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Star oligomers with different reactivity in low VOC polyurethane coatings : part II / J. Huybrechts in SURFACE COATINGS INTERNATIONAL, Vol. 81, N° 4 (04/1998)
[article]
Titre : Star oligomers with different reactivity in low VOC polyurethane coatings : part II Type de document : texte imprimé Auteurs : J. Huybrechts, Auteur ; K. Dusek, Auteur Année de publication : 1998 Article en page(s) : p. 172-177 Note générale : Bibliogr. Langues : Anglais (eng) Tags : 'Peinture deux constituants' Liant Polyuréthane Oligomère 'Polymère étoile' 'Composé organique volatil' réticulé' Réticulation Index. décimale : 667.9 Revêtements et enduits Résumé :
In this paper the effects of the reactivity of hydroxyl functional oligomers with a polyisocyanate crosslinking agent have been demonstrated by comparing the potlife/hardness of a 3.5 VOC two-component polyurethane clear coat based on a low TG, high reactive against a high TG, low reactive oligomer.
The reaction rate of two polymers forming a crosslinked network becomes diffusion controlled when, during the reaction, the increasing TG comes close to the reaction temperature.4 If this reaction takes place in the presence of a solvent which evaporates during film formation and crosslinking, the speed of evaporation will affect both the reaction rate and the film TG. The results of this study have shown that the reactivity determines the potlife whilst the TG controls the hardness. The reactivity of blends of such oligomers against pure oligomers is different as can be calculated using the theory of branching processes and as shown from practical measurements. Blends of oligomers or a pure oligomer with up to 75% of the properties of the high TG, low reactive oligomer do show a hardness close to the properties of the low TG, high reactive oligomer which further proves that the chemical reactivity controls the overall drying performance. A fast chemical reactivity shortens the potlife with a risk of solvent entrapment near to and at the gel point which results in low hardness.Note de contenu : - THEORETICAL BACKGROUND : Star with groups of different reactivity - Network build-up and gelation - Kinetics - Mixture of more and less reactive stard - Gelation and network formation - Kinetics Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=16528
in SURFACE COATINGS INTERNATIONAL > Vol. 81, N° 4 (04/1998) . - p. 172-177[article]Réservation
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[article]
Titre : The star performer : Star-shaped molecule produces pigment concentrates with very low VOC content Type de document : texte imprimé Auteurs : Sandra Bauer, Auteur ; Frank Kleinsteinberg, Auteur ; Ellen Reuter, Auteur ; Patrick Glöckner, Auteur Année de publication : 2010 Article en page(s) : p. 26-31 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Agents dispersants (chimie)
Formulation (Génie chimique)
Pigments
Revêtements -- Additifs:Peinture -- Additifs
ViscosimétrieTags : Peinture Additif 'Molécule en étoile' 'Agent mouillant' 'Agents dispersants' 'Pigments concentrés' 'Réduction des COV' Index. décimale : 667.9 Revêtements et enduits Résumé : Three wetting and dispersing additives were compared for their ability to produce high solids pigment concentrates. In most formulations, na new star-shaped dispersant provided exceptional viscosity reduction, thus allowing VOC levels to be reduced in mixing paints, concentrates and direct grinds. It is also shown that binder-free concentrates are not always more expensive than those using a grinding resin. En ligne : https://drive.google.com/file/d/15EYaedphF9PmH-9uPN6LkNruWt9rNk32/view?usp=drive [...] Format de la ressource électronique : Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=9749
in EUROPEAN COATINGS JOURNAL (ECJ) > N° 05/2010 (05/2010) . - p. 26-31[article]Réservation
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