Effect of filler blend composition on the electrical and mechanical properties of conductive EVA composites

The electrical conductivity and mechanical properties of ethylene vinyl ace tate based polymeric composites filled with short carbon fibres (SCF) and c onductive carbon black has been investigated. While carbon fibres provide c harge transport over large distances, carbon black improves inter fibre con tact and mechanical properties by reinforcing the polymer matrix. The resis tivity 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, lead ing to the phenomena of electrical hysteresis and electrical set. These com posites show both NCT (negative coefficient of temperature) and PCT (positi ve 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 electro n emission theory.