Comparison of ATH and SiO2 fillers filled silicone rubber composites for HTV insulators

Abstract To enhance the electrical and mechanical properties of silicone rubber (SIR) in the field of high-voltage insulation, conventional fillers such as aluminum hydroxide (ATH), fumed silica and precipitated silica have been used for many years. In this work, SIR composites filled with ATH, irregular SiO 2 (IS) and sphere SiO 2 (SS) were prepared by mechanical blending, and the effects of filler type and filler shape on mechanical, electrical and thermal properties of SIR composites were systematically investigated. Compared with ATH-SIR composites, SS-SIR composite exhibited better electrical and mechanical properties. It showed that the tensile strength of SS-SIR composites was up to 6.6 MPa, which was nearly 2-folded compared to ATH-SIR composite. According to the loss tangent results in combination with tensile fracture surface observation, the interfacial interaction between SiO 2 fillers and SIR is stronger than that between ATH and SIR, and the dispersion is better in SiO 2 fillers filled SIR composites than that in ATH filled composite. The breakdown strength of ATH-SIR composite is only 18.9 kV mm −1 , while those of IS-SIR and SS-SIR composites are 24.9 and 24.8 kV mm −1 , respectively. Among the three SIR composites, SS-SIR composite has lowest dielectric permittivity and dielectric loss. Compared with ATH-SIR composite, the SiO 2 fillers filled SIR composites have the lower thermal conductivity ranging from 30 °C to 150 °C, but they exhibit the better arc aging resistance due to the good thermal stability and thermal conducting property at high temperature. Moreover, the SS-SIR composite exhibits the better arc aging resistance than IS-SIR composite.