Study on Microphase Separation of Waterborne Polyurethane by the Infrared Spectroscopy Peak Fitting

A series of waterborne polyurethane (WPU) with different soft segment structures were sythesised, and the effects of the structure and molecular weight of the soft segment on the degree of PU microphase separation were evaluated by the infrared spectroscopy (FTIR) computer peak fitting. The experiment results indicated that phase separation between hard and soft segments of poly (ether–urethane) was more significant than poly (ester–urethane), based on the qualitative analysis on the N–H stretching region of the FTIR spectrum. And the qualitative analysis on the carbonyl stretching region showed that PU with lower soft segment molecular weight had a higher relative amount of hard segment, and possesses higher microphase separation degree. The addition of polyether soft segment PEG had an internal plasticization by actuating the PCD molecular chain. Therefore, it becomes easier for PU to conduct structure adjustment and increased the phase separation degree.