Three minimum wet thickness regions of slot die coating
| Autor: | Ping-Yao Wu, Hsien-Ming Chang, Ta-Jo Liu, Chi-Feng Lin, Yu-Rong Chang |
|---|---|
| Rok vydání: | 2007 |
| Předmět: |
Flow visualization
Materials science Capillary action business.industry Reynolds number engineering.material Capillary number Surfaces Coatings and Films Electronic Optical and Magnetic Materials Biomaterials Surface tension symbols.namesake Colloid and Surface Chemistry Optics Coating engineering symbols Fluid dynamics Meniscus Composite material business |
| Zdroj: | Journal of Colloid and Interface Science. 308:222-230 |
| ISSN: | 0021-9797 |
| DOI: | 10.1016/j.jcis.2006.11.054 |
| Popis: | An experimental study was carried out to determine the minimum wet thickness of slot die coating for low-viscosity solutions. There exist three distinct coating regions (I, II, and III), depending on the physical properties of the coating fluid, die geometry, and flow conditions. A critical Reynolds number was found, below which viscous and surface tension effects are important. In Region I, the minimum wet thickness increases with increasing capillary number and becomes independent of capillary number in Region II. Region III exists above the critical Reynolds number where fluid inertia is dominant. In this region, the minimum wet thickness decreases as Reynolds number increases. Flow visualization on the coating bead reveals that the position of the downstream meniscus of the coating bead determines the types of coating region, whereas the shape and position of the upstream meniscus determine the type of coating defects. It was also observed that the downstream meniscus was not located at the die lip corner and both the static and dynamic contact angles varied under different conditions. These findings are critical for realistic theoretical study of slot die coating. |
| Databáze: | OpenAIRE |
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