A Model for Single-screw Plasticating Extruders

Abstract

Abstract A mathematical model has been developed to describe the steady-state behavior of single-screw plasticating extruders. The model is capable of predicting the solid bed profile, pressure, and polymer temperature profiles along the screw channel. The model is based on concepts developed by Tadmor and Klein [1], but a modified model for plastication rate is proposed and the pressure profile is calculated using a unidirectional power-law flow model, in which correction factors for flight walls, curvature, and varying channel height have been incorporated. A finite difference technique (Crank-Nichols on method) is used to compute the polymer temperature profile. The overall extruder performance (pressure, temperature and solid bed profiles) is obtained with short computer times on a personal computer (typically one minute on IBM AT). A series of menus and graphics allow for selective simulation and rapid visualization of effects of key parameters, making the model attractive for screw design and optimization of operating conditions. The predictions are in good agreement with experimental data obtained for a polyethylene on a 45 mm diameter screw extruder.