Silicone Rubber Composites with High Breakdown Strength and Low Dielectric Loss Based on Polydopamine Coated Mica.

High breakdown strength and low dielectric loss are necessary for the outdoor insulator using silicone rubber (SR) composites. In this work, polydopamine coated mica (mica-PDA) was synthesized via bioinspired dopamine self-polymerization, and mica-PDA-filled SR composite (SR/mica-PDA-VTMS) was prepared using vinyl tri-methoxysilane (VTMS) as a silane coupling agent which serves as the molecular bridges between the organic rubber and the inorganic filler. The SR/mica-PDA-VTMS composite demonstrated dense and uniform morphology where the filler was well dispersed. Due to the strong interfacial interactions between filler and rubber, the SR/mica-PDA-VTMS composite exhibits much lower dielectric loss compared to the other mica-filled SR composites, which was comparable to the prepared alumina-tri-hydrate-filled SR composites. Moreover, the breakdown strength of ~31.7 kV/mm and tensile strength of 5.4 MPa were achieved for the SR/mica-PDA-VTMS composite, much higher than those of the other as-prepared SR composites.