Improvement of electronic properties of Ni/PVDF composite films by stretching

In order to further understand the stretching effect of polymer-based composites，the Ni/PVDF films were prepared using a simple physics blending and then stretched at 120℃ to improve the electronic properties. The results show that there is an abrupt increase of 17 times (12→220) in the dielectric constant of the stretched samples at the stretching ratio of 2.3 with Ni content less than the percolation threshold，which is similar to percolation and named stretching-induced percolation. Additionally，an insulation-conduction transition tends to occur with enhancement of 4～5 orders of magnitude in conductivity after stretching. The enhancement in the dielectric constant with increase of stretching ratio is attributed to the gradual formation of conductive networks induced by stretching，which consists of a great many nickel groups and micro-parallel-capacitors. The large increase in conductivity is in agreement with the percolation theory before and after stretching.