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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In-process rheometry studies of LDPE compounds / A. L. Kelly in INTERNATIONAL POLYMER PROCESSING, Vol. XV, N° 4 (12/2000)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XV, N° 4 (12/2000) . - p. 355-360 Titre : In-process rheometry studies of LDPE compounds : Part I : Unfilled resin Type de document : texte imprimé Auteurs : A. L. Kelly, Auteur ; M. Woodhead, Auteur ; D. Barnwell, Auteur ; K. Martin, Auteur ; P. D. Coates, Auteur Année de publication : 2000 Article en page(s) : p. 355-360 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 668.9 Polymères Résumé : The initial part of a comprehensive study into the investigation and validation of in-process measurements on a low density polyethylene (LDPE) compound during extrusion is reported. An unfilled, commercial grade of low density polyethylene was processed using fully instrumented, computer monitored, single and twin screw extruders in the Interdisciplinary Research Centre (IRC) laboratories, University of Bradford. Three in-process rheometers were used; a prototype Rosand capillary on-line rheometer (OLR), a four sensor slit die in-line rheometer (ILR) and a six sensor slit die ILR. Off-line comparisons were carried out using a Rosand RH7 twin bore capillary rheometer. All devices allowed shear flow characterisation at a range of processing rates, and the capillary rheometers also provided a measurement of entry pressure drop through the use of orifice dies. The six-sensor ILR also allowed measurement of entry pressure drop into the slit, although the differences in flow geometry meant these measurements were not directly comparable with the capillary devices, and exit pressures were extrapolated from ILR pressure drops. The in-process devices exhibited very good agreement with measurements made off-line, in both shear flow and entry pressures. In-line slit die measurements were very close to those made using capillary dies, despite the in-line tests being non-isothermal and employing a different geometry of measurement section. Differences in melt rheology between single and twin extrusion were observed, due to the amount of mechanical work input by each extruder. Overall, good agreement was observed from the four different routes to measurement, for the LDPE examined. DOI : 10.3139/217.1612 En ligne : https://drive.google.com/file/d/1_iQvHCt9XuClrlRnNyA6lbtfAdKCTCbF/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=16146 [article]

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In-process rheometry studies of LDPE compounds / A. L. Kelly in INTERNATIONAL POLYMER PROCESSING, Vol. XV, N° 4 (12/2000)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XV, N° 4 (12/2000) . - p. 361-368 Titre : In-process rheometry studies of LDPE compounds : Part II : Magnesium hydroxide filled Type de document : texte imprimé Auteurs : A. L. Kelly, Auteur ; M. Woodhead, Auteur ; P. D. Coates, Auteur ; D. Barnwell, Auteur ; K. Martin, Auteur Année de publication : 2000 Article en page(s) : p. 361-368 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 668.9 Polymères Résumé : Screw extrusion/Mixing - The second part of a comprehensive study into the investigation and validation of in-process measurements on a low density polyethylene compound during extrusion is reported. A commercial grade of branched low density polyethylene was used in the study, compounded with various levels of magnesium hydroxide flame retardant filler, up to 50% by weight. In-line and on-line rheometry were used to monitor melt flow behaviour during single screw and twin screw extrusion; off-line capillary rheometry was performed on the compound before and after extrusion, to examine any change in rheology. Morphological observations were made using scanning electron microscopy, and molecular characterisations carried out using gel permeation chromatography. In-process rheometry was found to be able to detect the presence of filler at low and high loadings, but was unable to discriminate between intermediate levels. Off-line rheometry indicated that twin screw extrusion altered the rheology of the compound, and capillary wall slip was found to increase after extrusion. Morphological observation indicated that filler in the compound was better dispersed after extrusion, especially at high volume fractions. Molecular weight and polydispersity of the LDPE were shown to increase after extrusion, more so in the case of low filler loadings. Overall, in-process measurements provided useful rheological data, and the compound was found to exhibit complex, process-dependent rheology. DOI : 10.3139/217.1613 En ligne : https://drive.google.com/file/d/1Mw1gsaUXcM_GqpMC90x-25j8e0Zrht8o/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=16154 [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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Real-time diagnosis of micro powder injection molding using integrated ultrasonic sensors / C.-C. Cheng in INTERNATIONAL POLYMER PROCESSING, Vol. XXII, N° 2 (05/2007)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XXII, N° 2 (05/2007) . - p. 140-145 Titre : Real-time diagnosis of micro powder injection molding using integrated ultrasonic sensors Type de document : texte imprimé Auteurs : C.-C. Cheng, Auteur ; Y. Ono, Auteur ; B. D. Whiteside, Auteur ; E. C. Brown, Auteur ; C.-K. Jen, Auteur ; P. D. Coates, Auteur Année de publication : 2007 Article en page(s) : p. 140-145 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 668.9 Polymères Résumé : Real-time Diagnosis of Micro Powder Injection Molding Using Integrated Ultrasonic Sensors Real-time diagnostics of ceramic powder injection molding using a commercial micromolding machine was performed using ultrasound. Miniature ultrasonic sensors were integrated onto the mold insert. Melt front, solidification, temperature variation and part detachment of the feedstock inside the mold cavity were observed. It has been demonstrated that ultrasonic velocity in feedstock inside the mold cavity, the ultrasonic contact duration during which the part and mold are in contact, and holding pressure can be used to assist with optimization of injection and cooling parameters to minimize energy consumption and maximize process efficiency. DOI : 10.3139/217.0013 En ligne : https://drive.google.com/file/d/1xrDfT5JbzqF3iyV4NMV3lWcMsfiAlg2T/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=2752 [article]

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