Study On Polymer Particles Conveying Behavior In Single Screw Extruder

In this paper the research on the conveying behavior of polymer particles in single screw extruder was conducted by the discrete element method (DEM) based on the programming platform of the PFC (Particle Flow Code). By using DEM, materials were seen as discrete particles in extruder feeding section. Collision, extrusion and sliding between material particles affected on materials forward conveying. Unlike the conveying behavior of materials using plug flowing theory, non-plug flowing theory was more consistent with the actual situation.The contact model of discrete element method was researched. The spring-damping model and adhesion model considering adhesion force between particles were compared and discussed. The value of the coefficient of restitution about spring-damping model was abtained by experiment. The effect of adhesion force on the extrusion process was discussed by using the nonlinear spring-damping model without considering the adhesion force and the adhesion model considering the adhesion force to simulate the extrusion process. Results showed that extrusion production decreased slightly when considering the adhesion force. In addition, the material filling rates, the coordination number and the pressure in the extruder increased.The extrusion process of materials in the extruder feeding section was simulated by using nonlinear spring-damping model. The relationship between materials’ density and pressure inside the cylinder was simulated. Compared to the experiment, the discrete element method for pressure prediction is reliable. The relationship between screw speed and extrusion production was simulated. Compared to the experiment, the discrete element method for extrusion production prediction is reliable. The extrusion production increased and formation pressure decreased as the extruder end opening. Keeping the same opening, the influence of friction coefficient on extrusion production and extrusion pressure was studied. The extrusion productions of different materials are different in the extruder. Changing the screw speed, the effect of screw speed on extrusion production and pressure was studied. It found that the extrusion speed of materials in the screw pushing was faster than screw back with the tracer particles. The study found the effect of rotational speed on extruder feeding. Rotational speed may lead to extrusion instability. Keeping the same extruder speed, the materials speed decreased along the extrusion direction. The greater extruder’s speed is the greater material’s speed. The motion trajectory of the material in the extruder was studied.