Preparation and characterization of carbon fibre powder (CFP)-polyvinyl alcohol (PVA) composite films showing percolation threshold behaviour

Abstract

Carbon based polymer composites are important because of their probable electronic and biomedical applications. In the present work, we have prepared a composite of nano-size carbon fibre powder (CFP) with polyvinyl alcohol (PVA), hereafter referred to as CFP-PVA composite. Thin films of CFP-PVA composites have been prepared by solution casting method with different CFP concentrations (0.0–16 wt% or volume fraction f ∼ 0.0–9.15%). X-Ray diffraction (XRD) of the composites indicated enhanced crystallinity which influenced the electrical, dielectric, mechanical and thermal properties of the composite films. CFP filler concentration dependent conductivity and dielectric permittivity of the CFP-PVA composites showed interesting anomalous behaviour around a critical CFP concentration of 4 wt% (or fc ∼ 2.36% volume fraction). The observed anomalous behaviour indicated percolation threshold behaviour. Significantly high dielectric permittivity of the composite with low dissipation factor (tanδ varying from ∼ 0.1–0.5, for different concentrations, at a fixed frequency of 1 kHz) was considered to be due to the formation of micro capacitors in the composite and charge ordering within these micro-capacitors, near the percolation threshold. Improved electrical conductivity, dielectric permittivity, mechanical and other properties indicated multifunctional behaviour of the conducting CFP-PVA composites. The probable electronic and other applications of the composites have also been discussed.