New Wave-Screw Concepts in High-Speed Extruder.

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Research Project Contents:Single-screw extruders are indisputably the most important machines in the polymer processing industry. During plasticating extrusion, polymer is fed to the extruder in the solid-state and the material is melted as it is conveyed by the rotating extruder screw from the feed port to the die. Based on the economic framework, the primary objective of machine manufacturers is to increase the output capacity while guaranteeing high melt quality. Meeting these demands requires proper screw design and thus a thorough understanding of the transport phenomena governing the extrusion process. Focusing on solid bed breaking screw concepts, this research project will investigate wave- and energy-transfer-sections in detail placing special emphasis on their application in the melting zone of high-speed single-screw extruders. In order to take advantage of their great potential to combine both high output rates and excellent melt quality, new design strategies based on mathematical-physical models will be developed and validated by experimental studies carried out on fast running single-screw extruders. This will yield a sustainable contribution for the development of high-speed extrusion concepts in combination with solid bed breaking screw sections.Hypothesis:The research work will provide mathematical-physical process models needed to optimize wave- and energy-transfer-sections in the melting zone of high-speed single-screw extruders. This will help to meet the high demands made on the single-screw extruder regarding output capacity and melt quality.Methods:Experimental studies will be carried out on both a novel screw simulator allowing the detailed analysis of the melting process in solid bed breaking flow channels and on a conventional as well as a grooved feed high-speed single-screw extruder. To extend existing process models, analytical as well as numerical methods will be applied comprising the network theory and the finite volume method in particular. Innovation and novelty:The few scientific papers dealing with the above mentioned topic still leave many questions unanswered and show that the contents of this proposal are highly relevant. Previous studies have proven that increased output rates caused by an early breaking of the solid bed in high-speed extrusion can be combined with the high requirements in terms of melt quality. Especially the application of wave- and energy-transfer-sections in the melting zone is of high interest, as these zones show the potential to induce solid bed breaking. However, as wave- or energy-transfer-zones are usually found in the melt conveying zone, their application in the melting zone requires new design strategies based on mathematical-physical process models.