Prediction of Flow of a Melted Plastic Through a Screw Extruder

Abstract

A theory is formulated for predicting the variation in average pressure and the rise in average temperature in molten plastic along the axis of a screw extruder. The mathematical model is for a wide, shallow channel of negligible curvature and includes both down and cross channel components of the shearing stress which are related to strain rates by a generalized Rabinowitsch constitutive equation for a non-Newtonian Liquid. Twenty experiments were performed in a commercial screw extruder in which pressures and temperature changes in the plastic were measured. Experimental correlation with theory is very good for pressure distribution along the screw axis and fair for temperature rises of at least 50 deg F.