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Fabrication of polylactide / poly (ε - caprolactone) blend fibers by electrospinning / Liangliang Lu in Industrial & engineering chemistry research, Vol. 51 N° 9 (Mars 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 9 (Mars 2012) . - pp. 3682–3691 Titre : Fabrication of polylactide / poly (ε - caprolactone) blend fibers by electrospinning : Morphology and orientation Type de document : texte imprimé Auteurs : Liangliang Lu, Auteur ; Defeng Wu, Auteur ; Ming Zhang, Auteur Année de publication : 2012 Article en page(s) : pp. 3682–3691 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Fiber  Polylactide Résumé : Randomly oriented fiber mats and well-aligned fiber bundles of the biodegradable polylactide (PLA)/poly(ε-caprolactone) (PCL) blends were successfully produced by electrospinning in the present study. For the reticulate fibers, the effects of the blending ratio of two polymers and compositions of mixed solvents on fiber morphology were investigated. The results reveal that the fibers with lower PCL mass fraction show better morphology with larger average fiber diameter than those of the fibers with higher PCL mass fraction. Besides, a small addition of dimethylformamide (DMF) as the assistant solvent favors further improvement of fiber morphology because of the synergistic effects by improved conductivity and altered viscosity of the electrospun solutions. Although the as-obtained blend fibers show smooth surface structure, the phase separation between PCL and PLA occurs inside the fibers because the two components are thermodynamically immiscible, and the discrete phase shows an elongated morphology along with the fiber axis, instead of the droplet structure. For the aligned fiber bundles collected on a rotating disk, the degree of order increases with increase of the tangential velocity, accompanied by reduced average fiber diameter. Hierarchical orientations including the macroscopic fiber alignment, the elongation of discrete PCL phase, and the molecular orientation of both the PLA and PCL can be observed within the aligned blend fibers. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie2028969 [article] Fabrication of polylactide / poly (ε - caprolactone) blend fibers by electrospinning : Morphology and orientation [texte imprimé] / Liangliang Lu, Auteur ; Defeng Wu, Auteur ; Ming Zhang, Auteur . - 2012 . - pp. 3682–3691. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 9 (Mars 2012) . - pp. 3682–3691 Mots-clés : Fiber  Polylactide Résumé : Randomly oriented fiber mats and well-aligned fiber bundles of the biodegradable polylactide (PLA)/poly(ε-caprolactone) (PCL) blends were successfully produced by electrospinning in the present study. For the reticulate fibers, the effects of the blending ratio of two polymers and compositions of mixed solvents on fiber morphology were investigated. The results reveal that the fibers with lower PCL mass fraction show better morphology with larger average fiber diameter than those of the fibers with higher PCL mass fraction. Besides, a small addition of dimethylformamide (DMF) as the assistant solvent favors further improvement of fiber morphology because of the synergistic effects by improved conductivity and altered viscosity of the electrospun solutions. Although the as-obtained blend fibers show smooth surface structure, the phase separation between PCL and PLA occurs inside the fibers because the two components are thermodynamically immiscible, and the discrete phase shows an elongated morphology along with the fiber axis, instead of the droplet structure. For the aligned fiber bundles collected on a rotating disk, the degree of order increases with increase of the tangential velocity, accompanied by reduced average fiber diameter. Hierarchical orientations including the macroscopic fiber alignment, the elongation of discrete PCL phase, and the molecular orientation of both the PLA and PCL can be observed within the aligned blend fibers. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie2028969

Rheological percolation behavior and isothermal crystallization of poly(butyene Succinte)/carbon nanotube composites / Lijuan Yuan in Industrial & engineering chemistry research, Vol. 50 N° 24 (Décembre 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 24 (Décembre 2011) . - pp. 14186-14192 Titre : Rheological percolation behavior and isothermal crystallization of poly(butyene Succinte)/carbon nanotube composites Type de document : texte imprimé Auteurs : Lijuan Yuan, Auteur ; Defeng Wu, Auteur ; Ming Zhang, Auteur Année de publication : 2012 Article en page(s) : pp. 14186-14192 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Composite  material  Crystallization Résumé : Carbon nanotube (CNT) filled poly(butylene succinate) composites (PBSCNs) were prepared by melt compounding. The oscillatory rheological properties and crystallization behavior and kinetics were then investigated. The results show that the percolation network of CNTs in the small amplitude oscillatory shear flow is temperature dependent and the values of percolation thresholds reduce gradually with an increase of temperature. Therefore, the principle of time-temperature superposition is invalid on the dynamic rheological responses of those percolated PBSCNs. Besides, the presence of CNTs highly promotes the crystallization of PBS, increasing the overall crystallization rate. But the nucleation mechanism of PBS is not altered with addition of CNTs because the PBS itself is nucleated heterogeneously. DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=25299889 [article] Rheological percolation behavior and isothermal crystallization of poly(butyene Succinte)/carbon nanotube composites [texte imprimé] / Lijuan Yuan, Auteur ; Defeng Wu, Auteur ; Ming Zhang, Auteur . - 2012 . - pp. 14186-14192. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 24 (Décembre 2011) . - pp. 14186-14192 Mots-clés : Composite  material  Crystallization Résumé : Carbon nanotube (CNT) filled poly(butylene succinate) composites (PBSCNs) were prepared by melt compounding. The oscillatory rheological properties and crystallization behavior and kinetics were then investigated. The results show that the percolation network of CNTs in the small amplitude oscillatory shear flow is temperature dependent and the values of percolation thresholds reduce gradually with an increase of temperature. Therefore, the principle of time-temperature superposition is invalid on the dynamic rheological responses of those percolated PBSCNs. Besides, the presence of CNTs highly promotes the crystallization of PBS, increasing the overall crystallization rate. But the nucleation mechanism of PBS is not altered with addition of CNTs because the PBS itself is nucleated heterogeneously. DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=25299889

Rheology of carbon nanotubes – filled poly(vinylidene fluoride) composites / Defeng Wu in Industrial & engineering chemistry research, Vol. 51 N° 19 (Mai 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 19 (Mai 2012) . - pp. 6705–6713 Titre : Rheology of carbon nanotubes – filled poly(vinylidene fluoride) composites Type de document : texte imprimé Auteurs : Defeng Wu, Auteur ; Jianghong Wang, Auteur ; Ming Zhang, Auteur Année de publication : 2012 Article en page(s) : pp. 6705–6713 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Rheology  Carbon  nanotubes Résumé : The carbon nanotubes (CNTs)–filled poly(vinylidene fluoride) (PVDF) composites (PCTs) were prepared by melt compounding for rheological study. The steady and oscillatory flow behaviors were then explored. The results show that the presence of CNTs enhances the pseudoplastic flow accompanied by the increased flow activation energy. However, the linear flow region is not sensitive to the temperature whether driven by shear rate or by strain. During oscillatory shear flow, the solid-like response is attributed to the percolation of CNTs, but the formation of a percolated CNT network is temperature-dependent, and the percolation threshold values reduce with an increase of temperature. The two-phase viscoelastic model was then used to further describe the linear responses of composites, aiming at relating hierarchical structures of the CNTs to flow behaviors of the composites. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie2024454 [article] Rheology of carbon nanotubes – filled poly(vinylidene fluoride) composites [texte imprimé] / Defeng Wu, Auteur ; Jianghong Wang, Auteur ; Ming Zhang, Auteur . - 2012 . - pp. 6705–6713. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 19 (Mai 2012) . - pp. 6705–6713 Mots-clés : Rheology  Carbon  nanotubes Résumé : The carbon nanotubes (CNTs)–filled poly(vinylidene fluoride) (PVDF) composites (PCTs) were prepared by melt compounding for rheological study. The steady and oscillatory flow behaviors were then explored. The results show that the presence of CNTs enhances the pseudoplastic flow accompanied by the increased flow activation energy. However, the linear flow region is not sensitive to the temperature whether driven by shear rate or by strain. During oscillatory shear flow, the solid-like response is attributed to the percolation of CNTs, but the formation of a percolated CNT network is temperature-dependent, and the percolation threshold values reduce with an increase of temperature. The two-phase viscoelastic model was then used to further describe the linear responses of composites, aiming at relating hierarchical structures of the CNTs to flow behaviors of the composites. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie2024454