In this study, we present the results of the influence of surface modification of TiO2 nanoparticles on the short-term breakdown strength and space charge distribution of low-density polyethylene (LDPE). A polar silane coupling agent N-(2-aminoethyl) 3-aminopropyl-trimethoxysilane (AEAPS) was used for the nanoparticle surface modification. Despite agglomeration and a poor interface compared to untreated nanoparticles, it was found that the incorporation of polar groups onto the nanoparticle surface improved both the dielectric breakdown strength and space charge distribution as compared to samples filled with untreated nanoparticles. Microstructure studies showed that the presence of polar groups on the TiO2 nanoparticle surface did not evidently affect the degree of crystallinity, crystalline morphology (except for internal spherulitic order), and chemical structure of the polymer matrix. The improved dielectric breakdown strength was therefore concluded to be directly due to beneficial effects related to the variation of the electrical features at the particle surface due to introduction of polar groups. For the same reason, with the use of surface modified nanoparticles, formation of space charge was suppressed.

Highly nonlinear electrically insulating materials have applications in high voltage cable applications. In this contribution, nanocomposites were prepared by blending ZnO nanoparticles or ZnO nanoparticles treated with aqueous SnX 2 (X= F or Cl), with EPDM (ethylene propylene diene monomer). The treated powders were a heterogeneous mixture of ZnO and SnO and show enhanced nonlinearity compared to pure ZnO. It was demonstrated that at certain filler concentrations, the resulting nanocomposites exhibited highly nonlinear I-V characteristics. We attempt to draw correlations between the phases present in the powders, the morphology, the nonlinear behavior of the powders, and the composite nonlinear I-V properties.