A comparison of non-isocyanate and HDI-based poly(ether urethane): structure and properties

This work synthesized a group of NIPUs and HDIPUs via isocyanate-free route and isocyanate route. The structure, crystallization behavior, morphology and phase separation behavior of NIPUs and HDIPUs were systematically studied and compared in this work. The crystallization behavior and phase structure of NIPUs and HDIPUs were studied by DSC, WAXS, SAXS, and AFM. Mechanical properties were measured and analyzed to correlate with the solid state structures. The results indicated that the structural distinction between NIPU and HDIPU was originated from the hard segment. The urea content in the hard segments of NIPUs was much higher than HDIPUs. The transesterification of two urethane group and the carbamate metathesis polymerization are the two possible reasons for the formation of urea groups. There were more disordered phase in the hard phase due to the random urea-urethane hard segments of NIPUs, and the crystallinity of the hard phase was lower. The compatibility between the hard phase and the soft phase of NIPUs was increased, resulting in their poor thermal and mechanical properties.