Effects of latex and thickener polarities on rheology and phase stability of latex-HEUR mixtures / Travis B. Smith in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH, Vol. 20, N° 4 (07/2023)  

[article]  inJOURNAL OF COATINGS TECHNOLOGY AND RESEARCH > Vol. 20, N° 4 (07/2023) . - p. 1311-1324 Titre : Effects of latex and thickener polarities on rheology and phase stability of latex-HEUR mixtures Type de document : texte imprimé Auteurs : Travis B. Smith, Auteur ; David Chisholm, Auteur ; Abby Cheng, Auteur ; Juan Ortiz Salazar, Auteur ; Lia Roccucci, Auteur ; Bailey Morales, Auteur ; Gary Dombrowski, Auteur ; John J. Rabasco, Auteur ; Patrick Hartnett, Auteur ; Ray Fernando, Auteur Année de publication : 2023 Article en page(s) : p. 1311-1324 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Cisaillement (mécanique) Epaississants Epaississement Floculation Latex Polyuréthane éthoxylé modifié de façon hydrophobe Revêtements en phase aqueuse:Peinture en phase aqueuse Rhéologie Synérèse En chimie, la synérèse définit la séparation d'un liquide de son gel. Index. décimale : 667.9 Revêtements et enduits Résumé : In this study, hydrophobically modified, ethoxylate urethanes (HEURs) and latexes of well-defined structure and composition were used to examine the rheology and phase behavior of HEUR–latex mixtures. The mixtures comprised one of four HEURs that were synthesized with varying molecular weight polyethylene glycols (PEG 35 K, 20 K, 12 K, and 8 K) and end-capped with octadecyl hydrophobes, as well as one of two latexes (butyl acrylate/styrene [BA-Sty] and butyl acrylate/methyl methacrylate [BA-MMA]) that each contained a small amount of methacrylic acid. The two experimental latexes represent compositions commonly used in commercial paint formulations. The polarity of the HEURs decreases as the PEG molecular weight decreases and the surface of the styrene containing latex is less polar than that containing methyl methacrylate. In all HEUR–latex mixtures, the latex polymer volume fraction was maintained constant at 0.25 which provides a dispersed component spatial crowdedness that represents a fully formulated paint. All latex–HEUR mixtures were stable at very low (i.e., below 0.10% by weight) HEUR levels. At critical concentrations dependent on the polarity of thickener and latex, flocculation was accompanied by syneresis for latex-thickener mixtures prepared with all HEURs except the one with the longest PEG spacer. Further increase of HEUR levels revealed another critical concentration above which the mixtures were stable. Effects of the latex polarity diminished for the mixtures prepared with more hydrophobic HEURs. Note de contenu : - HEUR C18-EO795 and latex mixtures - HEUR C18-EO455 and latex mixtures - Table 1 : Compositions and molecular weights (determined by GPC) of model HEURs - Table 2 : Properties of model latexes - Table 3 : Compositions of representative latex–HEUR mixtures - Table 4 : Visual assessment of stability of latex–HEUR samples after 6–8 days of equilibration - Table 5 : Number of HEUR molecules available per BA-Sty latex particle - Table 6 : Latex surface area (nm2) claimed by a HEUR hydrophobe, assuming one of the hydrophobes from every HEUR molecule is adsorbe DOI : https://doi.org/10.1007/s11998-022-00746-3 En ligne : https://link.springer.com/content/pdf/10.1007/s11998-022-00746-3.pdf?pdf=button% [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=39718 [article]

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Syneresis and rheology mechanisms of a latex-HEUR associative thickener system / Franceska A. Santos in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH, Vol. 14, N° 1 (01/2017)  

[article]  inJOURNAL OF COATINGS TECHNOLOGY AND RESEARCH > Vol. 14, N° 1 (01/2017) . - p. 57-67 Titre : Syneresis and rheology mechanisms of a latex-HEUR associative thickener system Type de document : texte imprimé Auteurs : Franceska A. Santos, Auteur ; Tyler J. Bell, Auteur ; Alexandra R. Stevenson, Auteur ; Dana J. Christensen, Auteur ; Michaela R. Pfau, Auteur ; Brendan Q. Nghiem, Auteur ; Christopher R. Kasprzak, Auteur ; Travis B. Smith, Auteur ; Raymond H. Fernando, Auteur Année de publication : 2017 Article en page(s) : p. 57-67 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Adsorption Epaississants Floculation Latex Polyuréthane éthoxylé modifié de façon hydrophobe Rhéologie Synérèse En chimie, la synérèse définit la séparation d'un liquide de son gel. Index. décimale : 667.9 Revêtements et enduits Résumé : This study focuses on the phase behavior, rheology, and interactions of polymer latex particles and a hydrophobically modified ethoxylated urethane (HEUR) associative thickener in water. At constant 0.25 latex particle volume fraction, increasing HEUR caused stable, followed by phase separated (syneresis), and stable mixtures as HEUR concentration increased from 0% to 2.0% (by weight) in the latex-thickener aqueous mixture. The mixtures that underwent syneresis were flocculated. The relationship between the flocculation behavior and the composition of the latex-HEUR mixtures is consistent with previous work reported by other investigators. However, detailed rheological data on systems like these that have undergone syneresis have not been reported. This paper presents detailed viscosity vs shear rate data and correlates viscosity trends with the both flocculation and syneresis behavior. The stable latex-HEUR mixtures at low HEUR levels show Newtonian or shear-thinning viscosity with well-defined low-shear Newtonian plateaus. As HEUR level is increased to levels at which syneresis is observed, erratic rheological profiles with shear thinning as well as thickening are observed. This type of shear thickening has been attributed to bridging flocculation by other investigators. When HEUR level is further increased to levels at which no syneresis is observed, low-shear Newtonian plateaus re-appeared, albeit at higher viscosities. Detailed analysis of syneresis and shear-thickening behavior of a latex-HEUR mixture containing 0.5% (by weight) HEUR showed two shear-thickening regions, one between 0.1 and 0.5 s−1 shear rate range and another between 30 and 100 s−1 shear rate range. Molecular weight distribution (MWD) of the HEUR thickener indicates that the two shear-thickening regions are related to the bi-modal nature of the thickener’s MWD. Note de contenu : - Thickening of aqueous phase - Adsorption - Bridging flocculation of dispersed particles - Depletion flocculation of dipersed particles - Effect of shear rate on thickening mechanisms DOI : 10.1007/s11998-016-9829-x En ligne : https://link.springer.com/content/pdf/10.1007%2Fs11998-016-9829-x.pdf Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=27789 [article]

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