Composition Effects of Thermoplastic Segmented Polyurethanes on Their Nanostructuring Kinetics with or without Preshear

In this work, the structuring mechanism from the molten state of various thermoplastic polyurethanes was analyzed with respect to their composition [polyether or polyester soft segments (SSs), aromatic or aliphatic hard segments (HSs)]. As a preliminary study, the molar mass evolution of the materials with the temperature was quantified. Then, based on rheological experiments and in situ rheo-small angle X-ray scattering (SAXS) measurements, the structuring was examined at different temperatures and, particularly, the effect of a preshear treatment was analyzed. The temperature effect can be accounted by an Arrhenius-like law with an activation energy depending mainly on the HS nature. Moreover, the shear induced structuring phenomenon is highlighted for all the studied thermoplastic segmented polyurethanes. Nevertheless, for the studied range of shear treatments, the SAXS analyses did not reveal any specific orientation. Finally, arguments based on the modification of the quench depth (Delta T = T(ODT) - T) by the shear are given to explain the shear induced structuring phenomenon. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 801-811, 2011