Extensional rheology and processing of polymeric materials / H. Münstedt in INTERNATIONAL POLYMER PROCESSING, Vol. XXXIII, N° 5 (11/2018)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XXXIII, N° 5 (11/2018) . - p. 594-618 Titre : Extensional rheology and processing of polymeric materials Type de document : texte imprimé Auteurs : H. Münstedt, Auteur Année de publication : 2018 Article en page(s) : p. 594-618 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Déformations (mécanique) Ecrouissage Filature Films plastiques Matières plastiques -- Soufflage Matières plastiques -- Thermoformage Moussants Rhéologie Index. décimale : 668.4 Plastiques, vinyles Résumé : Many processing operations of polymeric materials are dominated by extensional flow. In this paper the question is addressed in which way rheological data obtained from elongational laboratory experiments can be used to describe the material behavior in various processes. Particularly discussed is the uniformity of geometrical features of items with respect to the strain hardening of the polymeric materials, because uniformity is important for many end-use properties. Convincing correlations with extensional rheology could not be established for thermoforming experiments on polypropylene. However, for blown and drawn films it was found that the uniformity of thickness improved, if strain hardening was introduced. The bubble stability could be related to the melt strength of the sample. Furthermore, the influences of elasticity and strain hardening on the neck-in during drawing of films were elucidated. Moreover, it was shown in which way extensional rheology can be used to assess foaming. Note de contenu : - Main features of rheological properties in elongation - Relevance of strain hardening for the uniformity of stretched samples - Experimental methods - Biaxial deformations - Fiber spinning - Thermoforming - Film blowing - Film casting - Foaming DOI : 10.3139/217.3532 En ligne : https://www.degruyter.com/document/doi/10.3139/217.3532/pdf Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=31391 [article]

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Quantifying extrusion modification of LDPE with a microcompounder / T. Li in INTERNATIONAL POLYMER PROCESSING, Vol. XXVII, N° 1 (03/2012)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XXVII, N° 1 (03/2012) . - p. 91-97 Titre : Quantifying extrusion modification of LDPE with a microcompounder Type de document : texte imprimé Auteurs : T. Li, Auteur ; K. Kuklisin, Auteur ; J. Auger, Auteur ; J. Nielsen, Auteur ; W. Lin, Auteur Année de publication : 2012 Article en page(s) : p. 91-97 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Chromatographie sur gel Ecrouissage Malaxeurs et mélangeurs Matières plastiques -- Extrusion Poids moléculaires Polyéthylène basse densité Résonance magnétique nucléaire Rhéologie Index. décimale : 668.9 Polymères Résumé : Processibility of LDPE is known to be sensitive to processing history. Significant changes in processibility and product properties can occur through repeated extrusion without detectable changes in molecular weight and molecular weight distribution. Such changes of LDPE rheology are simulated with DSM micro-compounder and characterized with the small angle oscillatory tests and the SER uni-axial extensional flow with a K-BKZ analysis. Both the linear and the nonlinear rheology data suggest the major mechanism in the extrusion with the DSM micro-compounder is the reduction of the effects of long chain branching. The linear rheology analysis, along with GPC and NMR characterization confirms that the changes in the extrusion are not due to chemical crosslinking, though an increase in backbone molecular weight at extreme conditions is perceivable through the minor increase in molecular weight distribution, the increase in zero-shear viscosity and the decrease of melt index. The extensional rheology results, on the other hand, reveal the depression of the strain hardening with prolonged extrusion at 190 degree C or higher extrusion temperature. The stress growth data were evaluated with a K-BKZ constitutive with exponential damping function. The depression of strain hardening is well characterized with the strain hardening factor and the non-linear exponent beta as function of the extrusion conditions. The damping factor β is observed to be especially effective as the parameter to follow the depression of the strain hardening due to microcompounder extrusion. The microcompounder extrusion and the SER analysis with the KBKZ analysis prove to be a new useful tool for simulating the shear modification of the LDPE. Note de contenu : - LINEAR AND NON-LINEAR RHEOLOGICAL ANALYSES - EXPERIMENTAL : GPC - NMR - RESULTS AND DISCUSSION : Linear viscoelastic properties DOI : 10.3139/217.2421 En ligne : https://drive.google.com/file/d/1ILOBQQEN2Z6ZMbi9-ZmRaV-d3bo-Zd4B/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=13737 [article]

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