Elucidation Of The Differences Between Thermal And Electrical Conductivity In
Polymer Composites Using Three Different Conductivity Models That Address
The Full Conductivity Range From Thermal To Electrical Conductivity

Richard D. Sudduth

Materials Research and Processing, LLC President and Chief Scientist, Peachtree Corners,
GA 30092, (UNITED STATES OF AMERICA)

PAGE NO: 026-054

ABSTRACT – DOI: https://dx.doi.org/10.47204/EMSR.7.1.2025.026-054

This study characterized of the transition from thermal conductivity to electrical conductivity in polymer composites using seven different data sets for the ratios of filler/matrix conductivity and using three different conductivity models. These three models included a modified Maxwell model, a modified Landauer model and the Sudduth Percolation Threshold (SPT) model that each have been shown to be capable of making the transition from thermal to electrical conductivity. In general, it has been found that the lowest filler/matrix conductivity ratios for thermal conductivity start with a linear relationship between Ln(composite conductivity) and concentration and change to S shaped curves that continues to increase in sharpness until electrical conductivity ratios are achieved. In addition, as the larger electrical conductivity ratios are approached the percolation threshold begins to shift to lower filler concentrations. Each of the models in this study also yielded a relatively simple equation to calculate the inflection points characteristic of the percolation threshold where the second derivative was goes to zero.

All of these models have been found to be capable of predicting a continuous scale of relative conductivity from thermal conductivity through to electrical conductivity. The Sudduth percolation threshold model was also found to be separable into both a conductive component and an insulating component which yielded a maximum conductivity based partially on the surface to volume ratio of the filler. Nevertheless, each of these different models did introduce slightly different characteristics involving the transfer from thermal to electrical conductivity in polymer composites.