RELATIONSHIP BETWEEN UNIAXIAL DEFORMATION AND PIEZORESISTANCE FOR HDPE/CB COMPOSITES

Abstract

The mechanism of piezoresistive behavior and the improvement of its stability for high-density polyethylene/carbon black(HDPE/CB) composites were studied.The results revealed that the uniaxial piezoresistive behavior resulted from the change in the structure of the percolation network,depending on the filler volume fraction φ and the deformation of the material under pressure.When φ approached the percolation threshold φ_c,with increasing external pressure the composites exhibited a positive pressure coefficient(PPC) effect for its resistance.In the case of φ far beyond the φ_c,only a negative pressure coefficient(NPC) effect for its resistance can be observed.The resistance baseline at zero pressure after unloading shifted upward or downward with the increase of the numbers of compressive cycles,depending on the φ.The shift of the baseline was related with the residual compressive strain and can be stabilized by increasing the number of the compressive cycles.Crosslinking of the matrix can restrict the residual compressive strain and stabilize the baseline shift of the resistance-time curve,especially for the composites with a high φ.