Surface tension measurements of viscous materials by pendant drop method: time needed to establish equilibrium shape

0504710 - ÚMCH 2020 RIV DE eng C - Konferenční příspěvek (zahraniční konf.)
Jůza, Josef
Surface tension measurements of viscous materials by pendant drop method: time needed to establish equilibrium shape.
Macromolecular Symposia. Volume 384, Issue 1. Weinheim: WILEY-VCH Verlag, 2019 - (Lach, R.; Langer, B.; Michel, P.), Roč. 384, č. 1 (2019), s. 1-12, č. článku 1800150. ISSN 1022-1360.
[PolyMerTec18. Merseburg (DE), 13.06.2018-15.06.2018]
Grant CEP: GA MŠMT(CZ) LO1507
Institucionální podpora: RVO:61389013
Klíčová slova: interfacial tension * measurement error * pendant drop
Obor OECD: Polymer science

The pendant drop method of surface tension measurements published in 1938 has been frequently used since late 1960s. The time to reach equilibrium drop shape for viscous materials was mentioned in few papers only. The aim of this paper is to estimate time needed to reach a shape sufficiently close to equilibrium as a function of required precision and material viscosity. The procedure is based on Roe's error analysis of the pendant drop method and on a prerequisite of similarity in relaxation times of pendant drop and that of ellipsoid droplet published by Luciani and Utracki. An equation for time needed to reach equilibrium shape of pendant drop has been derived. Estimates have been verified through measurements of a test liquid, strong correction using empirical coefficients is needed to predict equilibration times correctly. The formula found is useful to assess whether the measurement can be accomplished before the material starts to degrade or otherwise change significantly. Since approximation using formula for ellipsoid relaxation is a weak point of the estimate, the challenge remaining for future is to describe the relaxation of pendant drop.
Trvalý link: http://hdl.handle.net/11104/0296291