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Isothermal crystallization kinetics, morphology, and mechanical properties of biocomposites based on poly(3-hydroxybutyrate-co-4-hydroxybutyrate) and recycled carbon fiber / Hongyan Han in Industrial & engineering chemistry research, Vol. 51 N° 43 (Octobre 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 43 (Octobre 2012) . - pp. 14047-14060 Titre : Isothermal crystallization kinetics, morphology, and mechanical properties of biocomposites based on poly(3-hydroxybutyrate-co-4-hydroxybutyrate) and recycled carbon fiber Type de document : texte imprimé Auteurs : Hongyan Han, Auteur ; Xiaodong Wang, Auteur ; Dezhen Wu, Auteur Année de publication : 2013 Article en page(s) : pp. 14047-14060 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Carbon  fiber  Mechanical  properties  Morphology  Kinetics  Crystallization Résumé : The biocomposites of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3,4HB)] and recycled carbon fiber (RCF) were prepared via a melting extrusion. The crystallization behaviors and kinetics of the P(3,4HB) matrix in composites were exclusively studied under both nonisothermal and isothermal conditions. The corresponding results indicated that the P(3,4HB) either neat or compositing with RCF had a dual-peak cold crystallization behavior in the nonisothermal condition, and the isothermal crystallization rate of P(3,4HB) in composites was jointly determined by the rates of the nucleation and the crystal growth and integrity. However, it was reduced with the incorporation of RCF. Wide-angle X-ray scattering investigation demonstrated that the presence of RCF did not change the crystallization mechanism and crystalline structure of the P(3,4HB) matrix, but the crystallinity of the P(3,4HB) either neat or compositing with RCF was enhanced with an increase of crystallization temperature. Dynamic mechanical analysis revealed that the storage moduli of P(3,4HB)-based composites were significantly improved with increasing the RCF loadings, and the dual internal friction peaks corresponding to the thermal motion of surface molecule of crystalline zone and the glass transfer of whole macromolecules were observed on the thermograms of the P(3,4HB) either neat or compositing with RCF. The mechanical properties including tensile, flexural, and notched Izod impact strength were significantly improved in the presence of RCF, and such reinforcing and toughening effects were due to the good interfacial adhesion between RCF and P(3,4HB) as a result of bonding effect of silane coupling agent. Scanning electronic microscopy further confirmed a good dispersion of RCF in P(3,4HB) matrix and a strong interfacial interaction between fibers and matrix. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=26593332 [article] Isothermal crystallization kinetics, morphology, and mechanical properties of biocomposites based on poly(3-hydroxybutyrate-co-4-hydroxybutyrate) and recycled carbon fiber [texte imprimé] / Hongyan Han, Auteur ; Xiaodong Wang, Auteur ; Dezhen Wu, Auteur . - 2013 . - pp. 14047-14060. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 43 (Octobre 2012) . - pp. 14047-14060 Mots-clés : Carbon  fiber  Mechanical  properties  Morphology  Kinetics  Crystallization Résumé : The biocomposites of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3,4HB)] and recycled carbon fiber (RCF) were prepared via a melting extrusion. The crystallization behaviors and kinetics of the P(3,4HB) matrix in composites were exclusively studied under both nonisothermal and isothermal conditions. The corresponding results indicated that the P(3,4HB) either neat or compositing with RCF had a dual-peak cold crystallization behavior in the nonisothermal condition, and the isothermal crystallization rate of P(3,4HB) in composites was jointly determined by the rates of the nucleation and the crystal growth and integrity. However, it was reduced with the incorporation of RCF. Wide-angle X-ray scattering investigation demonstrated that the presence of RCF did not change the crystallization mechanism and crystalline structure of the P(3,4HB) matrix, but the crystallinity of the P(3,4HB) either neat or compositing with RCF was enhanced with an increase of crystallization temperature. Dynamic mechanical analysis revealed that the storage moduli of P(3,4HB)-based composites were significantly improved with increasing the RCF loadings, and the dual internal friction peaks corresponding to the thermal motion of surface molecule of crystalline zone and the glass transfer of whole macromolecules were observed on the thermograms of the P(3,4HB) either neat or compositing with RCF. The mechanical properties including tensile, flexural, and notched Izod impact strength were significantly improved in the presence of RCF, and such reinforcing and toughening effects were due to the good interfacial adhesion between RCF and P(3,4HB) as a result of bonding effect of silane coupling agent. Scanning electronic microscopy further confirmed a good dispersion of RCF in P(3,4HB) matrix and a strong interfacial interaction between fibers and matrix. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=26593332

Novel cyclolinear cyclotriphosphazene-linked epoxy resin for halogen-free fire resistance / Yongwei Bai in Industrial & engineering chemistry research, Vol. 51 N° 46 (Novembre 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 46 (Novembre 2012) . - pp. 15064-15074 Titre : Novel cyclolinear cyclotriphosphazene-linked epoxy resin for halogen-free fire resistance : Synthesis, characterization, and flammability characteristics Type de document : texte imprimé Auteurs : Yongwei Bai, Auteur ; Xiaodong Wang, Auteur ; Dezhen Wu, Auteur Année de publication : 2013 Article en page(s) : pp. 15064-15074 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Flammability  Fire  resistance Résumé : A novel halogen-free flame-retardant epoxy resin was designed by introducing phosphazene rings into the backbone in a cyclolinear-linked mode, and then it was synthesized through a three-step synthetic route. The chemical structures and compositions of all the cyclotriphosphazene precursors and the final product were confirmed by 1H and 31P NMR spectroscopy, elemental analysis, and Fourier transform infrared spectroscopy. The thermal curing behaviors of the synthesized epoxy resin with dicyandiamide, 4,4'-diaminodiphenylmethane, and novolak as hardeners were investigated by differential scanning calorimetry (DSC), and the thermal properties were also evaluated by DSC and thermogravimetric analysis. These thermosets achieved high glass transition temperatures over 150 °C and simultaneously displayed good thermal stability with high char yields. Moreover, these thermosets have higher tensile and flexural strength but lower impact toughness in comparison with the conventional epoxy thermosets. The flammability characteristics of the thermosets obtained by curing this epoxy with three hardeners were studied on the basis of the limiting oxygen index (LOI) and UL―94 vertical burning experiments as well as the analysis of residual chars of the tested bars after vertical burring. The high LOI values and the V―0 classification for these epoxy thermosets indicate that the incorporation of phosphazene rings into the molecular backbone imparts flame retardancy on the epoxy resin. This may result from a unique combination of phosphorus and nitrogen in the phosphazene ring. The epoxy resin synthesized in this study is a green functional polymer and may become a potential candidate for fire- and heat-resistant applications in electronic and microelectronic fields. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=26679625 [article] Novel cyclolinear cyclotriphosphazene-linked epoxy resin for halogen-free fire resistance : Synthesis, characterization, and flammability characteristics [texte imprimé] / Yongwei Bai, Auteur ; Xiaodong Wang, Auteur ; Dezhen Wu, Auteur . - 2013 . - pp. 15064-15074. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 46 (Novembre 2012) . - pp. 15064-15074 Mots-clés : Flammability  Fire  resistance Résumé : A novel halogen-free flame-retardant epoxy resin was designed by introducing phosphazene rings into the backbone in a cyclolinear-linked mode, and then it was synthesized through a three-step synthetic route. The chemical structures and compositions of all the cyclotriphosphazene precursors and the final product were confirmed by 1H and 31P NMR spectroscopy, elemental analysis, and Fourier transform infrared spectroscopy. The thermal curing behaviors of the synthesized epoxy resin with dicyandiamide, 4,4'-diaminodiphenylmethane, and novolak as hardeners were investigated by differential scanning calorimetry (DSC), and the thermal properties were also evaluated by DSC and thermogravimetric analysis. These thermosets achieved high glass transition temperatures over 150 °C and simultaneously displayed good thermal stability with high char yields. Moreover, these thermosets have higher tensile and flexural strength but lower impact toughness in comparison with the conventional epoxy thermosets. The flammability characteristics of the thermosets obtained by curing this epoxy with three hardeners were studied on the basis of the limiting oxygen index (LOI) and UL―94 vertical burning experiments as well as the analysis of residual chars of the tested bars after vertical burring. The high LOI values and the V―0 classification for these epoxy thermosets indicate that the incorporation of phosphazene rings into the molecular backbone imparts flame retardancy on the epoxy resin. This may result from a unique combination of phosphorus and nitrogen in the phosphazene ring. The epoxy resin synthesized in this study is a green functional polymer and may become a potential candidate for fire- and heat-resistant applications in electronic and microelectronic fields. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=26679625

Rapid In Situ Transesterification of Sunflower Oil / Jianli Zeng in Industrial & engineering chemistry research, Vol. 48 N°2 (Janvier 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N°2 (Janvier 2009) . - p. 850–856 Titre : Rapid In Situ Transesterification of Sunflower Oil Type de document : texte imprimé Auteurs : Jianli Zeng, Auteur ; Xiaodong Wang, Auteur ; Bing Zhao, Auteur ; Jingcan Sun, Auteur ; Yuchun Wang, Auteur Année de publication : 2009 Article en page(s) : p. 850–856 Note générale : chemical engineering Langues : Anglais (eng) Mots-clés : Sunflower  Oil--  Transesterification Résumé : A rapid in situ transesterification process of sunflower oil with methanol assisted by diethoxymethane (DEM) is described in this article. DEM served as both extraction solvent and reaction promoter in the process. The effects of moisture content of sunflower seeds, catalyst category, molar ratio of catalyst/oil, molar ratio of methanol/oil, molar ratio of DEM/oil, reaction time, reaction temperature, and agitation speed on the in situ transesterification were investigated. The most important factors which influenced the crude biodiesel yield, free fatty acid (FFA) content, and fatty acid methyl ester (FAME) purity were the molar ratio of DEM/oil, molar ratio of catalyst/oil, and molar ratio of catalyst/oil, respectively. An empirical model of the rapid in situ transesterification process was established and used to determine the optimal reaction conditions. When the in situ transesterification was carried out at the molar ratio of catalyst/oil of 0.5:1, the molar ratio of methanol/oil of 101.39:1, the molar ratio of DEM/oil of 57.85:1, the agitation speed of 150 rpm, and reaction temperature of 20 °C, a product containing 97.7% FAME and 0.74% FFA was obtained within 13 min. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8008956 [article] Rapid In Situ Transesterification of Sunflower Oil [texte imprimé] / Jianli Zeng, Auteur ; Xiaodong Wang, Auteur ; Bing Zhao, Auteur ; Jingcan Sun, Auteur ; Yuchun Wang, Auteur . - 2009 . - p. 850–856. chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N°2 (Janvier 2009) . - p. 850–856 Mots-clés : Sunflower  Oil--  Transesterification Résumé : A rapid in situ transesterification process of sunflower oil with methanol assisted by diethoxymethane (DEM) is described in this article. DEM served as both extraction solvent and reaction promoter in the process. The effects of moisture content of sunflower seeds, catalyst category, molar ratio of catalyst/oil, molar ratio of methanol/oil, molar ratio of DEM/oil, reaction time, reaction temperature, and agitation speed on the in situ transesterification were investigated. The most important factors which influenced the crude biodiesel yield, free fatty acid (FFA) content, and fatty acid methyl ester (FAME) purity were the molar ratio of DEM/oil, molar ratio of catalyst/oil, and molar ratio of catalyst/oil, respectively. An empirical model of the rapid in situ transesterification process was established and used to determine the optimal reaction conditions. When the in situ transesterification was carried out at the molar ratio of catalyst/oil of 0.5:1, the molar ratio of methanol/oil of 101.39:1, the molar ratio of DEM/oil of 57.85:1, the agitation speed of 150 rpm, and reaction temperature of 20 °C, a product containing 97.7% FAME and 0.74% FFA was obtained within 13 min. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8008956