Instant yield stress measurement from falling drop size: The 'syringe test'
| Autor: | A. Geffrault, H. Bessaies-Bey, N. Roussel, P. Coussot |
|---|---|
| Rok vydání: | 2023 |
| Předmět: | |
| Zdroj: | Journal of Rheology. 67:305-314 |
| ISSN: | 1520-8516 0148-6055 |
| DOI: | 10.1122/8.0000557 |
| Popis: | We analyze different flow regimes of a filament formed by extrusion of a material through a cylindrical die. We deduce that the elongational yield stress of a simple yield stress fluid (i.e., with negligible thixotropy effects) can be determined from the mass of the droplet after filament breakage and an estimation of the critical radius at pinch-off at the solid-liquid regime transition. We demonstrate that such a simple characterization is relevant in a relatively wide range of extrusion velocities, i.e., this velocity slightly affects the drop mass in this range. For the simple yield stress fluids used, Carbopol gel, clay-water paste at different concentrations, and emulsion, covering a large range of yield stress values (50–1000 Pa), the elongational yield stress appears to be equal to the simple shear yield stress times a factor equal to about [Formula: see text]. As a consequence, this simple test may be used to obtain, almost instantaneously and without sophisticated apparatus (a syringe and a balance are sufficient), a good estimate of the shear yield stress of simple yield stress fluids. In that case, the main source of uncertainty (up to about 20%) is the value of the critical radius at the solid-liquid transition. Finally, we review the operating conditions (material properties and extrusion characteristics) for which we can expect this approach to be valid. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|