Effect of multiphase content on temperature-dependent electrical conductivity in silicone rubber composites

Abstract

To investigate how the multiphase structures affect the electrical conductivity in semi-crystalline polymer composites, herein, an accurate multiphase content calculation method is proposed and verified, which combines amorphous phase information in broadband dielectric spectroscopy and crystalline phase information in differential scanning calorimetry. Taken aluminium hydroxide (ATH) filled silicone rubber as an example, it is found that the rigid amorphous fraction (RAF) corresponding to the chains constrained by crystals (RAFcry) is not linearly increased with crystalline fraction (CF). Compared to non-isothermal crystallisation, RAF caused by ATH/silicone rubber interface (RAFint) after isothermal crystallisation at 213 K changes little, while mobile amorphous fraction and RAFcry is attenuated and CF is strengthened. Based on the calculated structures of ATH filled silicone rubber, activation energy of conductivities during cooling is dominated by the thermal transition for conductive ions and shortened distance among the conductive ions through shrunk volumes of the amorphous phase. Our findings deepen the understanding of multiphase content in semi-crystalline polymer composites and its relationship with electrical conductivity, which can be applied in manipulating electrical performance of semi-crystalline polymers by fillers.