Investigation of the effect of filler concentration on the flow characteristics of filled polyethylene melts / G. A. Campbell in INTERNATIONAL POLYMER PROCESSING, Vol. XXXIII, N° 5 (11/2018)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XXXIII, N° 5 (11/2018) . - p. 619-633 Titre : Investigation of the effect of filler concentration on the flow characteristics of filled polyethylene melts Type de document : texte imprimé Auteurs : G. A. Campbell, Auteur ; M. D. Wetzel, Auteur Année de publication : 2018 Article en page(s) : p. 619-633 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Charges (matériaux) Dispersions et suspensions Fluides newtoniens Matières plastiques -- Extrusion Matières plastiques -- Moulage par injection Polyéthylène Rhéologie Index. décimale : 668.4 Plastiques, vinyles Résumé : All polymeric slurries that have a high concentration of filler are shear thinning. Shear thinning is an important characteristic of polymers, filled and unfilled, because it enables an increase in the throughput, shear rate in a die or an injection molding system without having to use substantially more power to increase the flow rate. Newtonian fluid-based slurries show an increase in shear thinning as the concentration of "filler" increases above the percolation threshold. As particle maximum packing concentration is approached the slurries begin to approach a perfect pseudoplastic fluid. In some cases, the shear thinning characteristics of a filled polymer do not increase substantially as the filler loading is increased. This is a quite different response that is newtonian fluid-based slurry. Therefore, it is important to understand the materials engineering interactions that control shear thinning so that process flow models can better predict the performance of filled polymer system. Highly filled polymers can have processing issues, including high screw shaft torque, energy consumption, die pressure and melt temperature rise. Previous theoretical developments and experimental evaluations of highly filled polymer melts showed that the rheology can be effectively described with a percolation model. In this work, capillary rheometer measurments using several low-density polyethylene resins, calcium carbonate and titanium dioxyde fillers are reported using percolation theory concepts. The theoretical treatment of the rheology as a particulate percolating system with power-law behavior is used to analysed capillary rheometer data. The observed effects of resin molecular weight, filler type and size on rheology are described. Engineers that design and debottleneck polymer processes need to utilize the polymer viscosity at the minimum process shear rate to determine the smallest motor that will allow the process to run ; in addition, the shear thinning characteristics of the polypmer are used to indicate how much increased production may be possible with a given motor size. Thus, some examples of expected effects on melt processing are also presented. Note de contenu : - POWER LAW THEORY DEVELOPMENT : Power law index, n - EXPERIMENTAL PROCEDURES : Application of the power law theory to newtonian fluid-based slurries - APPLICATION OF THEORY TO FILLED POLYMER MELTS : Implications for extrusion and molding processes DOI : 10.3139/217.3571 En ligne : https://www.degruyter.com/document/doi/10.3139/217.3571/pdf Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=31392 [article]

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