Modeling and estimation of the pressure and temperature dependent bulk density of polymers / Christian Kneidinger in INTERNATIONAL POLYMER PROCESSING, Vol. XXXV, N° 1 (03/2020)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XXXV, N° 1 (03/2020) . - p. 70-82 Titre : Modeling and estimation of the pressure and temperature dependent bulk density of polymers Type de document : texte imprimé Auteurs : Christian Kneidinger, Auteur ; M. Längauer, Auteur ; Gernot Zitzenbacher, Auteur ; S. Schuschnigg, Auteur ; Jürgen Miethlinger, Auteur Année de publication : 2020 Article en page(s) : p. 70-82 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Extrudeuse monovis Masse volumique Mesure Modèles mathématiques Polymères Pression Index. décimale : 668.4 Plastiques, vinyles Résumé : The bulk density of polymers is a crucial factor for the throughput and the pressure build-up of single screw plasticating units. It depends not only on the density of the polymeric material itself, but also on the geometry of the single pellets, on the dimensions of the screw channel and, furthermore, on the temperature and the pressure. A review of the existing models shows that there is potential for improvement, as their applicability is restricted. It is difficult to obtain model parameters, as they can only be determined by experiment, but there are only a few devices which enable temperature- and pressure-dependent bulk density to be measured. Furthermore, these devices are not standardized. This work presents a new model which can be used to calculate the bulk density as a function of pressure and temperature and an adapted approach that considers the dimensions of the single pellets and the screw channel. The model is verified by both, new data derived from experiments and data from the literature. Compared to existing models, this new model fits the experimental data better, requires fewer parameters and shows much better extrapolation behavior as well as a continuous changeover behavior at the melting temperature. Another big advantage of the new model compared to the existing ones is that the model parameters of this new model can be estimated from the stress at yield and from the melting temperature. This enables a rough estimation of the pressure and temperature dependent bulk density without having to measure it. Note de contenu : - INTRODUCTION : Measurement of the bulk density - Existing models - Evaluation of the existing models - PROPOSED MODEL : Material density - Adjustable approach - Simplified approach - Combined approach - Modification by implementation of the volumetric transition temperature - Modifications considering the temperature dependence of the bulk density at zero pressure - Consideration of the screw channel geometry - Benefits of the new model compared to the existing models - Parameter fitting - MATERIALS USED - RESULTS AND DISCUSSION - ESTIMATING MODEL PARAMETERS FROM MATERIAL PROPERTIES DOI : https://doi.org/10.3139/217.3876 En ligne : https://drive.google.com/file/d/1jH3kB_e72-_OymLxouI82g5CYVTN2VzK/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=33780 [article]

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Verifying the melting behavior in single-screw plasticization units using a novel simulation model and experimental method / M. Aigner in INTERNATIONAL POLYMER PROCESSING, Vol. XXIX, N° 5 (11/2014)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XXIX, N° 5 (11/2014) . - p. 624-634 Titre : Verifying the melting behavior in single-screw plasticization units using a novel simulation model and experimental method Type de document : texte imprimé Auteurs : M. Aigner, Auteur ; Bernhard Praher, Auteur ; Christian Kneidinger, Auteur ; Jürgen Miethlinger, Auteur ; Georg Steinbichler, Auteur Année de publication : 2014 Article en page(s) : p. 624-634 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Analyse thermique Extrusion filage Mesure Modèles mathématiques Plastification Polymères -- Fusion Simulation, Méthode de Ultrasons Index. décimale : 668.9 Polymères Résumé : We report on the development of a novel non-invasive ultrasonic measurement system for determining the melting behavior in a single-screw plasticization unit (35/22D) and on a modified drag-induced melt removal model that builds upon that by Tadmor and Gogos (2006). The solid bed to melt pool ratio is quantified using a non-invasive ultrasonic system based on reflection measurements. Automated analysis of the reflected pulses – measured at different axial positions along the barrel – allows the melting process to be monitored online. Our analysis of the delay section incorporates viscous dissipation into Tadmor's drag-induced melt removal model. We link temperature profile and melt film thickness via differential equations and consider viscous dissipation. By segmenting the delay section in the axial direction, the temperature dependency of the thermo-physical material properties is also considered. Using the melting behavior measured for different materials, we verified the mathematical model. Additionally, the effect of reduced screw length on the plasticization process, important for the injection molding process, was investigated. Note de contenu : - EXPERIMENTAL : 1. Materials - 2. Thermal Analysis - 3. Computational Schemes Used in Simulation - EXPERIMENTAL SETUP - RESULTS AND DISCUSSION : 1. Simulation Results - 2. Comparison between Simulation and Experimental Results DOI : 10.3139/217.2949 En ligne : https://drive.google.com/file/d/1UGKUVSLn6yaqPAf5dRtBqH361NnGvTsW/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=22242 [article]

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