Effect of TiO₂ modified with dopamine and Silane coupling agent on the electrical properties of PMIA insulation paper

Poly-m-phenyleneisophthalamide (PMIA) with excellent chemical stability and breakdown strenth is regarded as the next generation of insulating paper in power system. However, the basic intensity of PMIA is not enough to match its operating cost, and it is promising to enhance the performance by nano composition. In this paper, the influence of nano-TiO(2)ith a mass fraction of 1 to 5 wt% on insulating properties is studied, including breakdown voltage and bulk conductivity. The silane coupling agent aminopropyltriethoxysilane (APTES) together with the polydopamine (PDA) are used for modifying the fillers interface. The results show that, APTES covalent grafting and PDA physically coating can improve the dispersion and compatibility of nano-TiO2 in aramid fiber matrix, thus regulating the interface trap characteristics and reducing the probability of electric field distortion in insulating paper. When the modified TiO2 content is 2 wt%, the breakdown voltage is the highest, which is 23.9 kV/mm, 54% higher than that of pure aramid paper. In addition, this article discusses the modification mechanism from molecular dynamic simulation and trap characteristics. Based on molecular dynamics calculation, three interface models of PMIA-TiO2, PMIA-TiO2/APTES, PMIA-TiO2/APTES/PDA are constructed, and the synergistic effect of PDA is confirmed from the microscopic level.