Study on the Corona-resistance of a Solventless Varnish Modified by Nano Alumina

To improve the electronic corona-resistance of a unsaturated polyesterimide solventless impregnating varnish,nano alumina was added into the varnish. Test show that dielectric loss of the hybrid varnish films are increaced along with the increace of nano alumina,and corona-resistance life extend obviously,observation with SEM show that nano alumina is scattered uniformly in the resin matrix.Meanwhile,nano alumina has negative effects on the viscosity and toughness of the varnish.