In rigid TPUs, the free volume is low due to numerous hydrogen bonds between the various rigid segments linked to the urethane groups. PHO-hexyl's action as a plasticizer is therefore multiple, due to its chemical structure. PHO-hexyl's ester and urethane groups can form interactions with TPU urethane groups, in particular. TPU-plasticizer interactions thus reduce TPU's own intra-and interchain interactions. They also minimize potential phase separation (demixing) with plasticizer volatilization or migration towards the sample surface. The alkyl-pendant chains of the HO units allow free volume to be gained by spreading the rigid TPU chains apart, which also reduces interactions between them. PHO-hexyl therefore has also a great potential as a plasticizer for rigid TPUs, even in small content. This neat rigid TPU could not be directly shaped by thermo-compression, as it was far too stiff and brittle to be demolded (Figure ). After plasticizing with 15% DPHP:DIDP or PHO-hexyl, the TPU-based materials could be processed and shaped into films. This clearly demonstrates the value of plasticizing rigid TPUs, opening up a whole new field of applications. The plasticized materials were then characterized in terms of mechanical properties using uniaxial tensile tests. The results are shown in Figure . The εmax of the two plasticized TPUs are similar, while the E and σmax are about twice as high for the TPU plasticized with PHO-hexyl.