Primary thermal degradation effects on the polyurethane film

Primary thermal degradation effects on polyurethane at 175 °C are studied by time-dependent IR spectra and two-dimensional (2D) correlation spectra. It was observed that the hard segments in polyurethane would degrade first, and the urethane group with the bonded CO was more stable than that with the free CO. The main structure changes at 175 °C were caused by the degradation of urethane linkages. Urethane linkages firstly experienced two pathways to degrade resulting in the formation of isocyanate, alcohol, secondary amine and carbon dioxide. The produced isocyanates were highly reactive, and would react with the secondary amine forming urea which was more stable than polyurethane.