High temperature aging of enameled copper wire — Relationships between chemical structure and electrical behavior

This work presents the physico-chemical behavior of several enameled copper wires systems such as PolyEsterImide (PEI)/PolyAmideImide (PAI) or PAI based multi layers compared to PolyImide (PI) which remains the basic enamel material for high temperature applications. The structural, thermal and electrical properties of these systems have been investigated before and after aging in the 200°C–400°C temperature range by thermogravimetric analysis (TGA), ATR-FTIR microscopy, thermomechanical analysis (TMA) and dielectric relaxation spectroscopy (DRS). It has been particularly interesting to carry out physico-chemical analysis directly on enameled wires to improve the understanding of their thermal and electrical behaviour. Dielectric spectroscopy has indicated a loss of insulating properties during the thermal cycle especially for PEI-containing enamels whereas the properties of PI and PAI have been maintained. TGA and IR analyses have not only allowed confirming the PI and PAI high thermal performances, but have also given information on the thermal and chemical stability of PEI/PAI. Such investigations could be helpful for improving the enameled wire high temperature performances.