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Rheology of poly(acrylic acid) / Yuchen Wang in Industrial & engineering chemistry research, Vol. 51 N° 50 (Décembre 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 50 (Décembre 2012) . - pp 16196–16208 Titre : Rheology of poly(acrylic acid) : A model study Type de document : texte imprimé Auteurs : Yuchen Wang, Auteur ; Richard A. Pethrick, Auteur ; Nicholas E. Hudson, Auteur Année de publication : 2013 Article en page(s) : pp 16196–16208 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Rheology Résumé : In this study, we examine the rheological characteristics of poly(acrylic acid) (PAA) polymers in aqueous solutions at 20 °C using various techniques. We also develop a model to simulate the rheological behavior of the polymer solutions, because, in some applications, the polymer is required to be dispersed within a short period of time, during which high-shear mixing is commonly used to achieve the necessary level of homogeneity. The model, which involves consideration of reptation, relaxation of the chains by slippage or loop relaxation, and normal Rouse dynamics, is appropriately adapted to reflect the structural changes of the polymer molecules and then used to identify possible relationships between molecular structure and viscoplastic behavior. The simple theory for flexible polymers is modified to include the possibility of complex formation by association between neighboring polymer molecules. We conclude that, although the model is sensitive to the average molar mass of the polymer, additional and more extensive high-shear-rate data are required to explore fully the validity of the Rouse description. However, the scaling of the viscosity by the addition of an increased friction factor provides a reasonable description of the short-range motions observed. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie302313a [article] Rheology of poly(acrylic acid) : A model study [texte imprimé] / Yuchen Wang, Auteur ; Richard A. Pethrick, Auteur ; Nicholas E. Hudson, Auteur . - 2013 . - pp 16196–16208. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 50 (Décembre 2012) . - pp 16196–16208 Mots-clés : Rheology Résumé : In this study, we examine the rheological characteristics of poly(acrylic acid) (PAA) polymers in aqueous solutions at 20 °C using various techniques. We also develop a model to simulate the rheological behavior of the polymer solutions, because, in some applications, the polymer is required to be dispersed within a short period of time, during which high-shear mixing is commonly used to achieve the necessary level of homogeneity. The model, which involves consideration of reptation, relaxation of the chains by slippage or loop relaxation, and normal Rouse dynamics, is appropriately adapted to reflect the structural changes of the polymer molecules and then used to identify possible relationships between molecular structure and viscoplastic behavior. The simple theory for flexible polymers is modified to include the possibility of complex formation by association between neighboring polymer molecules. We conclude that, although the model is sensitive to the average molar mass of the polymer, additional and more extensive high-shear-rate data are required to explore fully the validity of the Rouse description. However, the scaling of the viscosity by the addition of an increased friction factor provides a reasonable description of the short-range motions observed. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie302313a

Solvent effects on cure in a 2K polyurethane — mechanical and dielectric studies / Stephen Monaghan in Industrial & engineering chemistry research, Vol. 51 N° 34 (Août 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 34 (Août 2012) . - pp. 11038-11044 Titre : Solvent effects on cure in a 2K polyurethane — mechanical and dielectric studies Type de document : texte imprimé Auteurs : Stephen Monaghan, Auteur ; Richard A. Pethrick, Auteur Année de publication : 2012 Article en page(s) : pp. 11038-11044 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Solvent  effect Résumé : The effect of change in solvent type on the processes involved in film formation of a 2K polyurethane are investigated using dynamic mechanical thermal analysis [DMTA] and dielectric relaxation [DR] measurements. The film formation and cure reactions for a polyol reacting with an isocyanate for solutions in ethyl acetate, tolene, xylene, and n-butyl acetate solutions and their mixtures are reported. Mechnical studies are used to observe the various stages of film formation and cure using a paper substrate. The fluid initially wets the substrate and film formation accompanies solvent evaporation. The rate of these initial processes correlates well with the vapor pressure of the solvent. The rate of cure of the films however is influenced by the polarity of the solvent system. Analysis of the broad band dielectric relaxation data yields conductivity data, which can be modeled to give kinetic data on the cure process. The rate of cure of this 2K system demonstrates sensitivity to the solvent composition used. The rate constant derived from conductivity data parallel those derived previously from FTIR studies. DMTA and DR measurements indicate that as cure proceeds, the glass transition temperature—Tg, increases. Differences are observed in the ambient temperature-cured films, which reflect retained solvent plasticization. of the matrix. Post cure aids release of trapped solvent and the final physical properties are essentially independent of the solvent used in the cure process. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=26299426 [article] Solvent effects on cure in a 2K polyurethane — mechanical and dielectric studies [texte imprimé] / Stephen Monaghan, Auteur ; Richard A. Pethrick, Auteur . - 2012 . - pp. 11038-11044. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 34 (Août 2012) . - pp. 11038-11044 Mots-clés : Solvent  effect Résumé : The effect of change in solvent type on the processes involved in film formation of a 2K polyurethane are investigated using dynamic mechanical thermal analysis [DMTA] and dielectric relaxation [DR] measurements. The film formation and cure reactions for a polyol reacting with an isocyanate for solutions in ethyl acetate, tolene, xylene, and n-butyl acetate solutions and their mixtures are reported. Mechnical studies are used to observe the various stages of film formation and cure using a paper substrate. The fluid initially wets the substrate and film formation accompanies solvent evaporation. The rate of these initial processes correlates well with the vapor pressure of the solvent. The rate of cure of the films however is influenced by the polarity of the solvent system. Analysis of the broad band dielectric relaxation data yields conductivity data, which can be modeled to give kinetic data on the cure process. The rate of cure of this 2K system demonstrates sensitivity to the solvent composition used. The rate constant derived from conductivity data parallel those derived previously from FTIR studies. DMTA and DR measurements indicate that as cure proceeds, the glass transition temperature—Tg, increases. Differences are observed in the ambient temperature-cured films, which reflect retained solvent plasticization. of the matrix. Post cure aids release of trapped solvent and the final physical properties are essentially independent of the solvent used in the cure process. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=26299426