The use of FTIR spectroscopy for determination of the optimal regime of enamelling process with polyesterimide enamels

This paper deals with the kinetics of curing and thermal degradation processes of commercially available THEIC-polyesterimide-based enamels. All investigations were performed on the enamel samples from enamelling wires manufactured with real equipment. Fourier transform infrared (FTIR) spectroscopy was employed to monitor the polymer cure and thermal degradation during wire enamelling. It has been found that process of polymer cure is accompanied by the reducing of hydroxyl group concentration and consequently by the reducing of the OH groups absorption intensity. Detailed study of the hydroxyl IR absorption region identified separate bands sensitive to the polymer structurization and destruction. It has been found that the increase of the OH intensity of carboxylic groups at 3228 cm^-1 can be utilised to monitor the thermal degradation. It was shown that analysis of the hydroxyl groups region in the wire enamel IR-spectra allows determination of the optimal enamelling regime for the equipment. IR-spectrum of enamel film from enamelled wire has some additional information about physical structure of the polymer which may be used for prediction of some macroscopic wire properties. For example, area of the absorption band at 3630 cm^-1 is responsible for the value of prestretch in the flexibility test