Preparation and performance of graphene/carbon black silicone rubber composites used for highly sensitive and flexible strain sensors

[Display omitted] •The free radical polymerization of MPS is used to improve the CCB dispersibility in SR.•The SR/graphene/CCB composite shows high stretchability and deformation recovery properties.•The SR/graphene/CCB composite has very high strain sensitivity and good durability.•A strain sensor prepared by the composite can detect the pulse beating processes. Flexible strain sensor plays an increasingly important role in wearable electronics industry. How to prepare flexible strain sensors with high stretchability and excellent strain sensitivity at different strains is a big challenge. In this work, the free radical polymerization of a silane coupling agent was initiated on the surface of conductive carbon black (CCB) to improve its dispersibility in silicone rubber (SR). The resultant modified CCB and graphene with different ratios were filled in SR to prepare SR/graphene/CCB composites. A composite with 4 phr graphene and 2 phr modified CCB has the maximum strain of 123 % and good deformation recovery. The composite has high strain sensitivity with the gauge factor of 326 and 1.89 × 104 at the strain ranges of 8 %–10 % and 28 %–44 %, respectively. Besides, a strain sensor based on the composite shows good durability over 1000 cycles. It can detect the human motions such as pulse beating, swallowing and muscle contraction processes. Flexible strain sensors made of SR/graphene/modified CCB composites have a great application potential in the wearable electronic devices field.