Pressure Variation during Interfacial Instability in the Coextrusion of Low Density Polyethylene Melts
| Autor: | Philip D. Coates, Michael Martyn |
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| Rok vydání: | 2013 |
| Předmět: |
Engineering drawing
business.product_category Materials science Polymers and Plastics General Chemical Engineering Plastics extrusion Die swell Instability Industrial and Manufacturing Engineering Low-density polyethylene Materials Chemistry Die (manufacturing) Composite material Elasticity (economics) business Layer (electronics) Melt flow index |
| Zdroj: | International Polymer Processing. 28:516-527 |
| ISSN: | 2195-8602 0930-777X |
| DOI: | 10.3139/217.2786 |
| Popis: | Pressure variation during the coextrusion of two low density polyethylene melts was investigated. Melt streams were delivered to a die from two separate extruders to converge in a 30°° geometry to form a two layer extrudate. Melt flow in the confluent region and die land to the die exit was observed through side windows of a visualisation cell. Stream velocity ratio was varied by control of extruder screw speeds. Layer thickness ratios producing wave type interfacial instability were quantified for each melt coextruded on itself and for the combined melts. Stream pressures and screw speeds were monitored and analysed. Wave type interfacial instability was present during the processing of the melts at specific, repeatable, stream layer ratios. Increased melt elasticity appeared to promote this type of instability. Analysis of process data indicates little correlation between perturbations in extruder screw speeds and stream pressures. The analysis did however show covariance between the individual stream pressure perturbations. Interestingly there was significant correlation even when interfacial instability was not present. We conclude that naturally occurring variation in extruder screw speeds do not perturb stream pressures and, more importantly, natural perturbations in stream pressures do not promote interfacial instability. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
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