Relationship Between Multiscale Structure and Mechanical Hysteresis Loss in Thermoplastic Polyurethane‐Urea Elastomer Films

Abstract

ABSTRACT The trade‐off between lower hysteresis and higher tensile strength of thermoplastic elastomers remains challenging for their various applications in stretchable electronics. In this work, the relationship between multiscale structure and mechanical hysteresis loss of thermoplastic poly(urethane‐urea) elastomers (TPUUs) was investigated. The microphase separation morphology of TPUUs was adjusted using various molecular weights of poly(tetrahydrofuran) (PTMG) and their mixtures as soft segments (SS). The interconnected hard domain (HD) morphology of TPUU was achieved at 13.7 wt% of hard segment (HS) content and using a 7:3 molar ratio mixture of PTMG with molecular weights of 2000 and 1000 g/mol as the SS (PTMG 2K/1K ‐7/3). It demonstrated that the mechanical hysteresis loss of TPUUs was associated with physical network deformation, as well as partial breaking and reorganization of HDs via dynamic hydrogen bonding breaking and reconstruction. The mechanical hysteresis loss of TPUUs with interconnected HD morphology was significantly lower than that of TPUUs with dispersed HD morphology. The TPUU with PTMG 2K/1K ‐7/3 exhibited a tensile strength of 47.14 MPa, hysteresis losses of 9.8% and 2.2% after the 1st and 20th cycles of stretching at 100%, respectively, and a residual strain of 8.7% after 20 cycles of stretching.