DC conduction mechanisms in epoxy nanocomposites under the humid environment

In this paper, time dependent direct current conduction characteristics were studied for both micro- and nano-filled epoxy composites at 0% and 75% relative humidity with temperature range of 298K to 343K. At low loading content of nanofillers, composites had similar conduction mechanisms as the matrix, which were ohmic conduction at low field or trap-filled limit conduction dominated at higher field. However, the higher concentrations of inorganic filler would shift the conduction mechanism to Schottky emission at higher field. Once the buildup of space charge was completed in composites, the quasi-steady state current deviated from the low-field linear relation with electric field (ohmic conduction). Moisture and the higher concentrations of nano-filler enhanced charge decay in composite and increased the threshold field of space charge accumulation, which was confirmed by previous pulsed electroacoustic (PEA) measurements.