Twin-screw Gel Spinning Process And Properties Of Ultra-high Molecular Weight Polyethylene

Ultra high molecular weight polyethylene has a molecular weight of 1~5 million.As the fiber with high strength and high modulus,UHMWPE fiber has been widely used in the fields of biology and medical treatment,safety protection,aerospace and ocean engineering and so on.However,the mechanical properties and electrical properties of the fiber is significantly lower than the theoretical values because of the limited spinning technological level.The material ratio,process conditions and screw configuration determine the performance of the blend extrusion material.Therefore,it is important to optimize the extrusion process of UHMWPE fiber.The UHMWPE powder / oil was extruded and the UHMWPE gel was obtained using the HT-30 twin screw extruder.The UHMWPE fiber was obtained by gel spinning.Firstly,the UHMWPE fiber was prepared by twin-screw extruder.The effects of UHMWPE concentration,screw speed and barrel temperature on the initial residence time and mechanical properties of the fiber were investigated through orthogonal experiment analysis and single factor experiment analysis,and the optimum technological conditions were found.The results show that the mechanical properties of the fiber are optimal when solution concentration of 6%,screw speed range of 13~16rpm and barrel temperature of 160oC.Secondly,the rheological properties of UHMWPE gel and UHMWPE powder / oil mixed solution were tested using the rotational rheometer.The rheological behavior of UHMWPE gel and UHMWPE powder / oil mixture under different temperature and concentration was analyzed.The viscosity values under different conditions were obtained,and the difference between them was compared.It is found that the viscosity of UHMWPE flake gel is smaller than that of UHMWPE powder / oil mixture.Both viscosities increase with the increasing solution concentration and decrease with the increasing temperature.The rheological behavior research of UHMWPE gels can provide guidance for the selection of temperature and concentration in the spinning process and the subsequent simulation.Finally,the extrusion process of screw extruder was simulated by CFD simulation software.The velocity field in the twin screw extruder and the minimum velocity at cross section were obtained and compared with the residence time in experimental results.It is found that the gel velocity at the screw feeding section and the melting section increases with the increasing screw speed.The velocity of the gel at the extrusion section increases first while decreases with the increasing screw speed.The simulation agrees well with the experimental results.The temperature(85~95oC)of the screw has little effect on the material speed at the feeding section while the influence of temperature on the material velocity at melting section becomes larger.With the increase of temperature,the gel velocity increases first then decreases.With the increase of the screw temperature,the speed of the gel decreases greatly,and the temperature of the screw has the greatest influence on it at the exhaustion section.