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Shear viscosity of CO2-plasticized polystyrene under high static pressures / Maxwell J. Wingert in Industrial & engineering chemistry research, Vol. 48 N° 11 (Juin 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 11 (Juin 2009) . - pp. 5460–5471 Titre : Shear viscosity of CO2-plasticized polystyrene under high static pressures Type de document : texte imprimé Auteurs : Maxwell J. Wingert, Auteur ; Shunahshep Shukla, Auteur ; Kurt W. Koelling, Auteur Année de publication : 2009 Article en page(s) : pp. 5460–5471 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Shear  viscosity  measurements  Polymer/supercritical  fluid  systems  Pressure Résumé : High-pressure shear viscosity measurements of polymer/supercritical fluid systems are numerous, but most involve pressure-gradient equipment such as a capillary or slit die with pressure drops exceeding 10%. Pressure change across the measurement region introduces some errors when quantifying the effect of blowing agents and other diluents on viscosity. This source of errors was removed by using a static-pressure, Couette rheometer. The viscosity of polystyrene (PS)/carbon dioxide (CO2) was measured from 140 to 180 °C and from 3 to 6 wt % CO2. The effect of pressure on diluent-free PS viscosity was required to calculate the CO2 concentration shift factor. Thus, viscosities at both atmospheric and elevated pressure (via helium, an insoluble gas) were measured using the same equipment and method. The Fillers−Moonan−Tschoegl (FMT) model was overdefined for obtaining free volume parameters, but it was a helpful correlation tool to obtain the pressure effect on viscosity. Pressure and concentration shift factors obtained from the experiments were compared with empirical free-volume plasticization models, one based on glass transition temperature, the other on P−V−T behavior. Unfortunately, neither model demonstrated quantitative agreement with the experimental data within the 3−6 wt % CO2 range examined. The WLF−Chow model, based on Tg data, fared better than the P−V−T-based model. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800896r [article] Shear viscosity of CO2-plasticized polystyrene under high static pressures [texte imprimé] / Maxwell J. Wingert, Auteur ; Shunahshep Shukla, Auteur ; Kurt W. Koelling, Auteur . - 2009 . - pp. 5460–5471. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 11 (Juin 2009) . - pp. 5460–5471 Mots-clés : Shear  viscosity  measurements  Polymer/supercritical  fluid  systems  Pressure Résumé : High-pressure shear viscosity measurements of polymer/supercritical fluid systems are numerous, but most involve pressure-gradient equipment such as a capillary or slit die with pressure drops exceeding 10%. Pressure change across the measurement region introduces some errors when quantifying the effect of blowing agents and other diluents on viscosity. This source of errors was removed by using a static-pressure, Couette rheometer. The viscosity of polystyrene (PS)/carbon dioxide (CO2) was measured from 140 to 180 °C and from 3 to 6 wt % CO2. The effect of pressure on diluent-free PS viscosity was required to calculate the CO2 concentration shift factor. Thus, viscosities at both atmospheric and elevated pressure (via helium, an insoluble gas) were measured using the same equipment and method. The Fillers−Moonan−Tschoegl (FMT) model was overdefined for obtaining free volume parameters, but it was a helpful correlation tool to obtain the pressure effect on viscosity. Pressure and concentration shift factors obtained from the experiments were compared with empirical free-volume plasticization models, one based on glass transition temperature, the other on P−V−T behavior. Unfortunately, neither model demonstrated quantitative agreement with the experimental data within the 3−6 wt % CO2 range examined. The WLF−Chow model, based on Tg data, fared better than the P−V−T-based model. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800896r