| Titre : |
Reduction of air bubbles in spray-applied coatings |
| Type de document : |
texte imprimé |
| Auteurs : |
Matthew S. Gebhard, Auteur ; L. E. Scriven, Auteur |
| Année de publication : |
1994 |
| Article en page(s) : |
p. 27-39 |
| Note générale : |
Bibliogr. |
| Langues : |
Américain (ame) |
| Tags : |
Peinturage Pulvérisation 'Bulle air' 'Peinture eau' Défaut 'Etude expérimentale' 'Photographie rapide' 'Technique vidéo' |
| Index. décimale : |
667.9 Revêtements et enduits |
| Résumé : |
Microfoam (i.e., tiny (10 μm) air bubbles) in spray-applied coatings is a frequently encountered problem which may be aggravated in water-based coatings. This paper describes recent work to understand the dynamics of the microfoam formation and dissipation process. The data indicate that the majority of microfoam does not form by the splashing of atomized drops on the building liquid film. In fact, the atomized drops arrive at the substrate with numerous air bubbles, and poor atomization is observed to be a key to the problem. It is found that air bubbles dissipate through a dissolution mechanism and not the generally accepted rise and rupture mechanism. The dissolution is driven by surface tension and is mediated by diffusion through the liquid. The experimental data are found to agree with the Epstein and Plesset model, with lower diffusion coefficients, lower air solubility, and lower surface tension reducing the dissolution rate. This study has led to a novel solution to the problem and involves using carbon dioxide (CO2) as the driving gas instead of air. It is found that this leads to a significant reduction in entrapped air in conventional, high volume low pressure (HVLP), and air-assisted airless spray techniques. This approach is found to work because of the much higher solubility of CO2 in water versus air in water. |
| Note de contenu : |
- EXPERIMENTAL : High-speed video microscopy - High-speed photography - Dissolution measurements - Determination of diffusion coefficients - Spray applications using CO2 and air
- RESULTS AND ANALYSIS : High-speed video microscopy - High-speed photography - Microfoam dissipation in spray-applied coatings - Dissolution measurements - Determination of diffusion coefficients - Spray applications using CO2 and air |
| Permalink : |
https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=18606 |
in JOURNAL OF COATINGS TECHNOLOGY (JCT) > Vol. 66, N° 830 (03/1994) . - p. 27-39
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Reduction of air bubbles in spray-applied coatings in JOURNAL OF COATINGS TECHNOLOGY (JCT), Vol. 66, N° 830 (03/1994)
