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Auteur Lih-Sheng Turng |
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Characterization of stereocomplex polylactide/nanoclay nanocomposites / Yortha Srithep in INTERNATIONAL POLYMER PROCESSING, Vol. XXXII, N° 1 (03/2017)
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Titre : Characterization of stereocomplex polylactide/nanoclay nanocomposites Type de document : texte imprimé Auteurs : Yortha Srithep, Auteur ; D. Pholharn, Auteur ; Lih-Sheng Turng, Auteur Année de publication : 2017 Article en page(s) : p. 121-128 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Analyse thermique
Argile
Diffractométrie de rayons X
Nanoparticules
Nucléation
Polylactique, AcideL'acide polylactique (anglais : polylactic acid, abrégé en PLA) est un polymère entièrement biodégradable utilisé dans l'alimentation pour l'emballage des œufs et plus récemment pour remplacer les sacs et cabas en plastiques jusqu'ici distribués dans les commerces. Il est utilisé également en chirurgie où les sutures sont réalisées avec des polymères biodégradables qui sont décomposés par réaction avec l’eau ou sous l’action d’enzymes. Il est également utilisé pour les nouveaux essais de stent biodégradable.
Le PLA peut-être obtenu à partir d'amidon de maïs, ce qui en fait la première alternative naturelle au polyéthylène (le terme de bioplastique est utilisé). En effet, l'acide polylactique est un produit résultant de la fermentation des sucres ou de l'amidon sous l'effet de bactéries synthétisant l'acide lactique. Dans un second temps, l'acide lactique est polymérisé par un nouveau procédé de fermentation, pour devenir de l'acide polylactique.
Ce procédé conduit à des polymères avec des masses molaires relativement basses. Afin de produire un acide polylactique avec des masses molaires plus élevées, l'acide polylactique produit par condensation de l'acide lactique est dépolymérisé, produisant du lactide, qui est à son tour polymérisé par ouverture de cycle.
Le PLA est donc l’un de ces polymères, dans lequel les longues molécules filiformes sont construites par la réaction d’un groupement acide et d’une molécule d’acide lactique sur le groupement hydroxyle d’une autre pour donner une jonction ester. Dans le corps, la réaction se fait en sens inverse et l’acide lactique ainsi libéré est incorporé dans le processus métabolique normal. On obtient un polymère plus résistant en utilisant l'acide glycolique, soit seul, soit combiné à l’acide lactique.
Stabilité thermique
ThermogravimétrieIndex. décimale : 668.4 Plastiques, vinyles Résumé : Poly(L-lactide) (PLLA)/poly(D-lactide) (PDLA)/nanoclay nanocomposites with nanoclay contents ranging from 1% to 8% w/w were prepared by melt blending using an internal mixer. Wide-angle X-ray diffraction (XRD) and differential scanning calorimetry (DSC) results confirmed that complete stereocomplex polylactide (PLA) crystallites without any homocrystallites were produced when equal amounts of PLLA and PLDA were mixed. The nanoclay in the stereocomplex polylactide nanocomposites acted as a nucleating agent that significantly enhanced stereocomplex crystallization, resulting in smaller and finer spherulites. Compared to neat PLLA, the melting temperature of the stereocomplex polylactide and its nanocomposites was about 55°C higher. The crystallization temperature of the stereocomplex nanocomposites was also 16°C and 55°C higher than that of the stereocomplex PLA and neat PLLA, respectively. These significant increases in transition temperatures improved the thermal stability of the stereocomplex nanocomposites compared to regular polylactide, which was confirmed by thermogravimetric analysis (TGA). The TGA results also showed that increasing nanoclay content increased the thermal stability of the stereocomplex nanocomposites. Finally, XRD and transmission electron microscopy showed an intercalation nanoclay basal spacing of 3.22 nm in the stereocomplex nanocomposites; a slight increase from the 1.86 nm basal spacing in the as-received nanoclay. Note de contenu : - EXPERIMENTS : Materials - Blend preparation - Material characterization
- RESULTS AND DISCUSSION : Melt blending of PLLA and PDLA at 200°C - Stereocomplex formation and nanocomposite pattern and morphologies - Thermal properties and calorimetry results - Thermal stability - Polarized optical microscopyDOI : 10.3139/217.3310 En ligne : https://drive.google.com/file/d/1lXVQ16qhAlZdtG4l4flVb1WVHvJ8KNAM/view?usp=drive [...] Format de la ressource électronique : Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=28008
in INTERNATIONAL POLYMER PROCESSING > Vol. XXXII, N° 1 (03/2017) . - p. 121-128[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 18732 - Périodique Bibliothèque principale Documentaires Disponible Development of a hybrid solid-microcellular co-injection molding process / Lih-Sheng Turng in INTERNATIONAL POLYMER PROCESSING, Vol. XIX, N° 1 (03/2004)
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Titre : Development of a hybrid solid-microcellular co-injection molding process Type de document : texte imprimé Auteurs : Lih-Sheng Turng, Auteur ; H. Kharbas, Auteur Année de publication : 2004 Article en page(s) : p. 77-86 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 668.9 Polymères Résumé : This paper presents the development of a hybrid solid-micro-cellular co-injection molding process that combines aesthetic and processing advantages of injection molding with benefits and property attributes of microcellular plastics (MCPs). A two-color injection molding machine has been modified and equipped with an interfacial platen and a supercritical fluid (SCF) unit for co-injection molding with regular resins and MCPs. Co-injection molded polystyrene (PS) parts with a microcellular core encapsulated by the solid skin layer have been successfully produced. Systematic experiments were carried out with solid-microcellular co-injection molding, conventional solid-solid co-injection molding, and regular microcellular injection molding processes to study the effects of process conditions and core/skin volume ratios on the penetration and morphology of the microcellular core. Light microscopy and scanning electron microscopy (SEM) of the solid-microcellular co-injection molded specimens reveal a microcellular core with fairly fine and uniform cell size of 8 to 12 microns and a cell density of up to 3x108cells/cm3. Under similar process conditions, microcellular cores were found to penetrate longer and generate a more uniform and thicker skin layer than do solid cores. While improving the surface finish with solid skin layers, this process is capable of producing parts with reduced sink marks, lighter part weights, and shorter cycle times. DOI : 10.3139/217.1806 En ligne : https://drive.google.com/file/d/1iPME4xSRxVs08fonLxfqi1ObduuE761u/view?usp=drive [...] Format de la ressource électronique : Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=3299
in INTERNATIONAL POLYMER PROCESSING > Vol. XIX, N° 1 (03/2004) . - p. 77-86[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 001027 - Périodique Bibliothèque principale Documentaires Disponible Effects of pressure and supercritical fluid on melt viscosity of LDPE in conventional and microcellular injection molding / C.-L. Hsu in INTERNATIONAL POLYMER PROCESSING, Vol. XXVII, N° 1 (03/2012)
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Titre : Effects of pressure and supercritical fluid on melt viscosity of LDPE in conventional and microcellular injection molding Type de document : texte imprimé Auteurs : C.-L. Hsu, Auteur ; Lih-Sheng Turng, Auteur ; Tim A. Osswald, Auteur ; N. Rudolph, Auteur ; E. Dougherty, Auteur ; P. Gorton, Auteur Année de publication : 2012 Article en page(s) : p. 18-24 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Cisaillement (mécanique)
Etat fondu (matériaux)
Fluides supercritiques
Matières plastiques -- Moulage par injection microcellulaire
Polyéthylène basse densité
Rhéologie
ViscositéIndex. décimale : 668.9 Polymères Résumé : In this study, the flow and rheological behaviors of low density polyethylene (LDPE) and single-phase LDPE/N2 polymer/gas solutions at various gas contents were measured using a highpressure slit-die rheometer. The resulting rheology data of LDPE and LDPE/N2 were curve fit using the Cross –WLF model to obtain the seven material model constants, which were then used in the simulation of conventional and microcellular injection molding processes. The pressure effect on the shear viscosity of LDPE was also studied. The pressure dependency coefficient, D3, in the Cross –WLF model was determined by the use of simulation to best fit the experimental results. In addition, a three-dimensional plot of shear viscosity as a function of shear rate and pressure at various temperatures was constructed. Based on this three-dimensional viscosity – shear rate– temperature – pressure plot, the increase in viscosity due to the pressure effect was found to be more profound at high pressures, low temperatures, and low shear rates. Note de contenu : - PREVIOUS WORK
- EXPERIMENTAL : Slit-die rheometer - Geometric modeling for simulation - Material - Process conditions
- RESULTS AND DISCUSSION : Experimental data for neat LDPE - Temperature distribution from simulation - Viscosity pressure dependency coefficient - Experiments of LDPE/N2 solutionsDOI : 10.3139/217.2493 En ligne : https://drive.google.com/file/d/1ptY25lrbTScWYVnA8HNll5ohpIKmktDX/view?usp=drive [...] Format de la ressource électronique : Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=13717
in INTERNATIONAL POLYMER PROCESSING > Vol. XXVII, N° 1 (03/2012) . - p. 18-24[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 13722 - Périodique Bibliothèque principale Documentaires Disponible Fabrication and characterization of electrospun thermoplastic polyurethane/fibroin small-diameter vascular grafts for vascular tissue engineering / E. Yu in INTERNATIONAL POLYMER PROCESSING, Vol. XXXI, N° 5 (11/2016)
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Titre : Fabrication and characterization of electrospun thermoplastic polyurethane/fibroin small-diameter vascular grafts for vascular tissue engineering Type de document : texte imprimé Auteurs : E. Yu, Auteur ; J. Zhang, Auteur ; J. A. Thomson, Auteur ; Lih-Sheng Turng, Auteur Année de publication : 2016 Article en page(s) : p. 638-646 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Cellules -- Cultures et milieux de culture
Electrofilature
Fourier, Spectroscopie infrarouge à transformée de
Ingénierie tissulaire
Polymères en chirurgie
Polymères en médecine
Polyuréthanes
Protéines végétales
Prothèses
Prothèses vasculaires
Soie et constituants
Technologie médicale
Textiles et tissus à usages médicaux
Textiles et tissus à usages techniques
Textiles et tissus à usages techniques -- Propriétés mécaniquesIndex. décimale : 668.4 Plastiques, vinyles Résumé : The demand for small-diameter blood vessel substitutes has been increasing due to a shortage of autograft vessels and problems with thrombosis and intimal hyperplasia with synthetic grafts. In this study, hybrid small-diameter vascular grafts made of thermoplastic polyurethane (TPU) and silk fibroin, which possessed a hybrid fibrous structure of an aligned inner layer and a random outer layer, were fabricated by the electrospinning technique using a customized striated collector that generated both aligned and random fibers simultaneously. A methanol post-treatment process induced the transition of fibroin protein conformation from the water-soluble, amorphous, and less ordered structures to the water-insoluble ?-sheet structures that possessed robust mechanical properties and relatively slow proteolytic degradation. The methanol post-treatment also created crimped fibers that mimicked the wavy structure of collagen fibers in natural blood vessels. Ultrafine nanofibers and nanowebs were found on the electrospun TPU/fibroin samples, which effectively increased the surface area for cell adhesion and migration. Cyclic circumferential tensile test results showed compatible mechanical properties for grafts made of a soft TPU/fibroin blend compared to human coronary arteries. In addition, cell culture tests with endothelial cells after 6 and 60 days of culture exhibited high cell viability and good biocompatibility of TPU/fibroin grafts, suggesting the potential of applying electrospun TPU/fibroin grafts in vascular tissue engineering. Note de contenu : - CELL CULTURE AND SEEDING
- RESULTS AND DISCUSSION : Fourier transform infrared spectroscopy - Structure and morphology - Mechanical properties - Cell culture resultsDOI : 10.3139/217.3247 En ligne : https://drive.google.com/file/d/194seUjb8XJD2n49MLWsSuLnGz-z9Vk8L/view?usp=drive [...] Format de la ressource électronique : Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=27401
in INTERNATIONAL POLYMER PROCESSING > Vol. XXXI, N° 5 (11/2016) . - p. 638-646[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 18491 - Périodique Bibliothèque principale Documentaires Disponible Injection molded solid and microcellular polylactide compounded with recycled paper shopping bag fibers / A. Kramschuster in INTERNATIONAL POLYMER PROCESSING, Vol. XXII, N° 5 (11/2007)
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Titre : Injection molded solid and microcellular polylactide compounded with recycled paper shopping bag fibers Type de document : texte imprimé Auteurs : A. Kramschuster, Auteur ; S. Pilla, Auteur ; S. Gong, Auteur ; A. Chandra, Auteur ; Lih-Sheng Turng, Auteur Année de publication : 2007 Article en page(s) : p. 436-445 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 668.9 Polymères Résumé : Recycled paper shopping bag fibers were melt-compounded using a batch mixer with biobased/biodegradable polylactide (PLA) at 10 and 30 wt.% using silane as a coupling agent. These PLA/fiber composites were then injection molded to produce both solid and microcellular tensile bars. The mechanical properties (specific modulus, specific tensile strength, specific toughness, and strain at break) of the neat PLA and PLA composites were tested and the cell morphology of the microcellular samples was examined using scanning electron microscopy. It was observed that the addition of the recycled paper shopping bag fibers resulted in an increase in cell density and decrease in average cell size for the microcellular components when compared with the neat PLA. The addition of the fibers increased the specific modulus of both solid and microcellular components, and high fiber contents (30 wt.%) resulted in an increase in specific tensile strength, yet yielded a decrease in the strain at break and specific toughness. The storage modulus was also improved with the addition of 10 and 30 wt.% fibers for both solid and microcellular components. DOI : 10.3139/217.2063 En ligne : https://drive.google.com/file/d/1SZj3Ywt82RoXbqqCzfNEw6FA2C-ft5Wm/view?usp=drive [...] Format de la ressource électronique : Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=2685
in INTERNATIONAL POLYMER PROCESSING > Vol. XXII, N° 5 (11/2007) . - p. 436-445[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 008361 - Périodique Bibliothèque principale Documentaires Disponible PermalinkMicrocellular injection molding / S. Gong in INTERNATIONAL POLYMER PROCESSING, Vol. XX, N° 2 (06/2005)
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PermalinkSingle and multi objective optimization for injection molding using numerical simulation with surrogate models and genetic algorithms / J. Zhou in INTERNATIONAL POLYMER PROCESSING, Vol. XXI, N° 5 (11/2006)
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PermalinkSolid and microcellular polylactide-carbon nanotube nanocomposites / S. Pilla in INTERNATIONAL POLYMER PROCESSING, Vol. XXII, N° 5 (11/2007)
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PermalinkStudy of microcellular injection molding with expandable thermoplastic microsphere / J. Peng in INTERNATIONAL POLYMER PROCESSING, Vol. XXVI, N° 3 (07/2011)
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PermalinkStudy of shrinkage and warpage in microcellular co-injection molding / C. Shen in INTERNATIONAL POLYMER PROCESSING, Vol. XXI, N° 4 (09/2006)
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