DC and AC Conductivity of Carbon Nanotubes–Polyepoxy Composites

The dc and ac conductivities of carbon nanotubes-polyepoxy composites have been investigated from 20 to 110 °C in the frequency range 10-10 Hz as a function of the conductive weight fraction p ranging from 0.04 to 2.5 wt %. The frequency dependence of the measured conductivity obeys the universal dynamic response (UDR): a dc plateau followed, above a critical frequency ωc, by the ω power law with exponent s ∼ 0.6-1. The dc conductivity follows a percolation scaling law: σdc ∝ (p pc) with pc ) 0.3 wt % and t ) 1.4-1.8, according to the temperature. σdc reached 10 S/cm for 2.5 wt % CNTs content and increases with increasing temperature. Considering a biased random walk in three dimensions approach, we may explain the scaling law of ωc with p and its proportionality to σdc. The universality of ac conduction in carbon nanotubes-polymer composites is examined by the construction