Modeling of Melt Conveying in a Novel Screw-Nested Extruder

Abstract

Abstract A novel screw-nested extruder is fabricated, which consists of double extrusion systems. The inner screw couples with one inner barrel, whose outer configuration acts as the screw for the outer barrel. The nested screw extrusion systems can co-extrude when the inner barrel/outer screw rotates. Each extrusion system can also work independently as one general extruder. A new mathematical model of an isothermal Newtonian flow is developed to describe the melt flow in the extruder. The analytical solutions of flow rate are well in agreement with the Campbell's experimental data for screw drag flow, screw flight displacement flow and barrel drag flow when the boundary conditions are obtained for the special cases in which the screw core, screw flight and the barrel rotate independently or in pairs. This can not be explained by conventional parallel-plate models. Further, the model is also well used to analyze the melt flow in the inner extrusion system of the novel nested screw extruder.