Reduced percolation thresholds of immiscible conductive blends of poly(ethylene-co-vinyl acetate) and high density polyethylene

The electrical response of polymer composites employing a “percolation-within-percolation” approach of carbon black reduction required for imparting conductivity to the composites was investigated. Specifically, immiscible polymer composites composed of poly(ethylene-co-vinyl acetate) (EVA), high density polyethylene (HDPE) and carbon black (CB) were investigated. The ternary composites exhibited enhanced conductivities above that of the individually filled binary polymers at equivalent carbon black concentrations. Significant increases in the conductivity of (semi)conductive composites could be achieved through annealing at temperatures below the melting point of the HDPE, with compositions containing carbon black levels close to the percolation concentration experiencing the greatest benefit. Optical analysis of the annealed composites indicated a coarsening of the blend morphology which was speculated to be assisting in improving the conductivity of the composites. The ternary composites exhibited an upward shift in relative permittivity values with increasing HDPE/CB content through the enhanced Maxwell-Wagner interfacial polarization taking place between the three dissimilar components