Putty is an encapsulation polymer-insulating material that protects the windings of large motors, generators, and transformers from coronas, radiation, and heat. It is used as a barrier insulation in windings to make void-free and air-gap-free structures. A two-pack epoxy putty has been developed with inorganic-filler powder materials. The cured putty system has very high adhesion to substrates, and it is flexible enough to absorb the heating and cooling cycles of coils without cracking after long-time use. The mechanical and electrical properties of the putty have been determined with methods of the American Society for Testing and Materials. The temperature class of the putty is 203 degrees C. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 117: 2310-2315, 2010