Compounding, Structure and Dielectric Properties of Silica-BOPP Nanocomposite Films

This study presents preliminary results on the morphology, structure and dielectric properties of laboratory scale cast and biaxially oriented silica-PP films, currently being developed in the European project GRIDABLE. Space charge measurements on the thick cast films indicated a reduction of positive space charge and faster depolarization characteristics upon inclusion of nano-silica, being indicative of reduction of trap depth and density distribution in comparison to neat PP. Likewise, for the biaxially oriented silica-PP thin films, increased amount of shallow traps and a reduction of concentration of traps in the deep trap range (∼ eV) were observed. Nano-silica was also found to reduce the dielectric loss at high temperatures in the frequency range appropriate to use. Such dielectric property modifications can potentially lead to benefits for insulation reliability and lifetime, especially at higher temperatures. A two-step compounding via a master batch approach was also found to be a viable option for the up-scaling of nanocomposite production.