Controllable self-organization of polyphenylene oxide honeycomb microstructure / H. Chen in INTERNATIONAL POLYMER PROCESSING, Vol. XXVII, N° 4 (08/2012)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XXVII, N° 4 (08/2012) . - p. 486-492 Titre : Controllable self-organization of polyphenylene oxide honeycomb microstructure Type de document : texte imprimé Auteurs : H. Chen, Auteur ; X. Shang, Auteur ; D. Zhang, Auteur ; I. Hagiwara, Auteur Année de publication : 2012 Article en page(s) : p. 486-492 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Films plastiques Hydrophobie Microstructures Oxyde de polyphénylène Plastiques alvéolaires Structure en nid d'abeilles Systèmes auto-organisés Index. décimale : 668.9 Polymères Résumé : Polymer films with patterned microstructure have been widely applied in various industrial areas such as micro reactors, chemical sensors and micro-molded template etc. In this paper, a self-supporting polymer film with regular honeycomb microstructure is fabricated by self-organization via evaporation of polyphenylene oxide (PPO) solution in which carbon disulfide is used as solvent under humid ambience. Apart from investigation of self-organization mechanism of PPO honeycomb including nucleation, growth of water droplets condensed upon liquid supporting substrate, the quantitative relationship between honeycomb microstructure and ambient conditions is built through tremendous self-organization experiments. The controllable formation of honeycomb microstructure with desirable hydrophobicity was achieved by use of built quantitative relationship. Moreover, hydrophobicity mathematical model of self-organized honeycomb thin film was proposed, and its validation was experimentally verified. Note de contenu : - PPO SELF-ASSEMBLY EXPERIMENT - RESULTS AND DISCUSSION : Stability of the self-organized film - Influence of ambient humidity on self-organized film - Influence of solution concentration on the self-organized film - Controllability of honeycomb microstructure formation DOI : 10.3139/217.2606 En ligne : https://drive.google.com/file/d/1pHrueSKIlee_MtkTq9VWdrzJ_1bpmlmE/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=15772 [article]

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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)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XXXV, N° 1 (03/2020) . - p. 37-49 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 Rhéologie Index. 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 energy DOI : 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 : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=33777 [article]

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On-line visualization of PS/PP melting mechanisms in a co-rotating twin screw extruder / H. Chen in INTERNATIONAL POLYMER PROCESSING, Vol. XIX, N° 4 (12/2004)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XIX, N° 4 (12/2004) . - p. 342-349 Titre : On-line visualization of PS/PP melting mechanisms in a co-rotating twin screw extruder Type de document : texte imprimé Auteurs : H. Chen, Auteur ; Uttandaraman Sundararaj, Auteur ; K. Nandakumar, Auteur ; Marc D. Wetzel, Auteur Année de publication : 2004 Article en page(s) : p. 342-349 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 668.9 Polymères Résumé : The melting and deformation mechanisms of polystyrene (PS) and polypropylene (PP) blends were investigated through online visualization of the co-rotating twin-screw extrusion process. Two compositions, PP/PS (80 : 20) and PS/PP (80: 20) were chosen as the model systems for this study. A sliding barrel technique was used to realize the on-line visualization using a glass window in the barrel. The axial temperature and pressure profiles along the screw channel were measured using the same sliding technique. It was found that in the PP/PS (80 : 20) blend, in which PP was the major phase, there was a combined melting of PS and PP, whereas in the PS/PP (80 : 20) blend, in which PS was the major phase, there was initial melting of PS alone and then combined melting of PS and PP. In the partially filled region, heat conduction from the hot barrel was the major source for heating polymer pellets under the conditions studied here; while in the fully filled region, viscous energy dissipation (VED) generated most of the heat for melting of polymer pellets. The pressure profiles along the extrusion channel gave us insight into the melting process for the two blends. It was found that if there was some molten polymer in the fully filled region, the overall melting process was accelerated due to heating from viscous dissipation. DOI : 10.3139/217.1839 En ligne : https://drive.google.com/file/d/10PY5_vzTyQSVXV4mDMnjen2b4gCW2d3l/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=3266 [article]

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