Distributive mixing characteristics of a Dulmage-type screw for a single-screw extruder: Experimental and numerical evaluation

Abstract

The mixing characteristics of a Dulmage-type screw, a kind of distributive mixing element, in single-screw extrusion were investigated. To evaluate the mixing ability, a melt-mixing extrusion experiment diluting a masterbatch with its base polymer and a numerical polymer melt flow simulation were performed. The experimental and simulation results revealed that the screw mixing performance oscillates with respect to N/Q, where N and Q are the screw rotation speed and the mass flow rate, respectively. The simulation results demonstrated that the screw mixing progresses by repeating the circumferential mixing in the ring zones and the radial redistribution in the fin zone slots. Based on these mixing kinetics, the number of swirling movements in the fin zone slots that determines the radial redistribution was found to govern the N/Q dependence of the global mixing. This study provides an essential guide for optimizing Dulmage-type screw mixing operations and Dulmage-type screw structure improvements.

Keywords

• Polymer processing
• Single-screw extruder
• Extrusion experiment
• Numerical simulation
• Distributive mixing