Effect of filler concentration on dielectric behaviour and on charge trapping in PP/clay nanocomposites

Nanocomposites obtained from polypropylene base materials and organophilic layered silicate as nanofiller might be a great source of innovation for the development of advanced electrical devices. Previous investigations on dielectric and electrical properties of such nanocomposites with either isotactic (iPP) or syndiotactic (sPP) polypropylene as matrix have shown that trapping properties are highly modified by the presence of nanofillers. A reduction of space charge accumulation under DC stress has been shown. In this communication, we report on electrical properties using dielectric and photoluminescence spectroscopy. Dielectric spectroscopy has been used to characterize ionic conduction and to evaluate the effect of the filler concentration on the dielectric permittivity. A relaxation process has been observed at high filler concentration, high temperature and low frequency. Spectral analysis of photoluminescence was performed with the aim of inferring the nature of trapping centers. It appears that nanocomposites made of iPP and sPP exhibit different behaviours.