[article]
| Titre : |
Non-isocyanate coatings with fast return to service and excellent appearance for industrial flooring application |
| Type de document : |
texte imprimé |
| Année de publication : |
2022 |
| Article en page(s) : |
p. 448-449 |
| Langues : |
Anglais (eng) |
| Catégories : |
Durée de vie en pot
Formulation (Génie chimique)
Michael, Addition deL'addition de Michael ou réaction de Michael est une réaction qui permet la création de liaisons carbone-carbone, voire de liaisons carbone-soufre. Il s'agit de l'addition nucléophile d'un carbanion sur un composé carbonylé α,β insaturé (aldéhyde, cétone et même ester α,β insaturé, des nitriles et des amides α,β insaturés pouvant aussi être utilisés). Elle appartient à la famille des additions nucléophiles conjuguées.
Cette réaction doit son nom au chimiste américain Arthur Michael.
Revêtements de sols industriels
Revêtements organiques
Revêtements sans isocyanates
Rhéologie
|
| Index. décimale : |
667.9 Revêtements et enduits |
| Résumé : |
Floor coatings are of great importance in the industrial, commercial, and architectural markets because they provide protection to the substrate and aesthetics to the environment. Concrete floors are the preferred substrate due to hardness, durability, relative low cost, and ease of installation. However, concrete floors lack chemical resistance and flexibility to achieve different degrees of finish (high gloss, colors, special effects, etc.). A wide range of polymer technologies are used as protective coatings ranging from acrylic emulsions or thermoplastic acrylics to high-performance two-component (2K) systems such as epoxies, polyaspartics, and polyurethanes (PUs).
The application properties of these coatings have a very big impact on the total installed cost. In this cost, end-users will also consider the opportunity cost of downtime. Therefore, systems that enable fast return to service are preferree, which generally requires a thermoplastic material or high reactivity. Technologies like MMA and poly-aspartic exhibit high reactivity, which in turn requires a high proficiency of the applicators. During the application of floor coatings on large sections, such as warehouses or airplane hangars, a long open time is needed to avoid lapping marks. Such marks result when the coating applied on the first section starts curing so fast that the adjacent second section (generally overlapping 2.5-7.5 cm) does not blend-in with the first layer. Another problem arises from the reaction of the chemicals as soon as they are mixed, which limits the time by which these can be applied (termed the pot-life). PA MMA, 2K PU tipically increase in viscosity or form a gel, while epoxy systems tend to lose gloss. With epoxies this can results in a gradient appearance from one end to another end of the coated surface. End of pot-life typically requires the coating to be disposed of as there is no way to reverse the reaction.
A novel technology called ACURE has proven the possibility of using Michael addition (MA) chemistry by using a blocked catalyst. ACURE relies on the formation of carobn-carbon bonds when an acidic proton is abstracted from a malonate groupe by a strong base. The resulting carbanion reacts with the partially positive carbon in the π bond of an acrylate group. The catalyst is designed to de-block via evaporation, generating ethanol and carbon dioxide after the coating has been applied, and allowing the de-blocked strong base to initiate the fast polymerisation reaction. Nevertheless, if the activated coating remains in a closed container, the system reaches equilibrium and the deblocking of the catalyst is inhibited, thus the activated coating will remain in the liquid state for an extended period. |
| Note de contenu : |
- Fig. 1 : Michael addition chemistry applied in polymers
- Fig. 2 : Lapping time evaluated at 20 minutes (60 % R.H. and 23°C)
- Fig. 3 : Technology comparison |
| En ligne : |
https://www.paint.org/wp-content/uploads/2022/02/Non-Isocyanate-Coatings-Industr [...] |
| Format de la ressource électronique : |
Pdf |
| Permalink : |
https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=38675 |
in SURFACE COATINGS INTERNATIONAL > Vol. 105.6 (11-12/2022) . - p. 448-449
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Non-isocyanate coatings with fast return to service and excellent appearance for industrial flooring application in SURFACE COATINGS INTERNATIONAL, Vol. 105.6 (11-12/2022)
