Effect of processing history on the sintering of ethylene copolymers / S. A Guillén-Castellanos in INTERNATIONAL POLYMER PROCESSING, Vol. XVIII, N° 1 (03/2003)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XVIII, N° 1 (03/2003) . - p. 87-90 Titre : Effect of processing history on the sintering of ethylene copolymers Type de document : texte imprimé Auteurs : S. A Guillén-Castellanos, Auteur ; W. Lin, Auteur ; C. T. Bellehumeur, Auteur ; M. Weber, Auteur Année de publication : 2003 Article en page(s) : p. 87-90 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 668.9 Polymères Résumé : Polymer sintering plays a major role in processes such as rotational molding, governing the heating cycle and the properties of the final parts. There is evidence to suggest that the material molecular structure, molecular order and morphology are of importance in the sintering process. To date, however, there has been no satisfactory explanation as for their role in polymer sintering. One objective of this work is to examine the sintering behavior of ethylene copolymers under conditions related to the rotational molding process and to determine the relative effects of the polymer molecular structure and morphology on the sintering process. Sintering experiments were conducted under isothermal and non-isothermal conditions using both powder and cylindrical particles. It was found that the trends observed for the sintering of powder were consistent with the predictions of Newtonian sintering models. Sintering results obtained using cylindrical particles, however, showed significant differences not seen when using powder particles. These were attributed to the differences in the surface area between the two types of particles. It is speculated that the effect of material properties other than viscosity and elasticity are enhanced when cylindrical particles are used. DOI : 10.3139/217.1720 En ligne : https://drive.google.com/file/d/1__ayoDi7JbqkQScnu5PMSw-frEQg9_tK/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=15854 [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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