Micro Structural and Electrical properties of Liquid Silicone Rubber Used for External Insulation

Abstract

In recent years, liquid silicone rubber (LSR) has been widely used in the external insulation field due to their excellent insulation properties and mechanical performance. LSR is a kind of addition silicon rubber, which has no by-products with vulcanization process and has very low line shrinkage. In this work, LSR based composites filled with boron nitride (BN) particles were prepared by mechanical blending. The surface of BN was functionalized with a coupling agent to increase the compatibility of BN and LSR. The scanning electron microscopy (SEM) was used to characterized the morphologies of the LSR composites, and their electrical properties were also studied. From the SEM images, there are no obvious interfaces between BN and LSR. The breakdown strength of the LSR composites is higher than that of pure LSR. When the content of BN is 40 wt%, the breakdown strength of LSR composite is 45 kv/mm. The outstanding insulation performance of the LSR composites were ascribed to the good dispersion of BN. The highest value of thermal conductivity was obtained for the LSR composite containing 40 wt% BN, and the thermal conductivity is 0.96 $\mathrm{W}\cdot \mathrm{m}^{-} 1\mathrm{K}^{-1}$. Compared to 0.18 $\mathrm{W}\cdot \mathrm{m}^{-1}\cdot \mathrm{K}^{-1}$ of pure LSR, which means a 557% increment. The LSR composite with high thermal conductivity and good insulation properties was very important for electrical power engineering.