Revisiting thermoplastic polyurethane,from composition to morphology and properties

Thermoplastic polyurethanes (TPUs) are among the most versatile engineering polymers. The presence of hard and soft segments on their backbone and specific hydrogen bond interactions between the hard segments, provide TPUs with outstanding engineering properties while rendering them as very complex systems to study. Knowledge of morphology–property relationship is essential for TPUs since their thermal and mechanical behavior are directly dictated by their complicated morphology. In this research, TPU morphological features related to the hard segment content (HSC) were explored in tandem with system macroscopic properties. It was observed that TPUs display multiscale phase separated morphology with specific morphological features dependent on the HSC. At a certain critical HSC, an interconnected network of hard segments was formed which resulted in significant changes in TPU properties. This was explained in analogy with percolation phenomena in filler reinforced systems and considering the hard segments as reinforcing agent. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1553–1564