The radiation resistance of some common insulating varnishes

The radiation resistance of three popular families of insulating varnishes was investigated. The materials selected included oil modified polyesters, solventless epoxies, and unsaturated sol-ventless polyesters. A representative material from each of the families was evaluated in terms of electrical and mechanical performance, exposed to an intense beam of electron radiation, and then re-evaluated. The radiation dosage selected was based on current industry standards for anticipated exposure during a normal in-service life of 40 years. Test results revealed that certain types of insulating varnishes exposed to this type of radiation are affected to a much greater degree than others. This information should be of interest to design engineers involved in the selection of materials for use in the manufacture of motors which may be destined for use in radioactive environments.