Thermoplastic polyurethanes (TPUs) are random block copolymer materials whose properties can be adapted to an extremely wide range of applications. This is the consequence of the fact that the materials consist of 3 chemical components which are chosen from extensive classes. Essential for the material properties of TPUs is a morphology consisting of hard domains in a soft matrix phase. Today, powerful X - ray systems allow to register the variation of the morphology in situ. This serves to fundamentally understand the relationship between the chemical structure and the properties of the material.

　　TPU materials have been prepared from proven formulations of chemical components. The TPUs are monitored by small-angle X-ray scattering (SAXS) during either straining or melting and solidification. The morphology evolution under load is recorded. Corresponding mechanisms are identified and quantified. The strengths of these mechanisms relate both to the chemical formulation and to the material properties. The elucidation of these relationships serves to predict the properties of polyurethanes.