Effect of Filler Blend Composition on the Electrical and Mechanical Properties of Conductive EVA Composites

The electrical conductivity and mechanical properties of ethylene vinyl acetate based polymeric composites filled with short carbon fibres (SCF) and conductive carbon black has been investigated. While carbon fibres provide charge transport over large distances, carbon black improves inter fibre contact and mechanical properties by reinforcing the polymer matrix. The resistivity of the composites decreases with increasing SCF concentration in the filler blend, but the mechanical properties decrease. The change in volume resistivity during heating and cooling does not follow the same path, leading to the phenomena of electrical hysteresis and electrical set. These composites show both NCT (negative coefficient of temperature) and PCT (positive coefficient of temperature) depending upon the filler blend ratio in the polymer matrix. This observation of temperature dependence is explained by both the differential thermal expansion of polymer and Filler, and electron emission theory.