Extrusion foaming of linear and branched polypropylenes - input of the thermomechanical analysis of pressure drop in the die / Carlos Sandino in INTERNATIONAL POLYMER PROCESSING, Vol. 37, N° 4 (2022)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. 37, N° 4 (2022) . - p. 383-395 Titre : Extrusion foaming of linear and branched polypropylenes - input of the thermomechanical analysis of pressure drop in the die Type de document : texte imprimé Auteurs : Carlos Sandino, Auteur ; Edith Peuvrel-Disdier, Auteur ; Jean-François Agassant, Auteur ; Patrice Laure, Auteur ; Séverine A. E. Boyer, Auteur ; Geoffrey Hibert, Auteur ; Yves Trolez, Auteur Année de publication : 2022 Article en page(s) : p. 383-395 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Analyse thermomécanique Caractérisation Extrusion moussage Mousses plastiques -- Extrusion Polypropylène Index. décimale : 668.4 Plastiques, vinyles Résumé : This paper aims at a better understanding of the polypropylene (PP) physical extrusion foaming process with the objective of obtaining the lowest possible foam density. Two branched PPs were compared to the corresponding linear ones. Their shear and elongation viscosities were measured as well as their crystalline properties. Trials were conducted in a single screw extruder equipped with a gear pump and a static mixer cooler to adjust the melt temperature at the final die. The effect of decreasing this temperature on the PP foamability and on the pressure drop in the die was analyzed. The foam density of branched PPs varies from high to low values while decreasing the foaming temperature. In the same processing conditions, the foam density of linear PPs does not decrease so much, as already evidenced in the literature. The foamability transition coincides with an increase of the pressure drop in the die. The originality of the work lies in the thermomechanical analysis of the polymer flow in the die which allows the identification of the relevant physical phenomena for a good foamability. The comparison of the experimental pressure drops in the die and the computed ones with the identified purely viscous behavior points out the influence of the foaming temperature and of the PP structure. At high foaming temperature the discrepancy between experimental measurements and the computed pressure drops remains limited. It increases when decreasing the foaming temperature, but the mismatch is much more important for branched PPs than for linear ones. This difference is analyzed as a combination of the activation energy of the viscosity, the elongational viscosity in the convergent geometry of the die which is much more important for branched PPs than for linear ones, and the onset of crystallization which occurs at higher temperature for branched PPs than for linear PPs. Note de contenu : - CHARACTERIZATION OF THE LINEAR AND BRANCHED POLYPROPYLENES - FOAMING PROCESSES - EXPERIMENTAL SET UP : Processing conditions - Influence of the processing conditions on the foam density - THERMOMECHANICAL ANALYSIS OF THE FOAMING PROCESS DOI : https://doi.org/10.1515/ipp-2022-0025 En ligne : https://drive.google.com/file/d/1c_FH7lX3s_oRI2pmxBYZ3tXm5W93fgYt/view?usp=shari [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=37914 [article]

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