In order to develop new recyclable DC cable insulation materials, the microscopic morphology and structure, thermal properties, space charge and DC breakdown characteristics of nano-MgO/PP composites were investigated in detail based on the feasibility study of polypropylene (PP) as a high-voltage DC cable insulation material.
The effects of MgO nanoparticles on the microscopic morphology and structure, thermal properties and electrical properties of PP were investigated, and the mechanism of MgO nanoparticles in regulating the electrical properties of PP was explained by testing the charge trap energy level and density distribution.
The results showed that the addition of MgO nanoparticles did not significantly change the crystallinity, crystalline shape, melting temperature and other parameters of PP, and the nano-MgO/PP composite still maintained the excellent thermal properties of PP, and the thermal decomposition onset temperature of the composite was slightly increased compared with that of PP. The addition of MgO nanoparticles can significantly inhibit the injection of homopolar charges into PP and reduce the space charge accumulation.
The composites with the addition of 3phr MgO nanoparticles had the highest DC breakdown strength, which was increased by 29.3% relative to pure PP. The results of the thermally stimulated current test showed that the addition of MgO nanoparticles increased the deep trap density, formed a shielding layer near the electrode and reduced the carrier mobility, thus inhibiting the homopolar charge injection and increasing the DC breakdown field strength.
The study of the microstructure, thermal and electrical properties of PP modulated by MgO nanoparticles can provide a reference for the development of new recyclable DC cable insulation materials.