Nonlinear conductive behaviors of multilayer graphene nanosheets/epoxy composites below the percolation threshold

The development of nanotechnology is of crucial importance in advanced polymer nanocomposites with enhanced properties. Here, multilayer graphene nanosheets/epoxy composites with various filler contents were fabricated by solution blended processes. It was found that the incorporation of graphene nanosheets increased the real part of permittivity and dielectric loss tangent. The thermal conductivity had a certain effect by the incorporation of 0.1 wt.% and 0.5 wt.% graphene nanosheets, which increased by 3.87% and 31.95% at 100 °C. Moreover, the polarization current of neat epoxy composite and graphene nanosheets/epoxy composites were measured under different applied electric field and at 50 °C, 80 °C and 100 °C. The conductive mechanism of the composites transformed from Ohmic conduction to Space Charge Limited Current (SCLC) conduction at a threshold of conductive current electric field (E _thi ), Ethi decreased with increasing temperature and graphene filler content. The conductive mechanisms of graphene nanosheets/epoxy composites under high electric field are influenced by both SCLC and tunneling effect.