Analysis of a Single-Screw Extruder with a Grooved Plasticizing Barrel – Experimental Investigation

Abstract

In the field of extrusion, a very promising high performance extruder was introduced to the European plastics industry in 1999. This new type of single-screw extruder combines a grooved plasticizing barrel with a barrier screw. Compared to conventional extrusion systems, these extruders have by far a higher output and product quality among other advantages such as lower processing costs and lower energy consumption. In the past, both Newtonian and non-Newtonian models were developed to calculate and predict the melting rate along the flow channel. The aim of this paper is to present experimental investigations on the processes within the melting zone of a single-screw extruder with a grooved plasticizing barrel. To visualize the melting mechanisms, screw extraction experiments as well as dynamic pressure measurements were performed. By means of screw extraction experiments a solid bed was clearly identified only in the solid channel and a melt pool only in the melt channel. Analysis of the dynamic pressure signals also showed the same behavior and therefore allowed in-line characterization of the melting process. Thus, theoretical concepts about the melting mechanisms could be confirmed experimentally.

Fundamentals of Global Modeling for Polymer Extrusion

“…It was validated that this system shows more efficient melting, higher specific throughput, uniform pressure buildup, and lower processing costs compared to other high-performance extruders. Avila-Alfaro et al [93,94] presented the mathematical model for melting in the grooved plasticating unit, which was a revised version of the classic model of Tadmor with some improvements made by Vermeulen et al [77] and Pearson [78].…”

A novel melting model for polymer extrusion: Mechanically induced transition layer removal

“…[ 46 ] In addition, Kettemann et al could not confirm this assumption in their pullout experiments with a plasticizing unit with the cylinder divided axially into two halves. [ 48,49 ] This leads us to think that the melting mechanism in GPE is not completely explained. The present work proposes that not only the molten polymer is withdrawn toward the slots, but there is a high probability that part of the polymer close to changing from the solid to the molten state will be “pushed” by the screw flights into the grooves, thus achieving the considerable increase in the melting rate.…”