In-process monitoring of micromoulding – assessment of process variation / B. R. Whiteside in INTERNATIONAL POLYMER PROCESSING, Vol. XX, N° 2 (06/2005)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XX, N° 2 (06/2005) . - p. 162-169 Titre : In-process monitoring of micromoulding – assessment of process variation Type de document : texte imprimé Auteurs : B. R. Whiteside, Auteur ; P. D. Coates, Auteur ; Mike T. Martyn, Auteur Année de publication : 2005 Article en page(s) : p. 162-169 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 668.9 Polymères Résumé : Advances in micromoulding technology are leading to complex, net-shape products having sub-milligramme masses with micro-scale surface features in a range of polymer and nanocomposite materials. For such small components subjected to the extreme stress, strain-rate and temperature gradients encountered in the micromoulding process, detailed process monitoring is desirable to highlight variations in moulding conditions and assist in creating a viable manufacturing process with acceptable quality products. This paper covers the implementation of a suite of sensors on a commercial micromoulding machine and detailed computer monitoring during processing of a polyacetal component over a range of processing conditions. The results determined that cavity pressure curve integral data provides the most sensitive factor for characterisation of a moulding process of a 0.34mm3 (0.49mg) product. The repeatability of the process is directly compared with that of a 15.6mm3 (22.2mg) product and shown to be inferior. DSC measurements of the whole products indicated little variation in average crystallinity of the products manufactured over a mould temperature range of 30 to 130°C. DOI : 10.3139/217.1876 En ligne : https://drive.google.com/file/d/1GBlj5iRVKeyUDCaJsfWi3Nv8-j-bJaL7/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=3076 [article]

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Pressure variation during interfacial instability in the coextrusion of low density polyethylene melts / Mike T. Martyn in INTERNATIONAL POLYMER PROCESSING, Vol. XXVIII, N° 5 (11/2013)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XXVIII, N° 5 (11/2013) . - p. 516-527 Titre : Pressure variation during interfacial instability in the coextrusion of low density polyethylene melts Type de document : texte imprimé Auteurs : Mike T. Martyn, Auteur ; P. D. Coates, Auteur Année de publication : 2013 Article en page(s) : p. 516-527 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Etat fondu (matériaux) Instabilités (physique) Interfaces solide-liquide Matières plastiques -- Extrusion Polyéthylène basse densité Pression -- Mesure Rhéologie Index. décimale : 668.4 Plastiques, vinyles Résumé : Pressure variation during the coextrusion of two low density polyethylene melts was investigated. Melt streams were delivered to a die from two separate extruders to converge in a 30°° geometry to form a two layer extrudate. Melt flow in the confluent region and die land to the die exit was observed through side windows of a visualisation cell. Stream velocity ratio was varied by control of extruder screw speeds. Layer thickness ratios producing wave type interfacial instability were quantified for each melt coextruded on itself and for the combined melts. Stream pressures and screw speeds were monitored and analysed. Wave type interfacial instability was present during the processing of the melts at specific, repeatable, stream layer ratios. Increased melt elasticity appeared to promote this type of instability. Analysis of process data indicates little correlation between perturbations in extruder screw speeds and stream pressures. The analysis did however show covariance between the individual stream pressure perturbations. Interestingly there was significant correlation even when interfacial instability was not present. We conclude that naturally occurring variation in extruder screw speeds do not perturb stream pressures and, more importantly, natural perturbations in stream pressures do not promote interfacial instability. Note de contenu : - EXPERIMENTAL : Materials - Coextrusion and rheo-optical arrangment - Process measurements - RESULTS AND DISCUSSION : Melt rheology and process typical viscoelastic behavior - Critical layer ratios - Process pressure and screw speed correlations - Process pressure variation DOI : 10.3139/217.2786 En ligne : https://drive.google.com/file/d/1BWx2PICGbxTQRgbU3_v-jIEGRxqGmNm5/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=19898 [article]

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