Varnishes and UL 1446

UL 1446 — Systems of Insulating Materials — General, required a reevaluation of electrical systems. This reevaluation included an upgrading of electrical impregnating insulating varnish to a primary insulation component. A massive program was then undertaken by the resin industry to establish component recognition values for the varnishes. Testing was conducted on all types of varnishes. Each product was tested in accordance with the prescribed ASTM methods. The results of this testing program have provided new insights into the interaction of the insulating varnish with the enamelled wire; that is, a simple system of conductor + enamel + varnish was being studied. The thermal endurance of the varnish is determined by the performance of this simple system. The test program not only provided long needed information about varnish — enamel interaction but also provided expanded knowledge of solventless type products. The additional knowledge helped resolve problems related to the effects of different monomers with the same base resin for polyesters. Further testing also helped resolve problems related to specimen and sample preparations for solventless varnishes. This paper will cover these topics along with a presentation of the related data. It will also explain how these topics are being incorporated into ASTM methods for utilization by the Electrical Industry.