Efficient self-reinforcement technology and mechanism for ultra-high molecular weight polyethylene based on powder solid-state extension

Abstract

Ultra-high molecular weight polyethylene (UHMWPE) is a semicrystalline polymer with an ultra-long molecular chain structure, so its melt viscosity is extremely high, making its thermoplastic forming quite challenging. To address this issue, in this study, a powder solid-state extension (PSSE) technology is proposed in which commercial UHMWPE nascent powder is uniaxially extended in the solid state, followed by low-temperature sintering, and a highly self-reinforced material with a tensile strength of 297.4 MPa and modulus of 5.79 GPa is prepared. Further, wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) combined with entropy-driven theory are used to examine the structural evolution process of amorphous and crystalline phases under different strains in the PSSE process, and a solid-phase induced transformation model of the shish-kebab structure is established. Overall, the proposed PSSE technique opens a new processing route for UHMWPE and provides useful insights on the structural evolution of discrete particles during the self-reinforcement process.