Study of mixing efficiency in kneading discs of co‐rotating twin‐screw extruders

Co‐rotating twin‐screw extruders are widely used for compounding and blending in polymer processing. In a modular machine, the dominant elements determining dispersive mixing efficiency are the kneading discs. A fluid dynamics analysis package ‐ FIDAP, using the finite element method was implemented to simulate the 3‐D isothermal flow patterns in the kneading disc region of a Werner & Pfleiderer ZSK‐53 co‐rotating twin‐screw extruder. The kneading discs simulated are three‐lobe discs. The flow field characteristics relevant for dispersive mixing are shear stresses generated and elongational flow components. We compare these flow characteristics for the three‐lobe kneading discs of the ZSK‐53 with the two‐lobe discs of a ZSK‐30 machine. We also discuss the influence of processing parameters on the flow field mixing efficiency.