A dynamic melting model for a single‐screw extruder

Abstract

A new theoretical concept is given which provides an efficient and consistent method for predicting flow and heat transfer characteristics of the melting zone for a large singlescrew extruder. In contradistinction to previous theories, significant melt accumulation in the molten films as observed experimentally is considered, instead of postulating the melt accumulation in the "melt pool". The mathematical model has been obtained by the simultaneous solution of the momentum and energy equation of the melt flow and solid bed, allowing for the existence of the pressure gradient. The theory is supplemented by a numerical example which shows good agreement with experimental data obtained on a 90 mm extruder with polypropylene, where the down-channel pressure profile and the profile of the solid bed were taken as yardsticks for the melting process. For exact determination ofthe area for applicability of this theory, more experimental information is required.

Melting of polymer blends in single-screw extrusion - an experimental study

“…Experimental melting studies were initiated by Maddock in the fifties, yielding a qualitative phenomenological understanding of the underlying mechanisms [1]. Based on this evidence, Tadmor developed the corresponding mathematical description [2], which in fact formed the basis of subsequent more sophisticated analyses [3][4][5][6][7][8][9]. In his model, Tadmor assumes that the solid pellets are compacted and form a continuous bed, which is separated from the inner barrel wall by a thin melt film.…”

Mathematical model of a single-screw plasticating extruder

“…Examples of such refinements are Lovegrove's two-dimensional solids conveying zone model [25], models with solid-bed break-up theory given by Donovan [26], other models for the MZ given by Mondvai et al [27], Shapiro and Pearson [18], Edmonson and Fenner [28] and Lindt's special model for PP [29], and Dyer's three-dimensional model [30] for the MCZ. In spite of the simplifications in our model is was successfully used to design different types of single-screw plasticating extruders working with PP, PA, PET as well as their pigment master batches in man-made fibre production.…”

CFD-Simulation der Kunststoffplastifizierung in einem Extruder mit durchgehend genutetem Zylinder und Barriereschnecke

“…Weitere Modifikationen und/oder Erweiterungen des Modells folgten u. a. durch Donovan [18], Edmondson und Fenner [19], Lindt [20][21][22], Syrjälä [23] und Potente [24,25]. Diesen Ansätzen ist gemein, dass sie sich ausschließlich für Prozesse im Einschneckenextruder nutzen lassen und stets auf die Betrachtung eines abgewickelten Schneckenganges angewiesen sind.…”