Details

Autor(en) / Beteiligte

• Jørgensen, Loren
• Le Merrer, Marie
• Delanoë-Ayari, Hélène
• Barentin, Catherine

Titel

Yield stress and elasticity influence on surface tension measurements

Ist Teil von

• Soft matter, 2015-01, Vol.11 (25), p.5111-5121

Ort / Verlag

England: Royal Society of Chemistry

Erscheinungsjahr

2015

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• We have performed surface tension measurements on carbopol gels of different concentrations and yield stresses. Our setup, based on the force exerted by a capillary bridge on two parallel plates, allows us to measure an apparent surface tension of the complex fluid and to investigate the influence of flow history. More precisely the apparent surface tension measured after stretching the bridge is always higher than after compressing it. The difference between the two values is due to the existence of a yield stress in the fluid. The experimental observations are successfully reproduced with a simple elasto-plastic model. The shape of successive stretching-compression cycles can be described by taking into account the yield stress and the elasticity of the gel. We show that the surface tension γ LV of yield stress fluids is the mean of the apparent surface tension values only if the elastic modulus is high compared to the yield stress. This work highlights that measurements of thermodynamic quantities are challenged by the fluid out-of-equilibrium state implied by jamming, even at small scales where the shape of the bridge is driven by surface energy. Therefore setups allowing for deformation in opposite directions are relevant for surface tension measurements on yield stress fluids. Surface tension measurements are challenged by jamming in yield stress fluids, even at small scales. However our setup allowing opposite directions in deformation provides a method to deal with elastoplastic forces and measure the surface tension of yield stress fluids.