Simulation And Experimental Study On The Process Of Melt Extrusion Of Ultra High Molecular Weight Polyethylene

Ultra-high molecular weight polyethylene(UHMWPE)fiber has high strength and toughness,and has very good chemical corrosion resistance,wear resistance and bending resistance.It is widely used in the production of ropes,military equipment and aerospace products.In recent years,gel spinning method is mainly used to produce UHMWPE fiber in the industry,however,as we all know,it has so many disadvantages,for example complicated in preparation process,requiring a large amount of solvent,increased production cost and caused environmental pollution.Compared with gel spinning method,melt spinning method has many advantages,such as simple preparation process,high yield,low cost and no pollution.Therefore,it has attracted more and more scholars' attention and research recently.The as-spun filaments refers to a filament that has been subjected to extrusion winding but has not been subjected to secondary drawing treatment during melt spinning.The surface quality and mechanical properties of the as-spun filaments will directly affect the properties of the fiber.The UHMWPE/HDPE/SiO2 blends are subjected to strong shearing and stretching through the orifice of the spinneret.During this melt extrusion process,the velocity field,shear rate field and pressure field of the melt in the converging flow channel will be changed,and different degrees of extrusion distortion will be underwent after the extrusion die under different spinneret structure and process parameters.These will have an impact on the performance of the as-spun filaments.The main works are as follows(1)The flow state of UHMWPE/HDPE/SiO2 blend was numerically calculated by using POLYFLOW software,the distribution of velocity field,shear rate field and pressure field was analyzed and the extrusion swell ratio of the as-spun filaments was calculated in different structure of the spinneret flow channel(convergence angle,aspect ratio).Moreover,the structural parameters of the spinneret of the spinning machine were optimized according to the simulation results;(2)The flow state of UHMWPE/HDPE/SiO2 blend was numerically calculated by using POLYFLOW software,the distribution of velocity field,shear rate field and pressure field was analyzed and the extrusion swell ratio of the as-spun filaments was calculated in different process parameters(mold processing temperature,metering pump speed).Moreover,the process parameters during processing were optimized according to the simulation results.(3)The process parameters of melt extrusion of UHMWPE/HDPE/SiO2 blend was studied by using experimental methods.In this process,the as-spun filaments was prepared and the average tensile strength,elongation at break,and extrusion swell ratio were tested under different head processing temperatures,different metering pump speeds,different cooling methods,and different winding speeds.In order to verify the numerical simulation results,comparison between the experimental results and the simulation results were made,and a reasonable process route was established to obtain the as-spun filaments with better quality.