Evaluation of a model describing the advancing flow front in injection moulding / F. Pisciotti in INTERNATIONAL POLYMER PROCESSING, Vol. XVII, N° 2 (06/2002)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XVII, N° 2 (06/2002) . - p. 133-145 Titre : Evaluation of a model describing the advancing flow front in injection moulding Type de document : texte imprimé Auteurs : F. Pisciotti, Auteur ; A. Boldizar, Auteur ; M. Rigdahl, Auteur ; G. Aronsson, Auteur ; M. Rigdahl Année de publication : 2002 Article en page(s) : p. 133-145 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 668.9 Polymères Résumé : The simulation of the advancing flow front during mould filling in the injection moulding cycle is important as a way of anticipating manufacturing defects, particularly different types of welds, air traps, cold spots and hot spots. The purpose of the present work was to evaluate a model (the distance model) simulating the advancing flow front and predicting potential issues related to the progression of the flow front such as welds and air traps. The distance model is based on a mathematical theory of Hele-Shaw flow for strongly shear-thinning fluids, i. e. fluids with a power-law index, n, equal to 0,3 or preferably less. Two grades of general-purpose polystyrene were selected according to their abilities to shear thin (weakly or moderately strong) at the selected processing temperature and in the typical shear rate range of the injection moulding process. The two grades were injection moulded into twelve mould configurations derived from two similar single-gated moulds. The flow length from the gate to the weld was measured in the mouldings obtained at three distinct rates of filling (conventional, slower and faster) and compared to the flow lengths obtained by the distance model. Good agreement was found between the predicted flow lengths and the experimental flow lengths at the conventional and faster filling conditions. Larger deviations between simulation and experiment were found at the slower filling rate, particularly for the weakly shear-thinning polystyrene grade. Some comparisons were also made with the predictions obtained using the commercial simulation code Moldflow. A comparison between the advancing front predictions of the distance model and experimental short shots of a commercial polypropylene grade in a lure-box type of mould geometry showed that the distance model, despite its simplicity, could probably be used to detect welds and air traps in more complex and practice-related mouldings. Note de contenu : - INTRODUCTION : Manufacturing defects related to mould filling - The distance model - - EXPERIMENTAL : Materials - Mould geometry - Processing - Flow length measurement - RESULTS AND DISCUSSION : Weld detection - The advancing flow front - A practice-related moulding DOI : 10.3139/217.1682 En ligne : https://drive.google.com/file/d/15mW8TQTMJGeBpUZ0EWylo9zGHAYQhFm4/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=15942 [article]

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Injection moulding and mechanical properties of recovered polypropylene / F. Pisciotti in INTERNATIONAL POLYMER PROCESSING, Vol. XX, N° 3 (09/2005)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XX, N° 3 (09/2005) . - p. 257-264 Titre : Injection moulding and mechanical properties of recovered polypropylene Type de document : texte imprimé Auteurs : F. Pisciotti, Auteur ; M. Rigdahl, Auteur ; A. Boldizar, Auteur Année de publication : 2005 Article en page(s) : p. 257-264 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 668.9 Polymères Résumé : This work is a part of a study aiming at assessing the processability of recovered polypropylene in relation to the mechanical and aesthetic performance of as-manufactured and heat aged mouldings. The effects of processing and heat ageing on the mechanical properties of injection-moulded recovered polypropylene were studied here. A similar grade of virgin polypropylene was used as a reference. Multipurpose test specimens were manufactured with a two-cavity mould, according to decoupled moulding procedures. The mouldings were aged at 100 °C for 170 h and 340 h. The stiffness, the strength, the elongation at break and the Charpy impact resistance of asmoulded and heat-treated materials were investigated. The results show that the recovered polypropylene could be processed as the analogous virgin grade. Insignificant changes in the measured properties due to the different filling conditions were observed for each polypropylene used. The stiffness and strength of the recycled polypropylene was systematically 20% lower than that of the analogous virgin grade, whereas the impact resistance of the recycled grade was on average 40% higher than that for the virgin grade. There was no significant difference in the elongation at break of the two materials. After the short ageing period, an increase in stiffness and strength of the materials was observed, together with a sharp decrease in the elongation at break and a modest increase in the impact resistance. This was related to re-crystallisation. The long ageing period reduced the stiffness and strength of the materials but there was no significant change in the elongation at break or in the impact resistance. DOI : 10.3139/217.1887 En ligne : https://drive.google.com/file/d/1TV-Z9jY5eCd9DYlxTh6I8Z2746KA0zeu/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=3062 [article]

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The gloss of injection-moulded recovered polypropylene / F. Pisciotti in INTERNATIONAL POLYMER PROCESSING, Vol. XX, N° 3 (09/2005)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XX, N° 3 (09/2005) . - p. 250-256 Titre : The gloss of injection-moulded recovered polypropylene Type de document : texte imprimé Auteurs : F. Pisciotti, Auteur ; M. Rigdahl, Auteur ; A. Boldizar, Auteur Année de publication : 2005 Article en page(s) : p. 250-256 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 668.9 Polymères Résumé : In our recent work, it was shown that the rate of filling during injection moulding did not significantly affect the tensile and impact properties of recovered and virgin polypropylene, whereas significant changes in the properties were observed after ageing at 100 °C. The purpose of the present work was to extend the former study to include the effects of processing and ageing on surface-appearance-related properties, in particular the gloss. In-mould rheology and gate-seal analyses were performed in order to select the filling and post-filling processing windows, respectively. The influences of filling rate, holding and cooling times on the gloss measured in the gate area and at the far end of the moulded specimens were evaluated. The mould used had an embossed surface giving test plaques with a matte appearance. The results showed that the gloss variedby about 30 to 40% within the filling window obtained by in-mould rheology. The slight gloss difference between the two PP-grades noted at the lowest injection speed vanished with increasing filling rate. Gloss differences were observed between the gate area and the far end of each processed moulding, again at the lowest injection speed. The materials processed at a high filling rate exhibited a fairly constant gloss as the holding time increased regardless of the position of the analysed region, whereas a more significant decrease was noted in the case of the mouldings processed at the low filling rate. The cooling time had a negligible effect on the gloss in comparison to the effect of filling rate. Ageing at 100 °C for 240 h increased the gloss level, especially at the far end of the moulding, but only for specimens manufactured at the lowest filling rate. Roughness measurements with a profilometer showed that the gloss development during processing and ageing was related to the topographical matching between the developing polymer surface and the mould topography. DOI : 10.3139/217.1886 En ligne : https://drive.google.com/file/d/1IWISaY9A1Z5DCjS6sA5WEbcfA4RULDN0/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=3061 [article]

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