Impedance and thermal conductivity properties of epoxy/polyhedral oligomeric silsequioxane nanocomposites

The impedance and thermal conductivity properties of prepared organic epoxy/polyhedral oligomeric silsequioxane (POSS) nanocomposites were studied. The measurements of the impedance were carried out using the impedance technique as a function of applied field frequency range from 20 kHz to 1 MHz, temperature range from 20 degrees C-110 degrees C, and POSS filler concentrations 5, 10, and 20wt%. The AC conductivity and dielectric properties were determined from the impedance data. It was found that the AC conductivity and dielectric constant are increased by increasing the POSS content in the nanocomposites. The calculated activation energy varies with the filler content, temperature, and applied frequency. The observed electrical results fit approximately the reported equations concerning the AC conductivity of the prepared nanocomposites. The dielectric behavior was explained on the basis of the interfacial polarization, dipolar polarization, and decrease in the hindrance produced by the polymer matrix. The thermal conductivity of the prepared nanocomposite was studied as a function of temperature, and POSS concentration. It was found that the thermal conductivity is enhanced by the addition of the POSS content and temperature. During the heating process, the phonons are activated and electrons hopp to higher localized energy states producing enhancement in the thermal conductivity. Furthermore, correlations between the observed physical properties as thermal conductivity, storage modulus, and glass transition temperature of the nanocomposites are presented.