The tendency of decrease dielectric permittivity and dissipation factor is surprisingly different from other plastics, either
thermoplastic, thermostable or elastomers [31], which always increase with filler content. Thanks to the very low concentration of BaTiO3 inside rubber films, this unexpected behaviour should be explained by the synergistic combination of a
non-polar polymer chain, with a homogenous amorphous phase distribution (as proved by SEM and DSC), and a very well
wetted oxide fillers with nanometric particle size added by sonication. The smallest and superior filler distribution helped
the polymer matrix to decrease voids in the interface between particle and elastomer, increasing the storage energy of the
composite material, and then decreasing the interfacial polarisation or the accumulation of charge in a local environment.