Heat resistant magnet wire insulation based on acrylic enamels

Recent social requirements of environment, occupational health and saving resources invite us to reassess acrylonitrile copolymers as base materials for magnet wire enamels, because of its suitability to formulate water dispersion systems. Ercusol®, Cavalyt®, and MEDlrf®. ¹) (Mitsubishi Electric Corp.) are recent examples. In spite of the above advantages and its reasonable cost, the limitation of thermal stability seems to prevent the penetration to practical application. We have reported a possibility to break through this limitation by "dual coated acrylic enamel "²) Temperature classes of 150° to 180°C could be achieved by selecting the composite insulation layer, though the mechanism of increased heat resistance was not clear. A study which followed the above finding revealed that the unusually heat resistant wires can be derived through the formation of thermostable heterocyclic ring from acrylonitrile copolymers in nonoxidative environment in the early stages of thermal aging. Details of the mechanism of the formation of the heat resistant structures and changes in thermal and mechanical properties during heat treatment will be reported in this paper.