The piezoresistive behaviors of polyethylene/foliated graphite nanocomposites

A conductive nanocomposite with an ordered conductive network and low-percolation threshold were prepared by adding foliated graphite (FG) nanosheets to high-density polyethylene (HDPE). The piezoresistive behavior of the nanocomposites was investigated under different pressure ranges. There existed a critical pressure below which composite resistance decrease with the increase of pressure and above which resistance increased sharply with increasing of pressure. The critical pressure is a function of the concentration of FG and the sensitivity of the change in resistivity against the applied pressure strongly depended on the FG content. The critical pressures of the nanocomposites with FG concentration at 6 vol.%, 11 vol.%, 12 vol.%, are about 7 MPa, 10 MPa, and 12 MPa, respectively. After repeated pressure treatment, there was a gradual decrease in the change of conducting structure although a permanent damage occurred due to the irreversible deformation of polymer matrix. As a result, the piezoresistive behavior of HDPE/FG nanocomposites tended to be constant under cyclic compression. The behavior was accounted for by an extension of tunneling conduction theory to which provides a good approximation to the piezoresistive effect.