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      Vortical Fountain Flows in Plasticating Screws

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          Abstract

          Variances in polymers processed by single-screw extrusion are investigated. While vortical flows are well known in the fluids community and fountain flows are well known to be caused by the frozen layers in injection molding, our empirical evidence and process modeling suggests the presence of vortical fountain flows in the melt channels of plasticating screws adjacent to a slower-moving solids bed. The empirical evidence includes screw freezing experiments with cross-sections of processed high-impact polystyrene (HIPS) blended with varying colorants. Non-isothermal, non-Newtonian process simulations indicate that the underlying causality is increased flow conductance in the melt pool caused by higher temperatures and shear rates in the recirculating melt pool. The results indicate the development of persistent, coiled sheet morphologies in both general purpose and barrier screw designs. The behavior differs significantly from prior melting and plastication models with the net effect of broader residence time distributions. The process models guide potential strategies for the remediation of the processing variances as well as potential opportunities to achieve improved dispersion as well as complex micro and nanostructures in polymer processing.

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          Most cited references20

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          Rheology of non-Newtonian fluids: A new flow equation for pseudoplastic systems

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            On the no-slip boundary condition

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              Effects of polymer stresses on eddy structures in drag-reduced turbulent channel flow

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                Author and article information

                Journal
                Polymers (Basel)
                Polymers (Basel)
                polymers
                Polymers
                MDPI
                2073-4360
                26 July 2018
                August 2018
                : 10
                : 8
                Affiliations
                [1 ]Department of Plastics Engineering, University of Massachusetts Lowell, 220 Pawtucket St., Lowell, MA 01854, USA; Varun_Venoor@ 123456uml.edu
                [2 ]Fachbereich Maschinenbau und Kunststofftechnik, Hochschule Darmstadt, Gebäude C10, Schöfferstraße 3, Darmstadt 64295, Germany; clemens.m.grosskopf@ 123456stud.h-da.de
                Author notes
                [* ]Correspondence: david_kazmer@ 123456uml.edu ; Tel.: +1-978-934-2962
                Article
                polymers-10-00823
                10.3390/polym10080823
                6403816
                5ff3e7a1-5255-498a-b9b9-613a35380145
                © 2018 by the authors.

                Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ( http://creativecommons.org/licenses/by/4.0/).

                Categories
                Article

                single-screw extrusion,fountain flow,residence time distribution,polymer process simulation and modeling

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