Dielectric properties of alumina-filled poly(ethylene-co-butyl acrylate) nanocomposites

The dielectric properties of poly (ethylene-co-butyl acrylate) with 13 wt% of butyl acrylate (EBA) filled with alumina nanoparticles (diameter <; 50 nm) were studied as a function of particle coating and filler content (2, 6 and 12 wt%). The particles were either unmodified or surface treated either with aminopropyl triethoxysilane or octyltriethoxysilane. The complex permittivity was measured with an EDA200 dielectric spectroscopy analyzer at applied voltage of 200 Vpeak with frequencies varying between 1 mHz and up to 1 kHz at different temperatures (25, 45 and 65°C). Measurements are per formed in dry conditions. Pure EBA shows two regions of frequency dispersion in the complex permittivity: a broad relaxation peak in the order of MHz and a characteristic low frequency dispersion that likely is a Maxwell-Wagner response due to a barrier blocking conduction process. Obtained data fits well to a sum of two Havriliak-Negami expressions. Adding nanoparticles to the EBA matrix changes the low frequency dispersion behaviour significantly. Differences in dielectric losses between nanocomposites with different surface treatment seem to be small. The differences in dielectric constant, however, are more pronounced and seem to indicate better dispersion with octylthriethoxysilane surface treatment.