Superhigh strength polyurethane materials with oriented microdomains produced through mechanical deformation

Abstract

Self-reinforcement is a preferred strategy to achieve high tensile strength polymer materials. Sparse work has been reported in this aspect on thermoplastic polyurethanes (TPUs). Three commercial TPUs, two polytetramethylene ether glycol (PTMG)-based TPUs (coded as MDIPTMG and TDIPTMG) and one polycaprolactone (PCL)-based TPU (MDIPCL) were chosen to study the dependences of mechanical tensile properties on the microstructures. Fourier transform infrared spectroscopy, thermogravimetric analysis and atomic force microscopy were used to characterize the chemical compositions, thermal stabilities and microphase morphologies. The mechanical properties such as tensile strength and the Young's modulus of the three TPUs were greatly improved through step-cycle tensile deformation, especially for MDIPTMG and MDIPCL. The true stress-true strain curves indicated that point A (the end of the Hooke range) and point B (the yield point) located at about same strains, whilst point C (the formation of oriented microdomains) for MDIPTMG and MDIPCL located at a much lower strain than that for TDIPTMG. In-situ small-angle X-ray scattering further revealed that the hard microdomains of MDIPTMG and MDIPCL could transform to oriented microstructures at the strains above 200%, consistent with the critical strains at point C . The oriented microstructures could be preserved, which played a significant role to achieve high strength TPUs, with a potential to widen their practical applications. • Superior TPUs with super high tensile strength were produced. • The oriented microdomains played a crucial role for TPUs. • Simple tensile deformation processing is applicable to TPUs.