Study on nonlinear conductivity of copper-titanate-calcium/liquid silicone rubber composites

Polymer matrix composites with excellent electric field dependent nonlinear conductivity and high breakdown strength are widely used in cable accessory insulation materials. The addition of CaCu
3
Ti
4
O
12
(CCTO) can impart nonlinear conductivity to the silicone rubber materials, which can be used to improve the electric field distribution in the cable accessory. In this study, the two-component liquid silicone rubber (LSR) was chosen as polymer matrix, and CCTO nanoparticles (CCTO NPs) and CCTO nanofibers (CCTO NFs) were respectively prepared by sol-gel method and electrospinning and added into LSR polymer matrix respectively for obtaining CCTO NPs/LSR and CCTO NFs/LSR composites. The microstructures of the fillers and composites were characterized by scanning electron microscopy and X-ray diffraction. The conductivity and breakdown strength of composites at different temperatures were investigated systematically. The results showed that the electric field dependent nonlinear conductivity of composites became more and more obviously with the increase of filling content of the fillers. In addition, comparing the conductivity, breakdown strength and electric field distribution simulation of CCTO NPs/LSR with that of CCTO NFs/LSR composites, it could be found that CCTO NFs/LSR composite at a lower filling content (3 vol %) could homogenize the electric field distribution much more effectively. The results provide an effective way to solve the problem of the electric field distribution in cable accessory.