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Co-extrusion layer multiplication of rheologically mismatched polymers : a novel processing route / R. Huang in INTERNATIONAL POLYMER PROCESSING, Vol. XXX, N° 3 (07/2015)
[article]
Titre : Co-extrusion layer multiplication of rheologically mismatched polymers : a novel processing route Type de document : texte imprimé Auteurs : R. Huang, Auteur ; J. Silva, Auteur ; B. A. Huntington, Auteur ; J. Patz, Auteur ; R. Andrade, Auteur ; P. J. Harris, Auteur ; K. Yin, Auteur ; M. Cox, Auteur ; Roger T. Bonnecaze, Auteur ; Joao M. Maia, Auteur Année de publication : 2015 Article en page(s) : p. 317-330 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Eléments finis, Méthode des
Matières plastiques -- Extrusion:Polymères -- Extrusion
Polyméthacrylate de méthyleLe poly(méthacrylate de méthyle) (souvent abrégé en PMMA, de l'anglais Poly(methyl methacrylate)) est un polymère thermoplastique transparent obtenu par polyaddition dont le monomère est le méthacrylate de méthyle (MMA). Ce polymère est plus connu sous son premier nom commercial de Plexiglas (nom déposé), même si le leader global du PMMA est Altuglas International9 du groupe Arkema, sous le nom commercial Altuglas. Il est également vendu sous les noms commerciaux Lucite, Crystalite, Perspex ou Nudec.
Polystyrène
Polyuréthanes
Rhéologie
Simulation, Méthode de
Stratifiés
Structures multicouches
ThermoplastiquesUne matière thermoplastique désigne une matière qui se ramollit (parfois on observe une fusion franche) d'une façon répétée lorsqu'elle est chauffée au-dessus d'une certaine température, mais qui, au-dessous, redevient dure. Une telle matière conservera donc toujours de manière réversible sa thermoplasticité initiale. Cette qualité rend le matériau thermoplastique potentiellement recyclable (après broyage). Cela implique que la matière ramollie ne soit pas thermiquement dégradée et que les contraintes mécaniques de cisaillement introduites par un procédé de mise en forme ne modifient pas la structure moléculaire.Index. décimale : 668.4 Plastiques, vinyles Résumé : Co-extruded films with up to 65 layers of two rheologically mismatched polymer systems – polystyrene/poly(methylmethacrylate) (PS/PMMA) and hard/soft thermoplastic polyurethanes (TPUs) – were successfully produced using a combination of a 9-layer feedblock, low-pressure drop multiplier dies, and external lubricants. Formation of viscoelastic instabilities was studied using a custom visualization and by finite element method (FEM) simulations of a standard multiplier. The results showed that the flow inside the standard multiplier die is highly non-uniform, with severe gradients in shear and normal stresses and viscous encapsulation occurring mainly in the initial multiplication stages where there is enough material available in the low-viscosity layers to proceed with the encapsulation. To mitigate layer degradation the standard 2- or 3-layer feedblock was replaced with a 9-layer one, thereby decreasing the thickness of each layer at the end of the feedblock. Also, subsequent layering was performed using a low flow resistance die. This new multiplier die yields a more uniform flow profile and imparts a more homogeneous thermo-mechanical history on the melt which results in an improved layer stability. Simulations showed that in the standard die the second normal-stress difference (N2) responsible for elastic instabilities at the edges of the die are very high. These can be reduced by inducing slip at the wall resulting in be much improved layer uniformity and stability. This was accomplished experimentally via the use of external lubricants, and the resulting layered structure was indeed much better than was possible to achieve with the conventional multiplier dies. Note de contenu : - EXPERIMENTAL METHOD : Materials - Rheological measurements - Rheological results - Simulation method - Co-extrusion system and conditions - 9-layer feedblock and the second generation multiplier die
- RESULTS AND DISCUSSION : Visualization of layered structure - The standard die - Engineering solution : 9-layer feedblock and the second generation multiplier die - Reduction of N2 : The effect of external lubricantDOI : 10.3139/217.2955 En ligne : https://drive.google.com/file/d/16YwA6JWwep2d5SI2y2bXF97rG4nBEm5y/view?usp=drive [...] Format de la ressource électronique : Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=24326
in INTERNATIONAL POLYMER PROCESSING > Vol. XXX, N° 3 (07/2015) . - p. 317-330[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 17309 - Périodique Bibliothèque principale Documentaires Disponible Enhanced dispersive mixing in twin-screw extrusion via extension-dominated static mixing elements of varying contraction ratios / H. Chen in INTERNATIONAL POLYMER PROCESSING, Vol. XXXV, N° 1 (03/2020)
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Titre : Enhanced dispersive mixing in twin-screw extrusion via extension-dominated static mixing elements of varying contraction ratios Type de document : texte imprimé Auteurs : H. Chen, Auteur ; V. Pandey, Auteur ; S. Carson, Auteur ; Joao M. Maia, Auteur Année de publication : 2020 Article en page(s) : p. 37-49 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Alliages polymères
Caractérisation
Energie mécanique
Extrudeuse bi-vis
Matières plastiques -- Extrusion
Morphologie (matériaux)
Polypropylène
Polystyrène
RhéologieIndex. décimale : 668.4 Plastiques, vinyles Résumé : Twin screw extruders (TSE) are widely used in polymer blending and compounding operations, since the relatively high stresses they impart on melts and controllable residence times make them highly suitable for mixing operations. However, the mixing action in the industry-standard kneading blocks (KB) is shear-dominated and shear flows are inefficient for dispersive mixing compared with extensional flows. A novel static extensional mixing element (EME) was developed recently by our group with the objective of providing extension-dominated flow during blending and compounding. Dispersive mixing in the EME is provided by flow through stationary hyperbolic converging-diverging (C-D) channels placed along the screw. The improvements in dispersive mixing for immiscible blends using EMEs with wide hyperbolically channels, i.e., low contraction ratios, has been proved. In this work, we begin by performing computational investigations of more extreme contraction geometries to determine the design flexibility limits for the EME. The contractions again showed more extension-dominated flow patterns than the original EME, the drawback being the obvious increase in the pressure drop. However, at extremely high contraction ratios, the entry angle is so shallow that recirculation zones appear at the entrance, which are undesirable, implying that there are geometrical limits above which the EME ceases to be an effective dispersive mixer. Next, experimental validation on the EMEs with different degrees of aggressiveness of the C-D channel were performed and dramatic improvement in droplet breakup (dispersive mixing) in case of immiscible blends is clearly observed at all viscosity ratios and with increasing degree of EME aggressiveness. Note de contenu : - Design and computational validation
- Experiments : Processing equipment
- Rheological characterization
- Morphological analysis
- Results and discussion : Determining the effective viscosity ratio - Blend morphology - Pressure profiles - Specific mechanical energyDOI : https://doi.org/10.3139/217.3857 En ligne : https://drive.google.com/file/d/1-Hew6oS39-220Q_DMmkyDSmhjUgpt9-u/view?usp=drive [...] Format de la ressource électronique : Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=33777
in INTERNATIONAL POLYMER PROCESSING > Vol. XXXV, N° 1 (03/2020) . - p. 37-49[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 21578 - Périodique Bibliothèque principale Documentaires Disponible Fiber length distribution in twin-screw extrusion of fiber-reinforced polymer composites : A comparison between shear extensional mixing / M. Guo in INTERNATIONAL POLYMER PROCESSING, Vol. 36, N° 4 (2021)
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Titre : Fiber length distribution in twin-screw extrusion of fiber-reinforced polymer composites : A comparison between shear extensional mixing Type de document : texte imprimé Auteurs : M. Guo, Auteur ; X. Li, Auteur ; Joao M. Maia, Auteur Année de publication : 2021 Article en page(s) : p. 350-357 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Caractérisation
Composites à fibres -- Extrusion
Composites à fibres de carbone
Composites à fibres de verre
Composites à fibres longues
Composites à fibres polymères
Compoundage
Extrudeuse bi-vis
Polyéthylène glycol
Polyéthylène téréphtalate
Polypropylène
Résistance à la tractionIndex. décimale : 668.4 Plastiques, vinyles Résumé : New extensional mixing elements (EME) for twin-screw extrusion were applied to compound glass fibers (GF), carbon fibers (CF) or polyethylene terephthalate fibers (PETF) reinforced polymer composites with polymer matrix of polypropylene (PP) or polyethylene oxide (PEO) and the resulting fiber degradation upon processing was evaluated and compared with compounding via shear flow-dominated kneading blocks (KB). Composites structures were characterized in terms of fiber length and distribution, and cumulative length ratio, at five locations along the mixing zone. Although significant fiber breakage was achieved for both configurations, it was markedly lower in composites processed using the EME, because whereas the high shear stress kneading motion in the KB degrades fibers significantly, fiber breakup is significantly minimized by the alignment induced by the EME prior to flow in the high-stress regions. Note de contenu : - Materials
- Compounding
- Characterization
- Table 1 : Aspect ratio (AR), tensile strength (TS), and initial length (L0) of the fibers; number average fiber length (Ln) and weight average fiber length (Lw) of the five composites processed through the KB and the EME screw configurations (at position E)
- Table 2 : Number average fiber length (Ln) and weight average fiber length (Lw) of PP/GF and PP/CF composites at different locations of the mixing zone of the KB and the EME screw configurations
- Table 3 : Number average fiber length (Ln) and weight average fiber length (Lw) of HPEO/PETF and LPEO/PETF composites at different locations of the mixing zone of the KB and the EME screw configurationsDOI : https://doi.org/10.1515/ipp-2020-3978 En ligne : https://drive.google.com/file/d/1ED81O8focju1aRW51xcjizVHorqwRS7w/view?usp=shari [...] Format de la ressource électronique : Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=36707
in INTERNATIONAL POLYMER PROCESSING > Vol. 36, N° 4 (2021) . - p. 350-357[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 23734 - Périodique Bibliothèque principale Documentaires Disponible