Influence Of Screw Configurations On Mixing Effect Of Polymer Compounding In Co-Rotating Twin Screw Extruder

In the polymer compounding process, screw configurations are important factor influencing the mixing effect of the polymer blends in co-rotating twin screw extruder.In this paper, applied the professional package of Computational Fluid Dynamics, POLYFLOW, the flow field of different screw configurations for three-dimensional isothermal Non-Newtonian model in intermeshing co-rotating twin screw extruder were simulated. The screw elements included SE20/120, KB60/120, KB90/120, KB120/120, S, TME, FTX, NI-MPE. Shear-stress profile, residence time distribution and backflow rate were obtained. The mixing ability of different screw configurations was compared. KB120/120 had the greatest dispersive mixing ability for its powerful shear stress effect. KB60/120, KB90/120 and SE20/120 also had significant effect on dispersive mixing. For distributive mixing ability, KB120/120 and FTX showed excellent performance on distributive mixing ability, because they had the greatest backflow and the widest distance between inflexions of RTD curve respectively. The other new type screw elements also had good distributive mixing ability.The accuracy of simulation results were verified by experimental studies. In addition, the influence of screw configurations on binary immiscible blend was got further investigation. Besides screw elements employed in simulation, KB30/120, KB150/120, and ZME were added in experiment study. These screw configurations were located at either the melting section or the melt conveying section of co-rotating twin screw extruder. The results showed that: kneading block elements had significant effect on dispersive mixing ability, which was more suitable for being located at melting section than melt conveying section of co-rotating twin screw extruder. S element provided good performance on distributive mixing. In addition, because of its structure feature which resulted in elongational flow enhanced the dispersive mixing ability, so it is suitable for being located at melting section. FTX element, TME or NI-MPE had significant effect on distributive mixing ability. They were located at melt conveying section of co-rotating twin screw extruder would obtain homogenization products.