Thermal-induced percolation in high-density polyethylene/carbon black composites

The networking of carbon black in high-density polyethylene melt has been traced by simultaneous electrical resistance (R) and dynamic storage modulus (G′) testing. Thermal-induced dynamic percolation was observed for both R and G′ as a function of annealing time. The influence of temperature and filler volume fraction on percolation times to R and G′ was investigated, and activation energies of dynamic percolation were determined. The percolation times were longer than the terminal relaxation time, and activation energies of dynamic percolation were significantly higher than those of viscous flow and molecular relaxation of the composites. A first order kinetics aggregation model was introduced into the classical percolation theory to account for the dynamic percolation. The contribution of filler networking was evaluated quantitatively.