Characterization of impregnating varnish with silica nanofiller

The nanocomposite has been prepared on the basis of the siliconized polyester impregnating varnish added with nanosilica by using the own patented method. The properties of the nanocomposited and standard varnishes were determined and compared. A clear increase of bond strength and thermal endurance was found although the most improved property have appeared the resistance to partial discharges under pulse voltage 20 kHz/1.1 kV. While the pure varnish lifetime was only 5 minutes, after adding of nanosilica no failure appeared even after 100 hours. Other polyester varnishes modified earlier by us with nanosilica have also shoved improved durability but the lifetimes reached only about 100 minutes. It is to be supposed that the kind of a base polymer is the matter. The siliconized polyester varnish with nanosilica shows much better resistance to partial discharges than unsiliconized one.