The uniaxial piezoresistive characteristics for graphite powder filled high density polyethylene (HDPE/GP) conductive composites are studied. The results show that there exists a marking pressure dependence of the conductivity in HDPE/GP composites, in which the so-called negative pressure coefficient of resistive (NPCR) and positive pressure coefficient of resistive (PPCR) are observed under minute and moderate pressures. Under constant pressures, time-dependent resistivity is an outstanding characteristic for the composites, which is defined as resistance creep. The breakdown and rebuild-up process of conductive network under pressure may be responsible for the pressure- and time-dependence of resistivity.
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