Dynamic electrical conductivity induced by isothermal crystallization in aluminum hydroxide filled silicone rubber

Abstract

In this paper, taking aluminum hydroxide (ATH) filled silicone rubber as a model composite, we report the “n-shape” dynamic electrical conductivity during isothermal crystallization in nonconductive particles filled insulating polymers. During the initial crystallization, rapid growth of dominant lamellae blocks the transport path of impurity ions, contributing to the remarkable reduction of conductivity. Addition of ATH fillers could reduce the silicone rubber content and randomness of crystals formation, lessening the amplitude of decreased conductivity. Afterward, the silicone rubber composites further shrink due to the development of subsidiary lamellae. It results in low activation energy of ion migration and thereby enhances conductivity, whose amplitude is positively related to the crystalline phase. Finally, continuous growth of rigid amorphous fraction with reduced chain mobility impedes the ions transport, decreasing the conductivity again. The growth of rigid amorphous fraction is accelerated in silicone rubber with more ATH fillers because of more constraint of ATH on molecular chains. Our findings afford a simple means to manipulate insulation performance of nonconductive particles filled semi-crystalline polymers and provide a guideline for their use in real operation.