Percolation conductivity of polymer composites filled with dispersed conductive filler

Abstract This paper deals with the conductivity of binary polymer composites filled with an electronically conductive material. A “dynamic cluster model” is offered to describe the conductivity of such polymer composites in the highly filled region, i.e. above the percolation threshold. The model is based on the following assumptions: a modification of the basic statistical percolation equation, i.e. σ (φ−φ c ) t , where t = 1.6 to 1.9, should be applied for all systems in the highly filled region, although application is limited to the range φ = φ c + Δφ, Δφ ⟹ 0 in the strict statistical percolation approach; the most important modifications with respect to the basic equation of the statistical percolation theory are (a) the use of a constant t eff , including a constant part t 1 (resembling “ t ” in the basic statistical percolation approach) and a variable part t 2 (depending on the filler concentration φ of the specific mixture) and (b) the definition of φ c as the filler concentration where a perfect three‐dimensional network of the conductive phase has been established. This idea has been adopted from the bond‐percolation approach of Aharoni; the resulting equation should include parameters of specific polymer composites. The generalized equation σ = f (φ) is used to calculate the maximum possible conductivity of a certain mixture as well as the dependence of σ on the filler content.