Effect of Surface-Modified TiO2 and MgO Nanoparticles on Dielectric Permittivity and Breakdown Strength of PP Nanocomposites

This work focuses on the effects of surface-modified nanofillers with various polar silane coupling agents on dielectric permittivity and dielectric breakdown strength of PP nanocomposites. Surface functionalization of nanofillers is implemented using an anhydrous technique with three different surfactants. These surface-modified nanofillers are mixed with polymers at fill grades of up to 5% by weight, prepared by a solution blending method. Thermogravimetric analysis confirms the presence of surface functionalization and the desired nanofiller amount. Dielectric permittivity values tend to rise as a function of filler content, and notably the dielectric loss of TiO2 nanocomposites is significantly increased below 0.1 Hz. MgO nanocomposites have overall lower dielectric losses than TiO2. AC breakdown of PP is significantly improved with modified TiO2 and MgO at 2.5%, while other fill grades have less pronounced effects. Ethoxy-modified nanoparticles with long chain hydrolysable group show overall the best dielectric properties.