Aggregate structure and percolation behavior in polymer/carbon black conductive composites

The percolation behavior and mechanisms of electrical conductivity in carbon black filled polymer composites were analyzed. An aggregate structure model of the carbon black particles was proposed based on the effective media theory (EMT) and the equivalent sphere of carbon black aggregate acts as a basic cell to describe the nonlinear conductive behavior. Then, a formula describing the relationship between the conductivity and the volume fraction of carbon black particles as well as an expression estimating percolation threshold of the composites were derived. This aggregate structure model overcomes the disadvantage of the EMT which cannot explain the phenomenon that percolation threshold is lower than 1/3. Based on these expressions, the electrical conductivity and percolation threshold of several kinds of conductive polymeric composites were predicted and the results showed that the predictions were preferably consistent with the experimental data from the references. (C) 2007 American Institute of Physics.