The Influence Of Intermeshing Co-Rotating Twin Screw Configurations On The Degradation Of Polypropylene

Formula, operation conditions and screw configurations are major factors influencing the degradation of the polypropylene(PP) in granulation process by intermeshing co-rotating twin screw extruder.In this paper, the flow fields of different screw configurations for three-dimensional isothermal Non-Newtonian model in intermeshing co-rotating twin screw extruder were simulated by the professional package, POLYFLOW. The screw elements included kneading block with straggle angle of 30°,90°,150°, SME, TME, NI-MPE. Pressure profile, shear stress profile, weighted average shear stress, backflow rate and RTD were obtained. It has been found that kneading block had the better dispersive mixing ability. The new type screw elements had fine distributive mixing performance.The experimental results of influence of operation conditions on the PP degradation showed that, with the feeding rate increasing, the degradation was weakened; with the screw revolution speed increasing, the degradation was increased. To multiple processing, the degradation was intensified, the tensile strength and impact strength decreased.The experimental results of influence of screw configurations on the PP degradation showed that, with the stagger angle of kneading disc increasing, the degradation was increased and the mechanical properties gradually decreased; with the thickness of kneading disc increasing, the degradation increased and the mechanical properties gradually decreased. The middle part of NI-MPE is non-intermeshing element, so the degradation was weaker due to the small shear effect. TME and SME had intensive degradation for the powerful shear stress than NI-MPE.The compare of theoretical results and experimental results indicated that, with dispersive mixing performance and distributive mixing performance increasing, the degradation of PP increased.