Effect of co-rotating twin screw and counter-rotating twin screw on polylactic acid extrusion process
The influences of the co-rotating twin screw and counter-rotating twin screw on the extrusion process of polylactic acid and the properties of the extrudate were discussed.The end curves of the co-rotating twin screw and the counter-rotating twin screw were established with the relative motion method under the same structural parameters.The three-dimensional model generat-ed by the end curve was meshed,and the mesh model was imported into Polyflow software to set boundary conditions and add tracer particles for simulation analysis.The Fieldview post-processing software was used to visually analyze the physical field in the simu-lation data,and the trajectory of the tracer particles in the flow channel was studied.The results show that the pressure in the flow channel of the co-rotating twin screw is relatively stable in the process of extrusion,and the local high pressure appears in the counter-rotating twin screw.In the process of poly-lactic acid extrusion in the co-rotating twin screw,the tracer particle retention time is shorter,the distribution index and separation scale are smaller,that is,the distribution mixing ability is stronger,and the extrusion material has high tensile strength.In the process of extrusion in the counter-rotating twin screw,the material is subjected to greater shear and tensile effects,and the particles experiencing the maximum shear stress account for more,that is,the dispersion mixing ability is stronger,and the impact strength of the extrusion material is higher,the viscosity is lower.It can be seen from the results that the co-rotating twin screw can provide relatively stable and efficient extrusion process,extrusion process is fast,distribu-tion and mixing is more uniform,and the counter-rotating twin screw has stronger pressure building capacity,shear capacity and dispersion and mixing capacity,which can enhance the product quality of extruded materials.
twin screwco-rotatingcounter-rotatingfinite element analysistracer particle
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