Effects of Reserved Shish Crystals and Hot Stretching on UHMWPE High-Strength Films

Ultrahigh molecular-weight polyethylene (UHMWPE) high-strength films, with their outstanding properties, can be widely used in various fields. However, their mechanical properties still need to be improved, making it crucial to explore the preparation process for UHMWPE high-strength films. By adjusting both the stretching temperature and draw ratio (DR), a multistage stretching process was explored. Unlike traditional UHMWPE gel-spinning methods, a lower dissolution temperature was used to obtain gel films with reserved shish crystals in this study. Wide-angle X-ray diffraction, small-angle X-ray scattering, ultrasmall-angle X-ray scattering, differential scanning calorimetry, and scanning electron microscopy were utilized to investigate the structure–property relationship under different conditions. Prestretching the gel film with solvent allowed for a higher DR, and the subsequent hot poststretching of the extracted film without solvent reduced voids and significantly improved the mechanical properties. Unlike room-temperature prestretching, hot stretching, especially near the melting temperature, favored the orientation of crystals along the stretching direction. Then, the hot poststretching stage further promoted the transformation from shish-kebab to shish crystals. Through sufficient hot prestretching of UHMWPE gel films with reserved shish crystals at 115 °C combined with extracted film poststretching, the tensile strength of 3.44 GPa and Young’s modulus of 125.08 GPa were achieved at a total drawing ratio of 11.7. Thus, this paper developed a self-reinforced preparation process for UHMWPE low-dimensional materials through multistage stretching of gel films with reserved shish crystals.