[article]
| Titre : |
Rheology and flow of paints in roll coating processes |
| Type de document : |
texte imprimé |
| Auteurs : |
Olivier Cohu, Auteur ; A. Magnin, Auteur |
| Année de publication : |
1997 |
| Article en page(s) : |
p. 102-107 |
| Note générale : |
Bibliogr. |
| Langues : |
Anglais (eng) |
| Tags : |
Peinturage 'Coil coating' Rouleau Ecoulement 'Propriété rhéologique' Peinture Etalement Feuil Epaisseur |
| Index. décimale : |
667.9 Revêtements et enduits |
| Résumé : |
The paints used in the coil-coating/roll-coating process often have a rheological behaviour of the thixotropic yieldstress type. This may be necessary in order to prevent the pigments from settling during storage. However, it has been shown that the structures responsible for this behaviour should be sufficiently fragile to be destroyed very quickly as the paint passes between two counter-rotating rolls, in spite of the brief period of time the fluid is subjected to stresses during this flow. It therefore follows that modelling the process with a view to predicting the thickness of the final coating may be based on a determination of the viscosity of the paints in a steady flow regime at 104 s−1, a result which was confirmed by coating experiments.
In contrast, the ability of a paint to level the defects that are inevitably generated on the liquid film is connected with its thixotropic properties. In order to obtain representative data, they must be measured during unsteady flow with a low rate of shear, following intense pre shearing. It has been shown that the kinetics of paint structure recovery, or recovery of viscosity, is of decisive importance. If this occurs too rapidly, a significant yield stress appears before the film is completely levelled, thus fixing the residual defects. The thixotropic properties, required to prevent sedimentation from occurring, must therefore be characterised by a sufficiently slow structure recovery time. |
| Note de contenu : |
- Analysis of the oil-coating processNALYSYS OF THE OIL-COATING PROCESS
- STEADY-STATE RHEOLOGY OF PAINTS
- BEHAVIOUR OF PAINTS FLOWING BETWEEN TWO COUNTER-ROTATING ROLLS
- APPLICATION TO THE PREDICTION OF COATING THICKNESS
- RHEOLOGY OF PAINTS AND FILM LEVELLING |
| Permalink : |
https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=17152 |
in SURFACE COATINGS INTERNATIONAL > Vol. 80, N° 3 (03/1997) . - p. 102-107
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Rheology and flow of paints in roll coating processes in SURFACE COATINGS INTERNATIONAL, Vol. 80, N° 3 (03/1997)
