Enhanced nonlinear conductivity of silicone rubber composites with hybrid graphene and alumina for cable accessory

The electric field distortion and charge accumulation in cable accessories are still challenges for high voltage direct current transmission (HVDC). Using silicone rubber (SR) based materials with nonlinear conductivity properties can ameliorate these problems in cable accessories. Herein, SR composites with hybrid filler network were prepared by adding graphene (G; 0.25 phr) and alumina particles (Al2O3; 5–40 phr) to SR to obtain good nonlinear conductivity and relative high breakdown strength, along with thermal conductivity. The SEM results showed that graphene was well dispersed between Al2O3 particles and a hybrid filler network was constructed in the SR matrix. The G/Al2O3/SR composites exhibited favorable nonlinear electrical conductivity properties and thermal conductivity properties while sustaining high breakdown strength under different electrical and temperature field. The non-linear conductivity α of the 0.25G/40Al2O3/SR composite reached 6.68 at 23 °C, whereas the breakdown field strength E0 of 49.1 kV/mm could comparable to that of pure SR. Moreover, the thermal conductivity of 0.25G/30Al2O3/SR was 0.28 Wm−1K−1 at 23 °C, which increased by 114.98% compared to pure SR. This work suggests the promising application of G/Al2O3/SR composites as cable accessory. •A small amount of graphene combined with different amounts of Al2O3 were used to form a hybrid filler network in the SR matrix.•The G/Al2O3/SR composites have good nonlinear conductivity.•The thermal conductivity of the SR composites was improved.