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Extrusion coating with metallocene-catalysed polyethylenes / N. Toft in INTERNATIONAL POLYMER PROCESSING, Vol. XVII, N° 3 (09/2002)
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Titre : Extrusion coating with metallocene-catalysed polyethylenes Type de document : texte imprimé Auteurs : N. Toft, Auteur ; M. Rigdahl, Auteur Année de publication : 2002 Article en page(s) : p. 244-253 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 668.9 Polymères Résumé : During recent years, the interest in metallocene-catalysed polyethylenes has been steadily increasing. These polymers are generally characterised by a narrow molecular weight distribution and a uniform comonomer distribution. In extrusion coating, the interest in these polymers is mainly related to the enhanced physical performance of the resulting film. However, from the processing point of view, the metallocene-catalysed polyethylenes can present problems. In this study, a number of metallocene-catalysed linear low-density polyethylenes (m-LLDPE) were characterised with regard to their viscous and elastic properties. Conventional grades of LDPE and LLDPE were included as references. The same grades were used in pilot scale extrusion coating experiments. The processability of the polymers was primarily expressed in terms of neck-in (NI), which describes the lateral reduction of the film width as the film is drawn down into the coating nip, and the draw-down ability (DD), which provides a measure of the ability of a thin film to be drawn into the nip at a high machine speed. A lower NI-value, which is desirable, was noted when the polymer melt exhibited a higher elasticity, expressed in terms of the steady state compliance, the extrudate swell and Trouton's ratio. Factors that had a positive effect on the NI-value tended in general to reduce the draw-down ability. A relation between NI and DD was established, which in principle makes it possible to optimise both NI and DD, based on finding the optimal values of the shear and the elongational viscosities. The results obtained indicate that a low shear viscosity and a high Trouton's ratio provide optimal processability with regard to NI and DD. It was noted that m-LLDPE-grades could be chosen to match the processability of more conventional polymers (expressed in terms of NI and DD). Rheology can be an important tool for such a selection. Note de contenu : - Introduction : Extrusion coating process - Aim of the present study
- Experimental : Materials - Methods - Capillary viscometer measurements - Dynamic-mechanical analysis - Thermal analysis - Extrusion coating
- Results and comments : Thermal analysis - Shear viscosity of the polymer melts - Extensional viscosity of the polymer melts - Extrudate swell behaviour - Dynamic-mechanical properties of the melts - Extrusion coating resultsDOI : 10.3139/217.1690 En ligne : https://drive.google.com/file/d/11BHcCOoi3xQmnVmkjIA3GTZJ9X_dhFYT/view?usp=drive [...] Format de la ressource électronique : Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=16000
in INTERNATIONAL POLYMER PROCESSING > Vol. XVII, N° 3 (09/2002) . - p. 244-253[article]Réservation
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