1989 report on dual coated magnet wire-a comparison of class H polyesterimide compared to class H polyester

As the demand for higher thermal properties increased, enamel producers responded with polyesters and polyesterimides which met the requirements for better heat shock and thermal life and higher thermal plastic flow. The problems encountered using these enamels in high-speed winders were solved by the magnet wire producers with the application of top coats. To illustrate the advantages obtained by the use of a top coat, abrasion resistance, heat shock, burnout, and resistance solvents are reviewed. The enamels used in the study were high and low solid variations of polyester, polyesterimide, and amideimide; the nylon used was unmodified. Top coats of polyamide (nylon) and polyamideimide were found not only to improve the abrasion resistance of the film insulated magnet wire but also to help in improving heat shock, burnout, and chemical resistance. Polyesterimides continue to maintain their advantage in physical properties over polyesters using the same construction