A new potential barrier model in epoxy resin nanodielectrics

The dielectric constant and the conductivity of epoxy resin nanocomposites exhibit a lower value at slight filler loading compared with the host epoxy resin. The electrical strength has an increase and presents an optimal value at filler loading of 1 wt%. The interaction zone between the nanoparticles and the polymeric matrix is considered as an independent region. Accordingly, a new potential barrier model is proposed. Based on the model, carriers are restrained in the interaction zone when nanoparticle is in an isolated dispersion, leading to a decrease in both mobility and density of carriers. As a result, the conductivity decrease and the electrical strength increase. The restriction of dipole movement in the interaction zone and the increase of free volume are collectively contributed to the reduction of the dielectric constant. With increasing filler loading, the thickness of the interaction zone extends due to the overlap of the interaction zone, even a conductive path occurs when filler loading exceeds the percolation threshold, leading to a great increase in both mobility and density of carriers. Consequently, the conductivity increase and the electrical strength decrease. The increase of the dielectric constant is chiefly ascribed to the particles.