Investigation of Electrical Properties of $\text{TiO}_{2}$/EPDM Composites with Different Morphologies

In this work, $\text{TiO}_{2}$ nanofibers $(\text{TiO}_{2}$ NFs) with micron-nano size are prepared via electrospinning, and composites with $\text{TiO}_{2}$ nanoparticles $(\text{TiO}_{2}$ NPs) and $\text{TiO}_{2}$ NFs as fillers are prepared using EPDM as the matrix. The effect of $\text{TiO}_{2}$ with different morphologies on the electrical properties of the EPDM matrix has been comparatively analyzed and systematically investigated. The results show that the $\text{TiO}_{2}$ NFs/EPDM exhibit nonlinear conductivity at a lower content compared to $\text{TiO}_{2}$ NPs/EPDM composites. The threshold electric field of 18 wt.% $\text{TiO}_{2}$ NFs/EPDM is 10.8 kV/mm and the nonlinear coefficient is 2.77. With the content of $\text{TiO}_{2}$ NPs and $\text{TiO}_{2}$ NFs increases, the breakdown field strength of the composites gradually decreases. At the same content, the breakdown strength of $\text{TiO}_{2}\ \text{NFs}/\text{EPDM}$ is slightly lower than $\text{TiO}_{2}$ NPs/EPDM; the dielectric constant and dielectric loss of $\text{TiO}_{2}$ NFs/EPDM composites are slightly higher than that of $\text{TiO}_{2}$ NPs/EPDM composites. The simulation results show that the 18 wt.% $\text{TiO}_{2}$ NFs/EPDM can better homogenize the electric field, reduce the electric field at the end of the shielding tube, and improve the reliability of the safe operation of cable accessories. This work provides an effective method of preparing electric field graded materials.