| Titre : |
Convective flow and defects |
| Type de document : |
texte imprimé |
| Auteurs : |
Clifford K. Schoff, Auteur |
| Année de publication : |
2018 |
| Article en page(s) : |
p. 76 |
| Langues : |
Américain (ame) |
| Catégories : |
Revêtement -- Séchage:Peinture -- Séchage
Revêtements -- Défauts:Peinture -- Défauts
|
| Index. décimale : |
667.9 Revêtements et enduits |
| Résumé : |
After a coating is applied, there is a period when the film is still liquid. Evaporation of solvent or water cools the surface and entry into an oven heats the surface. In either case, a combination of density and surface tension differences can cause convective flow within the film as shown in Figure 1. Material moves from the coating-substrate interface, rises to the surface, then drops back down. The motion continues until the coating has dried or cured enough to raise the viscosity to a level that stops flow. In multi-pigment systems, one of the pigments rising with the flow may be trapped at the surface producing the defects called flooding and floating. If that pigment completely covers the surface or has become the major component of the pigment mix at the surface, the result is a darker or lighter shade of uniform color. We usually call this flooding. Rubbing the wet paint with a finger (known as rub-up) will show that the surface color is different from the interior of the layer. Partial coverage by one pigment resulting in ugly streaks or mottled regions is called floating, although both defects sometimes are labeled as floating since, in both cases, pigment is floating to the surface. Flooding and floating both produce unacceptable color effects. |
| Note de contenu : |
- Fig. 1 : Diagram of convective flow showing the up and down pattern of motion
- Fig. 2 : Example of a network of Bénard cells
- Fig. 3 : Bénard cells in a white can coating |
| En ligne : |
https://drive.google.com/file/d/1GOTN5P9DIU2ogYQEXOQxaf0J6b1yBfZA/view?usp=drive [...] |
| Format de la ressource électronique : |
Pdf |
| Permalink : |
https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=30628 |
in COATINGS TECH > Vol. 15, N° 3 (03/2018) . - p. 76
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Convective flow and defects in COATINGS TECH, Vol. 15, N° 3 (03/2018)
