Documents disponibles écrits par cet auteur

Influence of nanoclay concentration on the CO2 diffusion and physical properties of PMMA montmorillonite microcellular foams / Vera Realinho 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. 13819–13824 Titre : Influence of nanoclay concentration on the CO2 diffusion and physical properties of PMMA montmorillonite microcellular foams Type de document : texte imprimé Auteurs : Vera Realinho, Auteur ; Marcelo Antunes, Auteur ; Antonio B. Martinez, Auteur Année de publication : 2012 Article en page(s) : pp. 13819–13824 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Nanoclay  concentration  Microcellular  foams Résumé : Microcellular foams of poly(methyl methacrylate) with variable concentrations of an organically modified montmorillonite, oMMT (2.5–10 wt %), were prepared using a supercritical CO2 dissolution physical foaming process. Particular importance was given to the analysis of the influence of the montmorillonite on the CO2 desorption behavior out of the several nanocomposites. The saturation concentration of CO2 was found to be two times higher in the nanocomposites when compared to the pure PMMA and a comparative analysis of the desorption curves showed that a higher concentration of CO2 remained in the nanocomposites for long times when compared to PMMA, except for the 10 wt % oMMT nanocomposite. Also, the incorporation of oMMT promoted the formation of submicrometric foams with much lower cell sizes and higher cell densities. With increasing the amount of oMMT, the glass transition temperature of PMMA decreased in both the solids and foams and important improvements were observed regarding the specific elastic moduli of the foams, demonstrating the mechanical reinforcement effect of oMMT. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie201532h [article] Influence of nanoclay concentration on the CO2 diffusion and physical properties of PMMA montmorillonite microcellular foams [texte imprimé] / Vera Realinho, Auteur ; Marcelo Antunes, Auteur ; Antonio B. Martinez, Auteur . - 2012 . - pp. 13819–13824. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 24 (Décembre 2011) . - pp. 13819–13824 Mots-clés : Nanoclay  concentration  Microcellular  foams Résumé : Microcellular foams of poly(methyl methacrylate) with variable concentrations of an organically modified montmorillonite, oMMT (2.5–10 wt %), were prepared using a supercritical CO2 dissolution physical foaming process. Particular importance was given to the analysis of the influence of the montmorillonite on the CO2 desorption behavior out of the several nanocomposites. The saturation concentration of CO2 was found to be two times higher in the nanocomposites when compared to the pure PMMA and a comparative analysis of the desorption curves showed that a higher concentration of CO2 remained in the nanocomposites for long times when compared to PMMA, except for the 10 wt % oMMT nanocomposite. Also, the incorporation of oMMT promoted the formation of submicrometric foams with much lower cell sizes and higher cell densities. With increasing the amount of oMMT, the glass transition temperature of PMMA decreased in both the solids and foams and important improvements were observed regarding the specific elastic moduli of the foams, demonstrating the mechanical reinforcement effect of oMMT. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie201532h

Microcellular foaming of layered double hydroxide−polymer nanocomposites / Antonio B. Martinez in Industrial & engineering chemistry research, Vol. 50 N° 9 (Mai 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 9 (Mai 2011) . - pp. 5239–5247 Titre : Microcellular foaming of layered double hydroxide−polymer nanocomposites Type de document : texte imprimé Auteurs : Antonio B. Martinez, Auteur ; Vera Realinho, Auteur ; Marcelo Antunes, Auteur Année de publication : 2011 Article en page(s) : pp. 5239–5247 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Nanocomposites  Microcellular Résumé : Microcellular foams of polystyrene (PS), poly(styrene-co-acrylonitrile) (SAN), and poly(methyl methacrylate) (PMMA) having organically modified layered double hydroxides (LDH) were prepared using a high-pressure CO2 dissolution foaming process and characterized both structurally and thermo-mechanically. The saturation concentration of CO2 was found to increase with the incorporation of LDH nanoparticles into the PMMA, while the opposite effect was observed in the PS and SAN nanocomposites with respect to the pure polymers. The CO2 desorption diffusion coefficient substantially decreased in the nanocomposites comparatively to the respective pure polymers. The incorporation of hydrotalcite (HT) into the polymers and subsequent foaming resulted in foams with finer and more isotropic cellular structures, related to a cell nucleation effect promoted by the particles. No significant differences were found among the several foamed nanocomposites. Both PS and SAN nanocomposite foams displayed higher glass transition temperatures than the respective unfilled ones, related to a higher amount of residual CO2 in the last, favoring plasticization. The contrary effect was observed in PMMA, attributed to a combined plasticizing effect promoted by the higher affinity of PMMA for CO2 and greater interaction with the organically modified HT platelets. Although no significant differences were found among the several nanocomposite foams and respective unfilled counterparts, the incorporation of HT limited the reduction observed in the specific storage moduli with foaming, related to a finer cellular structure induced by the HT particles. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie101375f [article] Microcellular foaming of layered double hydroxide−polymer nanocomposites [texte imprimé] / Antonio B. Martinez, Auteur ; Vera Realinho, Auteur ; Marcelo Antunes, Auteur . - 2011 . - pp. 5239–5247. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 9 (Mai 2011) . - pp. 5239–5247 Mots-clés : Nanocomposites  Microcellular Résumé : Microcellular foams of polystyrene (PS), poly(styrene-co-acrylonitrile) (SAN), and poly(methyl methacrylate) (PMMA) having organically modified layered double hydroxides (LDH) were prepared using a high-pressure CO2 dissolution foaming process and characterized both structurally and thermo-mechanically. The saturation concentration of CO2 was found to increase with the incorporation of LDH nanoparticles into the PMMA, while the opposite effect was observed in the PS and SAN nanocomposites with respect to the pure polymers. The CO2 desorption diffusion coefficient substantially decreased in the nanocomposites comparatively to the respective pure polymers. The incorporation of hydrotalcite (HT) into the polymers and subsequent foaming resulted in foams with finer and more isotropic cellular structures, related to a cell nucleation effect promoted by the particles. No significant differences were found among the several foamed nanocomposites. Both PS and SAN nanocomposite foams displayed higher glass transition temperatures than the respective unfilled ones, related to a higher amount of residual CO2 in the last, favoring plasticization. The contrary effect was observed in PMMA, attributed to a combined plasticizing effect promoted by the higher affinity of PMMA for CO2 and greater interaction with the organically modified HT platelets. Although no significant differences were found among the several nanocomposite foams and respective unfilled counterparts, the incorporation of HT limited the reduction observed in the specific storage moduli with foaming, related to a finer cellular structure induced by the HT particles. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie101375f