Electrical properties of polymer/expanded graphite nanocomposites with low percolation.

Expanded graphite (EG)-filled poly(phenylene sulfide) (PPS) nanocomposites prepared by a simple method exhibited an electrical conductivity percolation threshold of 1 wt% (0.6 vol%). In contrast to this, the percolation threshold of micrometre-sized graphite flake filled PPS composites prepared by the same method was 5 wt%. The electrical conductivity for 2 wt% nanocomposites increased 14 orders of magnitude higher than that of pure PPS. The dielectric constants and dissipation factor of nanocomposites were measured in a frequency range from 100 kHz to 15 MHz. The dielectric constant of the nanocomposites with more than 1 wt% EG showed a strong dependence on EG content and frequencies. The dielectric constants for 2 wt% and 10 wt% nanocomposites measured at 1 MHz were increased more than 102 and 105 times, respectively. Similarly, the dissipation factor was increased. Scanning electron microscopy showed a three-dimensional conducting network of EG across the PPS matrix which may be the reason for the significant improvement in electrical properties. The significantly increased electrical conductivity, dielectric constant and dissipation factor of the nanocomposites are favourable for their use in antistatic and electromagnetic interference shielding applications. [ABSTRACT FROM AUTHOR]