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Determination of thermal response on mold surface and recommendation of feasible heating time and gas flow rate for a circular cavity by gas preheating / S.-W. Chang in INTERNATIONAL POLYMER PROCESSING, Vol. XXVII, N° 1 (03/2012)
[article]
Titre : Determination of thermal response on mold surface and recommendation of feasible heating time and gas flow rate for a circular cavity by gas preheating Type de document : texte imprimé Auteurs : S.-W. Chang, Auteur ; Y. H. Lee, Auteur Année de publication : 2012 Article en page(s) : p. 30-39 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Moules d'injection Tags : 'Surface moule' 'Temps chauffage' 'Préchauffage haute température gaz' 'Réponse thermique' 'Modèle mathématique' 'Transfert masse' bi-fluide' 'Analyse dimensionnelle' Index. décimale : 668.9 Polymères Résumé : This paper studies the thermal response on the mold surface of a circular cavity in the preheating process by high-temperature gas via a numerical approach, where the heat and mass transfer inside the cavity and mold are predicted by a two-fluid model. The dimensionless parameter group is identified from a dimensional analysis of the gas preheating problem. The correlations among dimensionless parameters are established by a least square method applied to the numerical predictions. The upper limit of the temperature rise on the cavity surface at a given gas flow rate is found approximately proportional to the square root of Q* and h*, respectively. The lower limit of gas flow rate to achieve a given temperature rise on the cavity surface is inversely proportional to h* but grows with (Q*)1.5. The first limiting line to describe the dependence of Q* on t* is independent of h* and T*, but the second one is governed by Q*c. For reaching a specified temperature rise on the cavity surface, the growth in the thickness of thermal resistive layer reduces the required preheating time but increases the corresponding gas flow rate. The dependence of (t∗ƒ, Q∗ƒ) on the parameter group (T*, h*) is given in this study to obtain the reasonable combinations of (t*ƒ , Q*ƒ) based on the balance between the allowable preheating time and heating capacity. Note de contenu : - MATHEMATICAL MODEL : Governing equations - Boundary conditions - Numerical scheme
- DESCRIPTION OF STUDIED CASEDOI : 10.3139/217.2500 En ligne : https://drive.google.com/file/d/1Ek2BafMIA1ak7SI7Jm5gXPBhWvYVbtNc/view?usp=drive [...] Format de la ressource électronique : Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=13719
in INTERNATIONAL POLYMER PROCESSING > Vol. XXVII, N° 1 (03/2012) . - p. 30-39[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 13722 - Périodique Bibliothèque principale Documentaires Disponible Effects of sparse long chain branching on the spinning stability of LLDPEs / M. J. Bortner in INTERNATIONAL POLYMER PROCESSING, Vol. XIX, N° 3 (09/2004)
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Titre : Effects of sparse long chain branching on the spinning stability of LLDPEs Type de document : texte imprimé Auteurs : M. J. Bortner, Auteur ; P. J. Doerpinghaus, Auteur ; D. G. Baird, Auteur Année de publication : 2004 Article en page(s) : p. 236-243 Note générale : Bibliogr. Langues : Anglais (eng) Tags : Polymérisation 'Modèle mathématique' 'Réaction cinétique' 'Contrôle du process' Index. décimale : 668.9 Polymères Résumé : The influence of sparse long chain branching on the onset and propagation of isothermal draw resonance in fiber spinning of polyethylene melts was investigated. Six polyethylene melts were used in this study: three sparsely branched metallocene polyethylenes, a linear low-density metallocene polyethylene, a conventional linear low-density polyethylene, and a conventional low-density polyethylene (LDPE). The sparsely branched metallocene polyethylenes have almost identical shear rheology and molecular weight distributions, but strain harden to different extents under extensional deformation because of slight differences in the amount of sparse long chain branching. Critical draw ratios and the ratios of minimum to maximum diameter were found to be different for each of these polyethylenes. The two linear low-density polyethylenes, which have no long chain branching, had critical draw ratios similar to those of the sparsely branched polyethylenes, but failed (necked to the point of filament breakage) during monofilament extrusion at draw ratios significantly lower than those measured for the sparsely branched polyethylenes. In contrast, the LDPE, which has the highest degree of branching and largest molecular weight distribution, had a much higher critical draw ratio than that obtained for the other five polyethylenes. These results suggest that the degree of extensional strain hardening, arising from differences in long chain branching, has a significant effect on the onset and propagation of draw resonance in isothermal fiber spinning. In the case of LLDPE, broadening the MWD seemed to affect the drawability of LLDPE, but had no effect on the critical draw ratio. DOI : 10.3139/217.1824 Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=3105
in INTERNATIONAL POLYMER PROCESSING > Vol. XIX, N° 3 (09/2004) . - p. 236-243[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 001029 - Périodique Bibliothèque principale Documentaires Disponible