Investigation of tensile behavior and molecular structure of the thermoplastic polyurethane sheets injection molded at different mold temperatures

Abstract

AbstractThis paper aims to investigate the influence of the mold temperature on the mechanical responses at different ambient temperature and molecular structure of the injection molded TPU sheets. The tensile properties of the TPU sheets prepared at different mold temperatures were obtained at different ambient temperatures. As the mold temperature increases, both the elongation at break and tensile strength of the specimens increase. The specimens show yield behavior during stretching at −30 and −50°C. The microstructure of the TPU sheets was characterized by DMA, AFM, and birefringence. The results show that the higher mold temperature can reduce the aggregation of hard domains because of the higher mobility of the hard segments. In‐situ SAXS and WAXS measurements were carried out at −30°C test temperature to exhibit the evolution of the microstructure during stretching. When the specimens are prepared at 40°C mold temperature, the hard domains are destroyed and difficult to orient along the stretching direction. In contrast, the hard domains begin to be deformed and oriented along the stretching direction above the yield strain when the specimens molded at higher mold temperature. The above microstructure evolution is consistent with the tensile behavior of the TPU specimens.