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Assessment of the accuracy and precision of surface and interfacial viscosities measured with rotating and oscillating DuNouy ring geometry

Historically, the DuNouy ring has been used to measure surface tension of liquids. Recently, this ring has been reported to be used to measure surface viscosity with rotational rheometers. Surface rheometry measurements are much more difficult experiments compared to bulk rheometry tests. This is primarily, due to the ultra low torques that need be measured or applied. Furthermore, it is not correct to assume Newtonian flow behavior, and that secondary flows are not present. This presentation reports on a study to determine the accuracy of the DuNouy ring to measure surface viscosity. Experiments were performed on stearic acid films spread over the surface of water. The accuracy of these data is compared with well documented literature values.

Type:	Rheology
Duration:	29 minutes
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