Dissolving of Ultra-high Molecular Weight Polyethylene Assisted Through Supercritical Carbon Dioxide to Enhance the Mechanical Properties of Fibers

The molecular weight of ultra-high molecular weight polyethylene (UHMWPE) fibers is severely decreased compared with raw materials due to high temperature and strong shearing in the dissolving process. In this study, we reported a novel method to assist the dissolving of UHMWPE in paraffin oil without severe degradation in order to improve the tensile strength of resultant fibers. UHMWPE fibers with relatively high molecular weight and more excellent disentanglement effect were prepared by gel-spinning with UHMWPE suspension treated with supercritical carbon dioxide (SC-CO2). The dynamic thermomechanical, mechanical and crystalline properties of UHMWPE extracted fibers and drawn fibers were researched comprehensively. UHMWPE extracted fibers obtained after SC-CO2 treatment display a higher molecular weight. More importantly, it is clear that the disentanglement of UHMWPE gel fibers gained by processing SC-CO2 has been significantly promoted compared with that without SC-CO2 treatment from dynamic thermomechanical and rheological results, which could also be demonstrated from the cross-sectional morphology of UHMWPE extracted fibers. Furthermore, the tensile strength of UHMWPE fibers prepared through SC-CO2 treating is able to attain 30.11 cN/dtex, increased by 10.3% in comparison to UHMWPE fibers gained without assistance of SC-CO2. Beyond that, the thermal behavior and crystallization performance of UHMWPE extracted fibers and drawn fibers acquired by way of SC-CO2 treatment have also been enhanced.