Factors Affecting Productivity and Quality in the Extrusion of Polyvinylchloride Powder

Abstract

Microscope examination of material from a single screw extruder screw channel following removal from the extruder barrel showed that the fusion mechanism and fusion rate depended on the lubricants used. One of two different fusion mechanisms occurred depending on the formulation, The "rear of the channel fusion model" produced rapid fusion and promoted mixing, while the 'forward fusion model" resulted in incomplete fusion and the presence of unfused PVC particles in the extrudate. Rate of fusion depended on the level of the various additives. Thus increasing the level of incompatible lubricant decreased the foster rate, while incorporation of process aids, impact modifiers and filler increased the fusion rate. Output rate was dependent on the rate of fusion with the result that increasing the fusion rate decreased the output rate. This means that factors causing fusion rate variations will also result in output rate fluctuations. For maximum thermal stability an optimum fusion rate exists as earlier fusion results in overheating while late or incomplete fusion results. in late or inadequate incorporation of stabiliser. The existance of two possible mechanisms explains why, following (for economic reasons) the superseding of granule extrusion by direct powder extrusion, British extrusion practice favoured the imported twin screw extruder, whereas United States practice was to continue with the cheaper rugged single screw machine.

Divisions: College of Engineering & Physical Sciences > School of Infrastructure and Sustainable Engineering > Chemical Engineering & Applied Chemistry
Additional Information: Copyright © Gale, 1972. G.M. Gale asserts their moral right to be identified as the author of this thesis. This copy of the thesis has been supplied on condition that anyone who consults it is understood to recognise that its copyright rests with its author and that no quotation from the thesis and no information derived from it may be published without appropriate permission or acknowledgement. If you have discovered material in Aston Publications Explorer which is unlawful e.g. breaches copyright, (either yours or that of a third party) or any other law, including but not limited to those relating to patent, trademark, confidentiality, data protection, obscenity, defamation, libel, then please read our Takedown Policy and contact the service immediately.
Institution: Aston University
Uncontrolled Keywords: productivity and quality,extrusion of polyvinylchloride powder
Last Modified: 08 Dec 2023 08:02
Date Deposited: 28 Oct 2019 15:37
Completed Date: 1972
Authors: Gale, George M.

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