Nanoparticle dispersion and distribution in XLPE and the related DC insulation performance

In this paper, loading content was adjusted and nanoparticle surface modification by silane coupling agent was applied to obtain different XLPE/TiO₂ nanocomposites. Polymer surface etching, a traditional method, was innovatively and effectively used to characterize the nanoparticle dispersion and distribution in nanocomposites. Distinct scanning electron microscope images of nanoparticle dispersion were obtained. It was proved that the surface modification improved nanoparticle dispersion, which was analyzed to relate directly to DC insulation performance and morphology. The introduction of nano-TiO₂ decreased DC conductivity, suppressed homocharge injection, enhanced DC dielectric strength, increased crystallinity and changed morphology. And well nanoparticle dispersion at same loading content achieved by surface modification had positive cooperative effect to the influence above. DC breakdown strength was increased by 13.5%. Decrement of injected homocharge density was calculated, and it can reach 91.5 μC·m-2. Moreover, the non-uniform distribution of nanoparticles in semi-crystalline polymer based nanocomposites was first proposed and discussed. The nanoparticles can be divided into four regions, the boundary zone, the amorphous zone, the nucleation zone and the inter-lamella zone.