Effects of cooling ways on the structure of polypropylene hollow fiber membranes prepared by stretching / D.-J. Luo in INTERNATIONAL POLYMER PROCESSING, Vol. XXXIV, N° 2 (05/2019)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XXXIV, N° 2 (05/2019) . - p. 172-181 Titre : Effects of cooling ways on the structure of polypropylene hollow fiber membranes prepared by stretching Type de document : texte imprimé Auteurs : D.-J. Luo, Auteur ; F.-J. Wei, Auteur ; H.-J. Shao, Auteur ; K.-Z. Zhang, Auteur ; Z.-Y. Cui, Auteur ; J. Yu, Auteur ; S.-H. Qin, Auteur Année de publication : 2019 Article en page(s) : p. 172-181 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Essais dynamiques Extrusion filage Fibres creuses Membranes (technologie) Morphologie (matériaux) Polypropylène Porosité Surfaces (Physique) Systèmes de refroidissement Traction (mécanique) Index. décimale : 668.4 Plastiques, vinyles Résumé : Air, water, and DINCH (Di-isononyl-cyclohexane-1,2-dicarboxylate) were selected as the cooling media to prepare polypropylene hollow fiber membranes by melt spinning. The effects of various cooling ways with different cooling rates on the row-nucleated lamellar crystallization were investigated. The crystallinity, orientation and arrangement of the crystals were examined by differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), and small-angle X-ray scattering (SAXS). Membrane morphology was observed by SEM. The less uniform pores, a layer of amorphous phase, and only a small part of slit-shaped pores were observed on the surface of samples when water and DINCH were used as the heat transfer medium because the fast cooling rate froze the surface molecules and decreased the crystallinity and orientation. However, when air was used as the cooling medium, the higher crystallinity and the better orientation of the annealed hollow fibers were obtained mainly due to the slow cooling rate. Corresponding hollow fiber membranes prepared by stretching had better interconnectivity of pores and larger pure water flux. Thus this study explains why air was selected as the cooling medium to prepare polypropylene hollow fiber membranes which can have larger pure water flux. Also, it provides new insights into the structure control of polypropylene hollow fiber membranes by stretching in order to prepare membranes with high strength. Note de contenu : - EXPERIMENTAL : Materials - Membrane preparation - Differential Scanning Calorimetry - Surface morphology - Tensile properties - Elastic recovery rate - RESULTS AND DISCUSSION : Crystallization and DSC analysis - SAXS and WAXD analysis - Tensile properties and elastic recovery rate - Surfaces morphologies - Porosity and pure water flux DOI : 10.3139/217.3638 En ligne : https://drive.google.com/file/d/1T1rC3UNtaRnspchVpMtyqp5EaKrJkRWH/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=32393 [article]

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Morphology and isothermal crystallization kinetics of polypropylene/poly(ethylene-co-vinyl alcohol) blends / D.-J. Luo in INTERNATIONAL POLYMER PROCESSING, Vol. XXXIV, N° 2 (05/2019)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XXXIV, N° 2 (05/2019) . - p. 195-208 Titre : Morphology and isothermal crystallization kinetics of polypropylene/poly(ethylene-co-vinyl alcohol) blends Type de document : texte imprimé Auteurs : D.-J. Luo, Auteur ; H.-J. Shao, Auteur ; F.-J. Wei, Auteur ; K.-Z. Zhang, Auteur ; Z.-Y. Cui, Auteur ; J. Yu, Auteur ; S.-H. Qin, Auteur Année de publication : 2019 Article en page(s) : p. 195-208 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Alliages polymères Caoutchouc Copolymère éthylène alcool de vinyle C'est aujourd'hui le matériau le plus utilisé dans l'emballage rigide alimentaire. Il peut être utilisé avec des matériaux de structure comme le polyéthylène, polypropylène ou polystyrène. Ce copolymère présente une excellente imperméabilité à l'oxygène, au gaz carbonique et aux arômes, à condition de protéger de l'influence de l'humidité qui fait chuter fortement ses performances. Pour palier cet inconvénient, il est souvent pris en sandwich dans des structures multicouches à base de polyoléfines PE ou PP peu sensibles à l'humidité. Il est utilisé pour les emballages de compotes, jus de fruits, fromages, sauces, crèmes et yaourts, mayonnaise, sauce tomate... Cristallisation Diffractométrie de rayons X Polypropylène Index. décimale : 668.4 Plastiques, vinyles Résumé : Polypropylene (PP)/poly(ethylene-co-vinyl alcohol) (EVOH) blends were prepared by melt blending using PP-g-MAH as a compatabilizer. The microstructure and rheological behavior of PP/EVOH blends were studied. The results showed the that EVOH particles were uniformly dispersed in the PP matrix and inhibited the mobility of PP chains. The isothermal crystallization kinetics and morphology development of PP/EVOH blends were compared with that of pure PP. It was found that the EVOH essentially acted as an effective nucleating agent for PP, which could significantly increase the nucleation rate because the EVOH molecules in PP/EVOH blends aggregated together to form interface. Therefore, the introduction of EVOH increased the overall rate of isothermal crystallization compared with pure PP, although the PP molecular chains would be hindered seriously if excessive amounts of EVOH were added. X-ray diffraction showed that pure PP and PP/EVOH blends exhibited an identical crystal structure, and the crystallinity of the PP phase in the blends was not significantly different from that of pure PP. Note de contenu : - EXPERIMENTAL : Materials - Sample preparation - Characterization - RESULTS AND DISCUSSION : Microstructural and viscoelastic properties of PP/EVOH blends - Non-isothermal crystallization behavior of PP/EVOH blends - Isothermal crystallization kinetics of PP/EVOH blends - Melting behavior of isothermally crystallized PP/EVOH blends - Morphology and microstructure of PP/EVOH blends DOI : 10.3139/217.3589 En ligne : https://www.degruyter.com/document/doi/10.3139/217.3589/pdf Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=32395 [article]

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