Premium
Stability of multiple emulsions under shear stress
Author(s) -
Luhede Laura,
Wollborn Tobias,
Fritsching Udo
Publication year - 2020
Publication title -
the canadian journal of chemical engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.404
H-Index - 67
eISSN - 1939-019X
pISSN - 0008-4034
DOI - 10.1002/cjce.23578
Subject(s) - breakup , emulsion , materials science , pulmonary surfactant , drop (telecommunication) , breakage , shear stress , rheology , shear rate , composite material , capillary action , shear (geology) , chemical engineering , chromatography , chemistry , mechanics , mechanical engineering , physics , engineering
Multiple liquid emulsions of the water in oil in water (W 1 /O/W 2 ) type are used in a variety of consumer or technical applications, for instance in the encapsulation of certain active ingredients. The encapsulation process and release mechanisms of the inner phase of the carrier drops are important in order to properly process and formulate such liquid‐liquid systems. In this work the stability and breakage of multiple W 1 /O/W 2 emulsions under mechanical shear stress are investigated for emulsions with different surfactants and surfactant concentrations of the internal emulsion. Stressing the emulsions in a mechanical stirring process is compared to the membrane emulsification process. The membrane emulsification process results in higher encapsulation efficiencies than the stirring process. The emulsion droplets were subjected to shear stress below and above the critical capillary number for drop breakup. The results show that stable inner emulsions with sufficient surfactant concentrations increase the overall encapsulation efficiency for multiple emulsions subjected to shear stress, although the effect is not prominent. The depletion of the carrier oil droplets could be achieved for Ca numbers below the critical limit, reducing the encapsulation efficiency below 10 %. This shows that even a low shear stress can result in content release from the internal droplet phase. The experimental emulsion release study is supported by a numerical simulation of drop deformation and break‐up under shear stress.