may contain small amounts of additives such as acid scavengers corrosion inhibitors biocides flame retardants and antioxidants these novel dielectric media can be used as the sole impregnant or in combination with other conventional dielectric media e g dioctyl phthalate surfactants which lower the surface tension of the dielectric medium can also be added conversely other ingredients may be added to these dielectric media which during impregnation selectively migrate into the plastic film and increase the wettability critical surface tension of the film and thereby make impregnation of the capacitor winding more facile these dielectric compositions are used to impregnate a wide variety of polymer films e g polyethylene polypropylene polyesters polycarbonate polysulfones polyamides vinyl polymers etc but they are especially useful in capacitors incorporating fluorinated polymer films e g polyvinylidene fluoride polyvinyl fluoride polytetrafluoroethylene and their copolymers fluorinated polymers have a low critical surface tension and therefore will resist wetting by most fluids optimum wetting i e free spread or zero contact angle of the liquid on a surface is only obtained when the surface tension of the liquid is less than the critical surface tension of the solid the compositions described here offer the important property of low surface tension along with other desirable properties such as high dielectric constant good thermal stability and low viscosity.