Polyurethane thermal effects studied using two-dimensional correlation infrared spectroscopy

Two-dimensional (2D) correlation infrared spectroscopy was used to investigate the thermal effects of polyurethane. Five structure transitions were observed at around 65 °C, 150 °C, 190 °C, 235 °C and 265 °C using moving windows two-dimensional correlation spectroscopy (MW2D). 65 °C and 150 °C were the glass transition temperature of hard segments (HS) and viscous flow temperature, respectively. 190 °C, 235 °C and 265 °C were three thermal degradation temperatures of HS. It was proved that MW2D was sensitive to the polymer structure transitions. The overlapped NH and CO absorbance bands were identified and analyzed by generalized two-dimensional correlation infrared spectroscopy (2DCOS). The evolvements of the different types of NH and CO during the transitions were obtained. The results showed 2DCOS could improve the analytical ability of in-situ FITR. Both the two 2D correlation methods are helpful for the polymer degradation mechanism studies.