Crosslinking vs. interdiffusion rates in melamine-formaldehyde cured latex coatings : a model for waterborne automotive basecoat / Mitchell A. Winnik in JOURNAL OF COATINGS TECHNOLOGY (JCT), Vol. 71, N° 892 (05/1999)

[article]  inJOURNAL OF COATINGS TECHNOLOGY (JCT) > Vol. 71, N° 892 (05/1999) . - p. 47-60 Titre : Crosslinking vs. interdiffusion rates in melamine-formaldehyde cured latex coatings : a model for waterborne automotive basecoat Type de document : texte imprimé Auteurs : Mitchell A. Winnik, Auteur ; Patrick Pinenq, Auteur ; Christian Krüger, Auteur ; Jianxin Zhang, Auteur ; Phillip V. Yaneff, Auteur Année de publication : 1999 Article en page(s) : p. 47-60 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Automobiles -- Revêtements:Automobiles -- Peinture Copolymère mélamine-formaldéhyde Polyacrylates Réticulation (polymérisation) Revêtements en phase aqueuse:Peinture en phase aqueuse Index. décimale : 667.9 Revêtements et enduits Résumé : Designing optimal formulations for automotive waterborne basecoats can be fairly complex, often requiring knowledge of events that occur at the molecular level. The ultimate performatce of the coating can depend upon the success with which this knowledge is applied. We examine a system in which an aqueous dispersion of an acrylic latex with -OH functionality reacts with a melamine derivative when heated. We use fluorescence-labeling and energy transfer measurements to obtain information on the relative rates of crosslinking and interparticle polymer diffusion in these films. We show that temperature and particle morphology play an important role in the development of film properties. Finally, these energy transfer experiments provide information on the location of the melamine-formaldehyde resin in the dry film before the onset of crosslinking. This system can serve as a model for waterborne basecoat development in many automotive applications. Note de contenu : - EXPERIMENTAL : Materials - Latex characterization - Film formation, annealing, and fluorescence measurements - FLUORESCENCE DATA AND DATA ANALYSIS - RESULTS AND DISCUSSION : Latex preparation and characterization - Where is the melamine located ? - Crosslinking, gel content, and swell ratio - Polymer interdiffusion - Core-Shell latex films Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=17853 [article]

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Polymer diffusion and mechanical properties of films prepared from crosslinked latex particles / Patrick Pinenq in JOURNAL OF COATINGS TECHNOLOGY (JCT), Vol. 72, N° 903 (04/2000)

[article]  inJOURNAL OF COATINGS TECHNOLOGY (JCT) > Vol. 72, N° 903 (04/2000) . - p. 45-61 Titre : Polymer diffusion and mechanical properties of films prepared from crosslinked latex particles Type de document : texte imprimé Auteurs : Patrick Pinenq, Auteur ; Mitchell A. Winnik, Auteur ; Benoit Ernst, Auteur ; Didier Juhué, Auteur Année de publication : 2000 Article en page(s) : p. 45-61 Note générale : Bibliogr. Langues : Américain (ame) Tags : Matériau  revêtement  Peinture  eau  émulsion  Formation  film  Latex  Réticulation  Polymère  Diffusion  Transfert  énergie  Propriété  mécanique  Feuil  Résistance  traction  Etude  expérimentale Index. décimale : 667.9 Revêtements et enduits Résumé : We have carried out energy transfer (ET) measurements to follow polymer diffusion, as well as oscillatory dynamic mechanical measurements and tensile measurements, on films prepared from structured and unstructured latex particles. All the particles had the same global chemical composition. The base polymer was a copolymer of butyl methacrylate and butyl acrylate with a glass transition temperature (Tg) of 20°C. Structure was introduced in the form of a low level (1 mol%) of crosslinking using seeded semi-continuous emulsion polymerization to control the locus of the crosslinking agent in the particles. Most of the samples were also labeled with donor or acceptor dyes so that ET experiments could be carried out. In this way we could monitor the extent of interdiffusion that occurred in each of the latex films as a function of annealing history. These ET experiments proved to be particularly useful for determining particle morphology for core-crosslinked particles in which only the core was labeled. The linear dynamic mechanical measurements showed that G' and G were sensitive to the particle morphology, with particular sensitivity exhibited by the elastic modulus G'. The tensile properties were less sensitive to particle morphology. Films for tensile experiments were substantially thicker (0.8 mm) than those commonly used for ET studies of polymer diffusion in latex films. Film thickness has no effect on the polymer diffusion rate, but the films for tensile testing were subjected to prolonged drying at 39°C. Under these conditions, sufficient polymer interdiffusion occurs during film formation for the films to acquire substantial strength and toughness, with elongation at break much larger than 100%. Some differences due to morphology are apparent. Films formed from fully crosslinked latex and from core-crosslinked latex with a large core fraction (50 vol%) have somewhat larger tensile strengths, yield strengths, and toughness than those formed from uncrosslinked latex or latex with a small (12 vol%) crosslinked core. These differences become less pronounced when the samples are annealed for long periods of time (100+ hr) at 80°C. Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=5816 [article]

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