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

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. Published under an exclusive license by AIP Publishing.

Automated summary

This paper investigates the dynamic electrical conductivity of silicone rubber filled with aluminum hydroxide during crystallization. Initial crystallization leads to a reduction in conductivity, with the addition of more ATH fillers lessening the decrease; the development of subsidiary lamellae enhances conductivity, while the growth of rigid amorphous fraction decreases it again.