Test MethodComparison of electrical conductivity data obtained by four-electrode and four-point probe methods for graphite-based polymer composites

A comparison of the volume conductivity measured by standard four-electrode (FE) and four-point probe (FPP) methods for graphite-based powdery polypropylene (PP) and poly(vinylidene fluoride) (PVDF) composite bar specimens was made in this study. Significant difference in the conductivity data obtained by standard FE and FPP methods was found for highly conductive PP and PVDF composites which were molded from hybrid carbon/polymer powders dry-blended in a high-speed mixer and jar ball mill. However, it was found that the conductivity values were approximately equal for moderately conductive PVDF/graphite and PP/graphite composites. It was also shown that polishing the specimens to remove 100-150 μm of the surface layer and decrease surface roughness did not bring about significant changes in conductivity values. Consequently, bulk non-uniformity and inhomogeneity of graphite-based polymer material were considered to be the most probable sources of the difference in the volume conductivity values measured by the FE and FPP methods.