ABSTRACT
Since the 1930s, synthetic polymers have been developed and widely used as electrical insulating materials in the electrical engineering field due to their high breakdown strength of up to ~109 V/m and high resistivity of 1016 ∙ m. Tremendous efforts have been made to understand electrical breakdown in polymers. In general, the breakdown strength of polymers depends on a number of factors amongst which are the thickness, temperature and pressure. These factors interact with the complicated structures and morphology of polymeric materials, which makes breakdown processes very difficult to understand. For applications in the electrical engineering, polymer composites are widely used to improve mechanical, thermal or electrical properties. However, the breakdown strength of the polymer composites are usually decrease due to the fillers, which can be regarded as the defect in the polymer matrix.Electrical breakdown of polymer nanocomposites not only depends on the polymer matrix, but also is significantly influenced by the introduced nanofiller. Consequently, polymer nanocomposites can show encouraging dielectric breakdown properties [1-3]. A majority of experimental results indicate that many factors influence the breakdown properties of nanocomposites, such as the modification of nanofillers [4, 5], nanofiller loading and type [1, 6], cohesive energy density (CED) and the glass transition temperature (Tg) of the polymer [7, 8]. For the nanofillers, the physicochemical characteristics is very crucial for the breakdown performance of the nanocompostis. The interaction of nanoparticles (NPs), which have different polar or non-polar functional groups on their surface, with the polymer matrix influences the breakdown properties. In addition, changes in morphology due to the incorporation of NPs, particularly for semicrystalline polymers, are of great importance to the breakdown performance. It is well acknowledged that the interface between nanofiller and polymer dominates the dielectric breakdown performance [9-11]. Therefore, many researchers pay considerable attentions to the physical and chemical properties of the interface and try to tailor the interface by physical and chemical methods in order to obtain enhanced dielectric breakdown properties.
