Effect of a Surfactant Mixture on Coalescence Occurring in Concentrated Emulsions: The Hole Nucleation Theory Revisited

By conducting both a bottle test and isolate drop–drop experiments, we determine the coalescence rates of water droplets within water-in-oil emulsions stabilized by a large amount of Span 80 in the presence of Tween 20, a surfactant that acts as a demulsifier. Using a microscopic model based on a th...

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Bibliographic Details
Published in:Langmuir 2021-07, Vol.37 (29), p.8726-8737
Main Authors: Dinh, Huy-Hong-Quan, Santanach-Carreras, Enric, Lalanne-Aulet, Marie, Schmitt, Véronique, Panizza, Pascal, Lequeux, François
Format: Article
Language:English
Subjects:
Chemical Sciences
Physics
Polymers
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Summary:By conducting both a bottle test and isolate drop–drop experiments, we determine the coalescence rates of water droplets within water-in-oil emulsions stabilized by a large amount of Span 80 in the presence of Tween 20, a surfactant that acts as a demulsifier. Using a microscopic model based on a theory of hole nucleation, we establish an analytical formula that quantitatively predicts the coalescence frequency per unit area of droplets whose interfaces are fully covered by surfactant molecules. Despite its simplicity and the strong assumptions made for its derivation, this formula captures our experimental findings on Span 80-stabilized emulsions as well as other results, found in the literature, remarkably well on a wide range of water-in-crude oil systems.
ISSN:0743-7463
1520-5827
DOI:10.1021/acs.langmuir.1c00975