Direct observation of freeze-thaw instability of latex coatings via high pressure freezing and cryogenic SEM / Cheng-Le Zhao in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH, Vol. 3, N° 2 (04/2006)  

[article]  inJOURNAL OF COATINGS TECHNOLOGY AND RESEARCH > Vol. 3, N° 2 (04/2006) . - p. 109-115 Titre : Direct observation of freeze-thaw instability of latex coatings via high pressure freezing and cryogenic SEM Type de document : texte imprimé Auteurs : Cheng-Le Zhao, Auteur ; L. E. Scriven, Auteur ; H. Ted Davis, Auteur ; Haiyan Ge, Auteur ; Alan Smith, Auteur ; Shane J. Stafslien, Auteur Année de publication : 2006 Article en page(s) : p. 109-115 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Colloides Composés organiques volatils Copolymères greffés Floculation Latex Microscopie électronique à balayage Morphologie (matériaux) Oxyde d'éthylène L'oxyde d'éthylène, ou 1,2-époxyéthane, oxyde de diméthylène, oxacyclopropane, ou encore oxirane est un composé organique, le plus simple de la classe des époxydes. Il est important pour l'industrie chimique, entre autres dans la production d'éthylène glycol, ainsi que dans les industries pharmaceutique et agroalimentaire. Polyacryliques Polyméthacrylate de butyle Revêtements en bâtiment:Peinture en bâtiment Revêtements en phase aqueuse:Peinture en phase aqueuse Stabilité thermique Index. décimale : 667.9 Revêtements et enduits Résumé : Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively. There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized. High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing, and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually preserves suspension stability during freezing. DOI : 10.1007/s11998-006-0013-6 En ligne : https://link.springer.com/content/pdf/10.1007%2Fs11998-006-0013-6.pdf Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=3701 [article]

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MFFT of copolymer dispersions / Manfred Schwartz in EUROPEAN COATINGS JOURNAL (ECJ), N° 12/00 (12/2000)

[article]  inEUROPEAN COATINGS JOURNAL (ECJ) > N° 12/00 (12/2000) . - p. 34-41 Titre : MFFT of copolymer dispersions Type de document : texte imprimé Auteurs : Manfred Schwartz, Auteur ; Cheng-Le Zhao, Auteur Année de publication : 2000 Article en page(s) : p. 34-41 Langues : Anglais (eng) Index. décimale : 667.9 Revêtements et enduits Résumé : Emulsion based paints can be formulated with a variety of chemically different polymer dispersions. These binders are mainly based on acrylic or vinyl ester copolymers. The present publication treats comparative experiments of acrylic copolymers having different minimum film forming temperatures (MFFT). For masonry, as in many applications, the principle question is, which is the right performance profile for a copolymer dispersion based on acrylic and styrene monomers to achieve a long lasting paint? Further, the market is looking for binders which permit the formulation of solvent-free architectural coatings. This requirement can be achieved by using a binder having suitable MFFT. The MFFT of such a binder should be below 5°C. We want to discuss similarities and differences between acrylic/styrene emulsions having different MFFTs. Note de contenu : - Results of tests made with polymer films - Paint formulations and pigments used - Brightness as function of the binder and TiO2- type - Colour changes in artificial weathering - Chalking tendency increase in the "Xeno-1200-test" - Dirt accumulation on outdoor coatings protects the binder against degration - Outdoor exposure shows influence of the binder - Result at a glance Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=11063 [article]

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