Enhanced positive temperature coefficient effect by crosslinking reaction for silicone rubber/carbon black composites with high pressure sensitivity

Abstract Positive temperature coefficient (PTC) composites are usually made of crystalline plastics and conductive fillers, but they are not suitable for flexible electronic devices because of their high rigidity. Rubber‐based PTC composites are flexible but their PTC intensity is low. In this work, based on the effect of crosslinking reaction on the electrical conductivity of silicone rubber composites, silicone rubber/conductive carbon black composites with an obvious PTC effect were prepared. Compared with the hydrosilylation crosslinking reaction, the peroxide crosslinking reaction has much more obvious decrease in electrical conductivity of the composites. The conductive percolation threshold of the composites was 4.98%. A composite filled with 5.98% conductive carbon black showed obvious PTC effect at circa 150°C, which can be attributed to the re‐aggregation of conductive carbon black in silicone rubber during the crosslinking process. The composite with an obvious PTC effect was well used in an overheating protection device. The composite exhibited an excellent pressure‐sensitivity of conductivity.