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37 results on '"Gómez, Marian"'

12. Educación, políticas públicas y cultura.

Author

Mendoza Gómez, Marian

Abstract

Copyright of Clivajes - Revista de Ciencias Sociales is the property of Universidad Veracruzana and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Published
2020
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14. The crystallization of polypropylene in multiwall carbon nanotube-based composites

Author

European Commission, Ministerio de Ciencia, Innovación y Universidades (España), Marco, C., Naffakh, Mohammed, Gómez, Marian C., Santoro, Gonzalo, Ellis, Gary James, European Commission, Ministerio de Ciencia, Innovación y Universidades (España), Marco, C., Naffakh, Mohammed, Gómez, Marian C., Santoro, Gonzalo, and Ellis, Gary James

Abstract

The crystallization process of isotactic polypropylene (iPP) was studied under both dynamic and isothermal conditions for a series of multiwall carbon nanotube (MWCNT) composites with nanotube concentrations between 0.1 and 1.0% by weight. The nucleation activity of the nanofillers was confirmed for both dynamic and isothermal crystallization, and was shown to be composition dependent. The effect of the nanofiller on the crystallization of iPP was discussed using the temperature coefficients obtained to determine the interfacial free energy and free energy of nucleation. The basal interfacial free energy decreased with respect to that of neat iPP by up to 15% for as little as 0.1% MWCNT, subsequently decreasing linearly with increasing nanotube concentration. This behavior is in line with the crystallization behavior of iPP with conventional nucleating agents.

Published
2011

15. A solvent-free dispersion method for the preparation of PET/MWCNT composites

Author

Ministerio de Ciencia e Innovación (España), Santoro, Gonzalo, Gómez, Marian A., Marco, Carlo, Ellis, Gary James, Ministerio de Ciencia e Innovación (España), Santoro, Gonzalo, Gómez, Marian A., Marco, Carlo, and Ellis, Gary James

Abstract

A simple, easily accessible solvent-free method for the dispersion of MWCNTs into PET is proposed, based on the preparation of a microparticulate polymer/nanotube masterbatch via cryogenic impact-milling and its subsequent melt blending with the bulk polymer. Thermal and mechanical properties of nanocomposites prepared using this method were evaluated as a function of nanotube concentration. Thermal stability was improved, and superior crystallization behavior of PET in the nanocomposites was observed. Significant improvements of around 25% in tensile strength and tensile modulus of the nanocomposites was achieved using this strategy, with only 0.25 wt.-% MWCNT, compared to previous literature data where 1 wt.-% MWCNT was employed.

Published
2010

37. Solvent-free preparation of high-toughness epoxy--SWNT composite materials.

Author

González-Domínguez JM, Ansón-Casaos A, Díez-Pascual AM, Ashrafi B, Naffakh M, Backman D, Stadler H, Johnston A, Gómez M, and Martínez MT

Abstract

Multicomponent nanocomposite materials based on a high-performance epoxy system and single-walled carbon nanotubes (SWNTs) have been prepared. The noncovalent wrapping of nitric acid-treated SWNTs with a PEO-based amphiphilic block copolymer leads to a highly disaggregated filler with a boosted miscibility in the epoxy matrix, allowing its dispersion without organic solvents. Although direct dispersion of acid-treated SWNTs results in modestly improved epoxy matrix mechanical properties, the incorporation of wrapped SWNTs produces a huge increase in toughness (276% improvement at 0.5 wt % loading) and impact strength (193% at 0.5 wt % loading) with no detrimental effect on the elastic properties. A synergistic effect between SWNTs and the block copolymer is revealed on the basis of tensile and impact strength results. Atomic force microscopy has been applied, obtaining stiffness mappings that identify nanostructure features responsible of the dynamic mechanical behavior. The electrical percolation threshold is greatly reduced, from 0.31 to 0.03 wt % SWNTs when block copolymer-wrapped SWNTs are used, and all the measured conductivity values increased up to a maximum of 7 orders of magnitude with respect to the baseline matrix (1 wt % wrapped-SWNTs loading). This approach provides an efficient way to disperse barely dispersible SWNTs without solvents into an epoxy matrix, and to generate substantial improvements with small amounts of SWNTs.

Published
2011
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