Scratch- and mar-resistant refinish two-pack clear coats - linear versus branched acrylics / J. Huybrechts in SURFACE COATINGS INTERNATIONAL. PART B : COATINGS TRANSACTIONS, Vol. 89, B4 (12/2006)  

[article]  inSURFACE COATINGS INTERNATIONAL. PART B : COATINGS TRANSACTIONS > Vol. 89, B4 (12/2006) . - p. 275-283 Titre : Scratch- and mar-resistant refinish two-pack clear coats - linear versus branched acrylics Type de document : texte imprimé Auteurs : J. Huybrechts, Auteur ; A. Vaes, Auteur ; K. Dusek, Auteur ; M. Duskova-Smrckova, Auteur ; R. Barsotti, Auteur Année de publication : 2006 Article en page(s) : p. 275-283 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Automobiles -- Vernis Copolymères Copolymères greffés Polyacryliques Polymères ramifiés Polyols Résistance à l'abrasion Résistance à l'usure Vernis bi-composant Index. décimale : 667.9 Revêtements et enduits Résumé : The new generation clear coats introduced in the automotive industry have improved scratch and mar resistance. It is believed that those properties are related to the introduction of new binder technologies leading to higher film cross-link densities. This was relatively easy to accomplish in the automotive industry because baking temperatures are well above the glass-transition temperature (Tg) of the final clear coat film. In car repair coatings, the cross-linking takes place under conditions where the intermediate and/or final film Tg values are above the curing temperature. Such formulations result in vitrification during the drying process, a transition during which chemical cure and solvent release are slowed down substantially. The chemical cure can be improved through more reactive and/or higher functional binders, but this shifts the gel point to shorter times in the drying cycle which may lead to more solvent entrapment, resulting in low film hardnesses and paint defects. This paper describes the overall properties of 2K-refinish clear coats based on linear versus branched, random and graft acrylic polyols. The authors will try to correlate overall properties with theoretical predictions and practical results. Note de contenu : - EXPERIMENTAL : Binders, cross-linkers and clear coat formulations - Physical measurements on clear coats - THEORETICAL BACKGROUND - Table 1 : Physical properties of linear and branched graft acrylics - Table 2 : Film Tg values, swell ratios and gel fractions at different catalyst levels and baking cycles, measurement after 30 days of ageing at room temperature - Table 3 : Gel time for a 55% solution of different acrylics activated with HDI trimer at 500 ppm DBTDL - Table 4 : Theoretical calculations of ve, WSov Wge~ and NCO conversion at the gel point for reaction of the BACR H and LACR H at different OH/NCO ratios and practical measurements Tg, Mn and Mw for film cross-linked at 140~ (I = insoluble) - Table 5 : Property balance of different clear coats based on structured acrylics versus a commercial standard applied over a dark blue metallic basecoat at specified baking conditions DOI : 10.1007/BF02765579 En ligne : https://link.springer.com/content/pdf/10.1007/BF02765579.pdf Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=5268 [article]

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