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Rheo‐optical determination of the interfacial tension in a dispersed blend
Author(s) -
Tassieri Manlio,
Grizzuti Nino,
Greco Francesco
Publication year - 2003
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/masy.200350806
Subject(s) - surface tension , drop (telecommunication) , spinning drop method , materials science , shearing (physics) , capillary action , mechanics , rheology , shear thinning , newtonian fluid , optics , shear (geology) , composite material , thermodynamics , physics , mechanical engineering , engineering
In this work, we present two novel methods to determine the interfacial tension of a disperse polymer blend through rheo‐optical measurements of flow‐induced single drop distortions. A counter‐rotating shearing device with transparent plates is used to measure drop distortions. The cell geometry allows for a top view of the deforming drop, i.e., along the velocity gradient direction. Such a view is the only possible option for all currently available commercial rheo‐optical instruments. Two different quantities are monitored, namely, the drop axis along the vorticity direction, and the rotation period of the drop surface. We use drops of a polyacrilamide aqueous solution (a shear thinning liquid) immersed in a polyisobutene matrix. Experimental results are interpreted in terms of theories for Newtonian liquids, where the relevant parameter is the Capillary number. If an appropriate viscosity ratio is chosen, that accounts for the shear thinning behaviour of the drop phase, good agreement is found between measurements and theoretical predictions. As a result, a robust estimate of the blend interfacial tension, that makes use only of the information acquired from top view experiments, is obtained.