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Two-component waterborne polyurethanes : The rheology of mixing / H. Bui in EUROPEAN COATINGS JOURNAL (ECJ), N° 5/97 (05/1997)

[article]  inEUROPEAN COATINGS JOURNAL (ECJ) > N° 5/97 (05/1997) . - p. 476-481 Titre : Two-component waterborne polyurethanes : The rheology of mixing Type de document : texte imprimé Auteurs : H. Bui, Auteur ; M. Dvorchak, Auteur ; K. Hudson, Auteur ; J. Hunter, Auteur Année de publication : 1997 Article en page(s) : p. 476-481 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Bois -- Revêtements Composés organiques volatils Formulation (Génie chimique) Mélanges (chimie) Polyisocyanates Polyols Polyuréthanes Revêtements bi-composant:Peinture bi-composant Revêtements en phase aqueuse:Peinture en phase aqueuse Rhéologie Index. décimale : 667.9 Revêtements et enduits Résumé : Two-component waterborne polyurethane systems for wood can be formulated with ultralow Volatile Organic Compounds (VOC) and Volatile Hazardous Air Pollutants (VHAPs). Due to the high surface tension of these systems, and the high viscosity of polyisocyanates relative to the polyol dispersion, problems still remain with mixing in industrial applications. The high viscosity causes gel formation in the in-line mixing apparatus, and the high surface tension and air entrapment cause microfoam in the final film. Therefore, the rheology of dynamic and static mixing of the system was studied in detail. The results show that the critical parameters for controlling the properties of the coatings are 1) viscosity of polyisocyanates and 2) particle size of the mixture of polyol and polyisocyanate under both low and high shear flow fields. With this knowledge, the spray equipment and formulation were modified for wood applications to give better spraying with no gel formation and reduced microfoam. Note de contenu : - Chemistry of two-component waterborne polyurethanes - Problems with two-component waterborne polyurethane coatings - Materials - Experimental - Formulation for wood coatings applications - Morphology of polyisocyanate and polyol latex in water - Batch mixing - Dynamic Mixing - Modification of spray equipment - Comparisons of mixing methods Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=11403 [article]

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Oligourethane diol/melamine high solids / M. Yaseen in EUROPEAN COATINGS JOURNAL (ECJ), N° 5/97 (05/1997)

[article]  inEUROPEAN COATINGS JOURNAL (ECJ) > N° 5/97 (05/1997) . - p. 482-486 Titre : Oligourethane diol/melamine high solids : Baking schedules in terms of cure window Type de document : texte imprimé Auteurs : M. Yaseen, Auteur ; Syed Haseebuddin, Auteur ; K. V. S. N. Raju, Auteur Année de publication : 1997 Article en page(s) : p. 482-486 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Haut extrait sec Mélamine La mélamine, de nom chimique 1,3,5-triazine-2,4,6-triamine, est parfois dénommée cyanuramide ou cyanurotriamine. Sa formule brute est C3H6N6. Les "résines mélamine-formaldéhyde" ou "mélamine-formol" (sigle MF) sont appelées "mélamine" dans le langage courant. Elles font partie de la famille des aminoplastes qui regroupe des résines thermodurcissables aminées, issues d'un comonomère tel l'urée ou la mélamine, parfois le thiocarbamide, le cyanamide hydrogène ou le dicyandiamide ; le second comonomère étant le formaldéhyde. Oligomères Polyuréthanes Réticulation (polymérisation) Revêtements organiques Index. décimale : 667.9 Revêtements et enduits Résumé : The cure behaviour of oligourethane diols crosslinked with melamine formaldehyde resin is influenced by the amount of the crosslinker used in the formulation and by the bake temperature. In the course of baking major part of the cross-linker is consumed in trans-etherification reaction and a part of it undergoes selfcondensation. The aromatic nature of TDI imparts rigidity while aliphatic IPDI results in flexibility of the backbone chain of oligomer. In the case of formulations containing 30% cross-linker baked at 140°C for 20 min, a major part of the reaction is completed which indicates the ideal condition for crosslinking. The findings indicate that the knowledge about the cure schedules is essential to control the poor durability, resistance to solvents, mar or scratch of underbake coatings as well as lack of flow and levelling, brush strokes, roller striations, orange peel, wrinkling and yellowing of overbake coatings. The profile of cure schedules has been determined in the form of Cure Window which measures the extent of reaction in terms of crosslink density as function of bake temperature. The width of the cure window has direct application to paint cure uniformity. The lower and upper range of temperatures for baking the coatings has been illustrated in terms of Nominal and True Cure Windows. Note de contenu : - Cure Window - Experimental : Oligourethane diol - Melamine crosslinker - Coating formulation - Preparation of free film of cured resin - Procedure for the determination of crosslinking density of cured resin - Results : Construction of cure window - Nominal & true cure window Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=11404 [article]

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Colloid chemistry, part II : Film forming dispersions / Vladimir V. Verkholantsev in EUROPEAN COATINGS JOURNAL (ECJ), N° 5/97 (05/1997)

[article]  inEUROPEAN COATINGS JOURNAL (ECJ) > N° 5/97 (05/1997) . - p. 488-492 Titre : Colloid chemistry, part II : Film forming dispersions Type de document : texte imprimé Auteurs : Vladimir V. Verkholantsev, Auteur Année de publication : 1997 Article en page(s) : p. 488-492 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Colloides Dispersions et suspensions Liants Revêtements en phase aqueuse:Peinture en phase aqueuse Index. décimale : 667.9 Revêtements et enduits Note de contenu : - Classification : Preparation method - Lyophilicity of the dispersed phase - Stabilization factors - Descriptions and general features: - Lyophilic colloids ( LCs)- Microemulsions and solubilizates - Self-emulsifiables resins - Organosoles - Hydrosoles, latexes, emulsions Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=11405 [article]

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Partially fluorinated automotive coatings / William Graham in EUROPEAN COATINGS JOURNAL (ECJ), N° 5/97 (05/1997)

[article]  inEUROPEAN COATINGS JOURNAL (ECJ) > N° 5/97 (05/1997) . - p. 494-496 Titre : Partially fluorinated automotive coatings Type de document : texte imprimé Auteurs : William Graham, Auteur Année de publication : 1997 Article en page(s) : p. 494-496 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Automobiles -- Industrie et Commerce Chimie des surfaces Fluoration Fluoropolymères Liants Polyacrylates Polyisocyanates Revêtements Tension superficielle Vernis Index. décimale : 667.9 Revêtements et enduits Résumé : Customer expectations, environmental concerns, and increasing global competition have combined to bring about a great deal of change in automotive clearcoat technology. New product improvement expectations are continuously being added to the already high performance standards that have been achieved in the recent past. One of our areas of focus has been the development of new technology which can impart improved graffiti resistance and cleanability to current automotive and truck clearcoats. The surface properties of a new isocyanate cured clearcoat have been dramatically enhanced with this new technology that effectively places fluorinated components at the polymer/air interface of an acrylic coating. This has been achieved through the use of a novel free radical solution polymerization process which incorporates small amounts of a long chain perfluoroalkyl containing methacrylate monomer into the polymer backbone. Due to stratification of the fluorine-containing portion, a Teflon-like surface is achieved without compromising other desirable properties of the clearcoat. Surface energies of 12-14 dynes/cm have been obtained at very low levels of fluorine. Surface energy considerations have also required the development of a lightly fluorinated isocyanate. The development and analysis of this new technology will be discussed. Note de contenu : - Synthesis of acrylic resin systems - Surface tension of acrylated resins - Fluorinated isocyanate development Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=11406 [article]

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