Superiority in partial discharge resistance of several polymer nanocomposites

Polymer nanocomposite is defined as a polymer with small amounts of nanometer size inorganic fillers homogeneously dispersed. This nano material is potentially applied to electrical insulation to power apparatus and cables. It was found among them that partial discharge resistance exhibits supermarked improvement by nanostructuration. The paper demonstrates the superiority of the following nanocomposites in partial discharge (PD) resistance over neat and micro-filled polymers, and comparative evaluation of thier PD resistance. Futhermore, it describes how it takes place as its mechanisms. (1) polyamide/layered silicate nanocomposites (2) epoxy/layered silicate nanocomposites (3) epoxy/silica nanocomposites (4) epoxy/titania nanocomposites (5) epoxy/alumina nanocomposites Both base polymers and polymer nanocomposites were subjected to ac voltage (60Hz and 720 Hz) using the IEC (b) electrode system and the rod-gap-plane electrode, and evaluated by scanning electron microscopy, atomic force microscopy, mechanical profilometry, laser microscope, X-ray diffraction spectroscopy and energy-dispersive X-ray spectroscopy. From erosion depth study and associated physical investigation, it is concluded that the addition of several wt% nano-fillers is very effective to increase PD resistance of polymers such as polyamide and epoxy. Epoxy/silica (12nm) nanocomposite with silane coupling treatment is the best of all the tested nanocomposites, partly because thier interface is considered to be solid. There is a filler size effect from μm down to nm on PD resistance. Coupling agents would help improve the degree of PD resistance to a certain degree. Morphological change taking place in a nanostructuration process is effective in some cases. The first principle for the superiority of nanocomposites in PD resistance is definitely the effect of three dimensional fine partition of polymer matrix that could be made by nano fillers. There are some other important effects possibly arising from filler-matrix interfaces, polymer morphology around the interfaces, and/or PD self-produced substances.They are also interpreted using a newly proposed multi-core model that is considered to be rather universal to all dielectric properties and related phenomena.