Study On Rheological Properties And Melt Spinning Of Modified Uhmwpe Material

Ultra-high molecular weight polyethylene(UHMWPE)fiber is a kind of special fiber with high strength,and its products are widely used in many fields.At present,the main way to prepare UHMWPE fiber in the world is gel spinning(using ten naphthalene,mineral oil and other solvents),which has large energy consumption and environmental problems,and has high production cost.Melt spinning process does not require solvent or extractant,and the preparation process can be simplified with shortened production process,reduced cost and no pollution,which is in line with the advocacy of green technology.Therefore,the preparation of UHMWPE fibers by melt spinning process can realize low-cost production of high-strength UHMWPE fibers,thus expanding the application scope of UHMWPE fibers in the civil field.Due to the high molecular weight of UHMWPE and the entanglement of large molecular chains,the extrusion distortion of as-spun filament has always been a key problem restricting the further development of melt spinning process,which will lead to the failure of subsequent hot drawn process for the prepared as-spun filament,thus limiting the improvement of the UHMWPE fiber strength.In this study,UHMWPE/HDPE/SiO2 modified spinning material system was developed to improve the spinnability of raw materials,and solve the melt fracture problem in the extrusion process of as-spun filament.The melt spinning process was optimized and UHMWPE/HDPE/SiO2 blend fibers with good mechanical properties were successfully prepared.The rheological properties and distortion mechanism of UHMWPE/HDPE/SiO2 modified system were studied.The effect of spinning process on the structure and mechanical properties of nanocomposite fibers was analyzed.The key role of nanoparticles in the microstructural evolution of blend as-spun filaments and blend fibers was revealed.The main research work is as follows:1.The applicable properties for UHMWPE,UHMWPE/HDPE and UHMWPE/HDPE/SiO2 blend systems in capillary extrusion rheological behavior,drawing continuity and crystallization behavior under thermal and stress field were analyzed and compared.The modified blend material system adapted to the characteristic of melt spinning process was obtained.2.The rheological behavior of UHMWPE/HDPE/SiO2 nanocomposites was studied.The effect mechanism of modified nano-particles on the distortion rupture of the blends during extrusion was analyzed.The important relationship between the interface conditions of nano-SiO2 dispersed phase and PE matrix and the rheological behavior of the blends was discussed.The origin of critical shear rate and critical shear stress of flow instabilities were further discussed.3.The mechanical properties of nanocomposite fibers were analyzed.The effect mechanism of modified nano-particles on the orientation of molecular chains in as-spun filaments under flow shear was expounded.The evolution process of crystal structure destruction,slip and reorganization in the thermal and stress fields of as-spun filaments during hot drawn process was revealed.The influence of modified nano-particles on the microstructure of as-spun filaments and fibers was analyzed.4.The effects of spinning process parameters such as filament cooling method,spinning temperature and hot drawn temperature on the structure and mechanical properties of nanocomposite fibers were compared.The response mechanism of nanocomposite to the spinning process in the cooling solidification crystallization stage and the structural deformation stage of hot drawn process was further revealed.The melt spinning process was further optimized.