Polymer nanocomposite dielectrics - the role of the interface

The incorporation of silica nanoparticles into polyethylene increased the breakdown strength and voltage endurance significantly compared to the incorporation of micron scale fillers. In addition, dielectric spectroscopy showed a decrease in dielectric permittivity for the nanocomposite over the base polymer, and changes in the space charge distribution and dynamics have been documented. The most significant difference between micron scale and nanoscale fillers is the tremendous increase in interfacial area in nanocomposites. Because the interfacial region (interaction zone) is likely to be pivotal in controlling properties, the bonding between the silica and polyethylene was characterized using Fourier transformed infrared (FTTR) spectroscopy, electron paramagnetic resonance (EPR), and x-ray photoelectron spectroscopy (XPS). The picture which is emerging suggests that the enhanced interfacial zone, in addition to particle-polymer bonding, plays a very important role in determining the dielectric behavior of nanocomposites.