Dielectric properties of alumina-filled poly (ethylene-co-butyl acrylate) nanocomposites Part II- wet studies

The influence of moisture on the dielectric properties of different types of poly (ethyleneco- butyl acrylate) filled with alumina nanoparticles was systematically investigated by varying the type of aluminum oxide, particle surface treatment and filler content (2, 6 and 12 wt%). The nanoparticles were either unmodified or surface-treated with either aminopropyl triethoxysilane or octyltriethoxy silane. The complex permittivity was measured with an IDA200 dielectric spectroscopy analyzer at applied voltage of 200 Vpeak with frequencies varying between 1 mHz and 1 kHz. The measurements were performed at 25°C and relative air humidities of 24, 54 and 86%. In order to expand the frequency range the HP 4284A precision LCR meter was used for measuring sample impedance at the frequency range of 100 Hz to 1 MHz. From the frequency dependence of dielectric losses it can be seen that absorbed water plays a significant role in determining the dielectric properties of the nanocomposites. The magnitude of tan δ seems to be determined primarily by the particle size and filler content, while the peak frequency is mostly influenced by the amount of absorbed water and the type of particle coating.