corona aging on the dielectric, thermal, and surface properties of silicone rubber filled with different nanofillers such as alumina (Al2O3), aluminum trihydrate (ATH), boron nitride (BN), and titania (TiO2) are studied. The surface degradation of the silicone rubber nanocomposites after corona aging is evaluated through contact angle measurement, atomic force microscopy (AFM) studies, and by water droplet-initiated corona inception voltage studies. Alumina filled silicone rubber shows less reduction in surface and hydrophobic properties after corona aging. Water droplet initiated corona inception voltage (CIV) under negative DC voltage is much higher than under positive DC and AC voltages. Al2O3/TiO2- filled silicone rubber samples show better CIV performance. The Dielectric Response Spectroscopy (DRS) indicates that TiO2 filled silicone rubber insulating material possesses higher permittivity at lower frequencies. Boron nitride added composites have high thermal conductivity whereas ATH filled silicone rubber composites shows higher decay rate, as observed through laser-induced thermography studies. A significantly high surface leakage current is observed in all samples after corona aging. The Space Charge Limited Current (SCLC) studies clearly indicate that inclusion of nano-fillers resulted in an increase in crossover voltage and trap density values compared to base silicone rubber.