Variation of the general mixing rule to explore the interphase in the AC electrical conductivity of polypropylene melt-mixed with as-grown carbon nanofiber composites

A variation of the phenomenological mixing rule model is used to study the AC electrical conductivity of melt-extruded polypropylene (PP) compounds with varying carbon nanofibre (CNF) contents (0 to 1.4 vol. %). The results show an insulator-conductor transition at 0.9 vol. % CNF content, where the conductivity reaches ∼ 4 × 10 -8 S m -1 at 430 Hz, while at the highest CNF loading of 1.4 vol. % increases up to ∼ 6 × 10 -6 S m -1 , which makes them suitable as electrostatic dissipative (ESD) materials. From the modified mixing rule model, it is shown that the electrical conductivity ( σ int ) and the volume constant ( k ), associated with the interphase, increase and decrease with the frequency, respectively, while the volume concentration of the interphase ( ϕ int ), despite increasing linearly with increasing vol. % of CNFs, decreases as frequencies increase, demonstrating that its effect becomes smaller as the frequency increases.