Effects of Filler Calcination on Structure and Dielectric Properties of Polyethylene/Silica Nanocomposites

This paper reports on an investigation of the effects of calcination on the structure and dielectric properties of polyethylene/silica (SiO2) nanocomposites. Calcination temperatures of 600 and 900 degrees C have been used in order to modify the surface chemistry and surface structure of the SiO2. The results show that, after calcination, the concentration of surface hydroxyl groups and water molecules around SiO2 and within resulting nanocomposites is reduced. The real permittivity of nanocomposites containing calcined SiO2 decreases compared to nanocomposites based on uncalcined SiO2. The DC breakdown strength of nanocomposites containing calcined SiO2 becomes higher than those containing uncalcined SiO2. In contrast, AC breakdown was found not to be significantly affected by addition of any of the silicas considered here. The use of calcined nanofillers can have positive effects akin to the use of chemically functionalized nanofillers in enhancing the dielectric properties of nanocomposites; both approaches remove polar surface hydroxyl groups.