The Experts below are selected from a list of 24423 Experts worldwide ranked by ideXlab platform
Robert C Haddon - One of the best experts on this subject based on the ideXlab platform.
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chemical engineering of the single walled carbon nanotube nylon 6 interface
Journal of the American Chemical Society, 2006Co-Authors: Bin Zhao, Mikhail E Itkis, Elena Bekyarova, Hui Hu, Verina Kranak, And Aiping Yu, Robert C HaddonAbstract:We report an approach to the chemical engineering of the single-walled carbon nanotube (SWNT)−polymer interfacial interaction in a nylon 6 graft copolymer composite which is based on the degree of SWNT functionality. Continuous fibers are drawn from composites fabricated from the in situ Polymerization of caprolactam with SWNTs possessing a range of carboxylic acid (SWNT-COOH) and amide (SWNT-CONH2) functionalities. Mechanical performance evaluation of the composite fibers shows that a high concentration of the carboxylic acid functional groups leads to a stronger SWNT−nylon interfacial interaction, as reflected in greater values of the Young's modulus and mechanical strength. Replacement of the COOH group by CONH2 in the SWNT starting material changes the Grafting Polymerization chemistry, thereby leading to the covalent attachment of longer graft copolymer chains to the SWNTs, and alters the composite morphology while increasing the composite flexibility and toughness.
Yadira I. Vega-cantú - One of the best experts on this subject based on the ideXlab platform.
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Polystyrene composites with very high carbon nanotubes loadings by in situ Grafting Polymerization
Journal of Materials Research, 2013Co-Authors: Claudia G. Espinosa-gonzález, Fernando J. Rodríguez-macías, Abraham G. Cano-márquez, Jasmeet Kaur, Meisha L. Shofner, Yadira I. Vega-cantúAbstract:We introduce a novel method for producing polystyrene (PS)-grafted multiwalled carbon nanotubes (MWCNTs), which provides a direct route to composites where carbon nanotubes (CNTs) are the major component. Infrared and Raman spectroscopies confirmed that the MWCNTs were functionalized with PS. Thermogravimetric analysis showed that CNTs increase thermal stability of the composite up to a critical loading (∼40 wt%) beyond which high nanotube loadings decrease the polymer degradation temperature, as a consequence of the thermal properties of CNTs and the composite morphology. Even at loadings as high as 80 wt% MWCNTs, the composite is an effective masterbatch material for both solution- and melt-processing. These results show that in situ Polymerizations can be flexible and robust techniques for nanocomposite processing, overcoming limitations of conventional processing techniques to produce nanocomposites with very high nanotube loadings, not achieved hitherto.
Xiabin Jing - One of the best experts on this subject based on the ideXlab platform.
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a novel approach to Grafting Polymerization of e caprolactone onto starch granules
Carbohydrate Polymers, 2005Co-Authors: Li Chen, Xinchao Bian, Xueyu Qiu, Xiuli Zhuang, Xuesi Chen, Xiabin JingAbstract:Abstract A new biodegradable starch graft-copolymer, starch-g-poly(e-caprolatone) (St-g-PCL), was synthesized in situ by the ring-opening graft-Polymerization of a e-caprolactone (CL) monomer onto starch granules in the presence of Sn(Oct)2. The Polymerization was carried out in three different Polymerization methods: in bulk, in toluene suspension or in suspension/bulk Polymerization, where a suspension/bulk process resulted in highest PCL Grafting efficiency in 40 wt%. The structure of St-g-PCL was characterized by IR, DSC, SEM and WAXD. Both of the CL monomer and amylose corn starch were of industrial grade, without further purifications. The medium-resistance of St-g-PCL and the mechanical properties of the PCL composite blending with St-g-PCL were better than that of the PCL/starch blending composite.
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hydroxyapatite surface modified by l lactic acid and its subsequent Grafting Polymerization of l lactide
Biomacromolecules, 2005Co-Authors: Xueyu Qiu, Li Chen, Xuesi Chen, Zhongkui Hong, Xiabin JingAbstract:A new method of surface modification of hydroxyapatite nanoparticles (n-HA) by surface Grafting reaction of l-lactic acid and ring-opening Polymerization of l-lactide (LLA) was developed. Two modified HA nanoparticles were obtained: HA modified by l-lactic acid (l-HA) and HA Grafting with poly(l-lactide) (PLLA; p-HA). The modified surface of n-HA was attested by Fourier transformation infrared, 31P MAS NMR, and thermal gravimetric analysis. The results showed that l-lactic acid could be easily grafted onto the n-HA surface by forming a Ca carboxylate bond and initiated by the hydroxyl group of the grafted l-lactic acid and LLA could be graft-polymerized onto the n-HA surface in the presence of stannous octanoate. The highest Grafting amounts of l-lactic acid and PLLA were about 33 and 22 wt %, respectively. The modified HA/PLLA composites showed good mechanical properties and uniform microstructure. The tensile strength and modulus of the p-HA/PLLA composite containing 15 wt % of p-HA were 67 MPa and 2.1...
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Grafting Polymerization of l lactide on the surface of hydroxyapatite nano crystals
Polymer, 2004Co-Authors: Zhongkui Hong, Xueyu Qiu, Xuesi Chen, Jingru Sun, Mingxiao Deng, Xiabin JingAbstract:A novel method of Grafting ring-opening Polymerization of L-lactide (LLA) onto the surface of hydroxyapatite nano-particles (n-HAP) was developed. PLLA was directly connected onto the HAP surface through a chemical linkage. The PLLA-g-HAP particles could be stably dispersed in organic solvent such as chloroform for several weeks. The n-HAP particles still retained the original dimension and shape after the Grafting of PLLA. Compared with the P-31 MAS-NMR spectrum of pure HAP powders, there appeared a downfield displacement of 1.2 ppm in the spectrum of PLLA-g-HAP. Fourier transformation infrared (FT-IR) spectra further confirmed the existence of PLLA on the surface of PLLA-g-HAP. The amount of grafted polymer determined by thermal gravimetric analysis (TGA) was about 6% in weight. The tensile strength and elongation at break of the PLLA/PLLA-g-HAP composite containing 8 wt% of PLLA-g-HAP were 55 MPa and about 10-13%, respectively, while those of the PLLA/n-HAP composites were 40 MPa and 3-5%, respectively.
Bin Zhao - One of the best experts on this subject based on the ideXlab platform.
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chemical engineering of the single walled carbon nanotube nylon 6 interface
Journal of the American Chemical Society, 2006Co-Authors: Bin Zhao, Mikhail E Itkis, Elena Bekyarova, Hui Hu, Verina Kranak, And Aiping Yu, Robert C HaddonAbstract:We report an approach to the chemical engineering of the single-walled carbon nanotube (SWNT)−polymer interfacial interaction in a nylon 6 graft copolymer composite which is based on the degree of SWNT functionality. Continuous fibers are drawn from composites fabricated from the in situ Polymerization of caprolactam with SWNTs possessing a range of carboxylic acid (SWNT-COOH) and amide (SWNT-CONH2) functionalities. Mechanical performance evaluation of the composite fibers shows that a high concentration of the carboxylic acid functional groups leads to a stronger SWNT−nylon interfacial interaction, as reflected in greater values of the Young's modulus and mechanical strength. Replacement of the COOH group by CONH2 in the SWNT starting material changes the Grafting Polymerization chemistry, thereby leading to the covalent attachment of longer graft copolymer chains to the SWNTs, and alters the composite morphology while increasing the composite flexibility and toughness.
Claudia G. Espinosa-gonzález - One of the best experts on this subject based on the ideXlab platform.
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Polystyrene composites with very high carbon nanotubes loadings by in situ Grafting Polymerization
Journal of Materials Research, 2013Co-Authors: Claudia G. Espinosa-gonzález, Fernando J. Rodríguez-macías, Abraham G. Cano-márquez, Jasmeet Kaur, Meisha L. Shofner, Yadira I. Vega-cantúAbstract:We introduce a novel method for producing polystyrene (PS)-grafted multiwalled carbon nanotubes (MWCNTs), which provides a direct route to composites where carbon nanotubes (CNTs) are the major component. Infrared and Raman spectroscopies confirmed that the MWCNTs were functionalized with PS. Thermogravimetric analysis showed that CNTs increase thermal stability of the composite up to a critical loading (∼40 wt%) beyond which high nanotube loadings decrease the polymer degradation temperature, as a consequence of the thermal properties of CNTs and the composite morphology. Even at loadings as high as 80 wt% MWCNTs, the composite is an effective masterbatch material for both solution- and melt-processing. These results show that in situ Polymerizations can be flexible and robust techniques for nanocomposite processing, overcoming limitations of conventional processing techniques to produce nanocomposites with very high nanotube loadings, not achieved hitherto.
