Effect of micro-Si3N4-nano-Al2O,sub>3 co-filled particles on thermal conductivity, dielectric and mechanical properties of silicone rubber composites

Silicone rubber (SR) is widely used on the distribution and transmission lines of power systems owing to its excellent insulating properties, extraordinary hydrophobicity and high tensile strength. However, the thermal conductivity of pure silicone rubber is very low which restricts its application for long time due to heat formation under electric field. This research focuses on the effect of micro-and nano-sized filler mixture on thermal conductivity, dielectric and mechanical properties of the SR composites. The micro-Si₃N₄ and nano-Al₂O₃ cofilled SR composites (MNCSR) with different volume ratios of Si₃N₄ and Al₂O₃ were fabricated by simple blending and subsequently hot molding technique. With the addition of micro-Si₃N₄-nano-Al₂O₃ mixture at 30 vol. % (Si₃N₄/Al₂O₃=26/4), the composites showed high thermal conductivity of ~ 1.6 W m^-1 k^-1, low relative dielectric permittivity of ~ 5.3 and high breakdown strength of ~ 85 MV/m. Meanwhile, the introduction of micro-nano-sized particles resulted in improved elongation at beak and tensile strength. Besides, the MNCSR composites demonstrated good hydrophobicity with the static contact angle over 110°. The combination of these outstanding performances makes the MNCSR composites attractive in the field of insulating materials.