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UBC Theses and Dissertations
Capillary menisci between particles absorbed at a liquid-fluid interface Hou, Linda
Abstract
One aspect of the stability of solids-stabilized emulsions was indicated by Denkov et al. (8) who reported that the capillary pressure required for an emulsion droplet’s liquid to squeeze between the interfacial particles and come into contact with another droplet’s free liquid interface must be overcome and provides a barrier to the thinning of the film between droplets. In light of the work done by Denkov et al., the objective of the thesis has been to determine the effect several factors such as particle size, separation distance, wettability, fluid properties, and contact angle hysteresis have on emulsion stability, represented in terms of capillary pressures, using a two-layer particle model for coalescence. Two general models were developed, one which is based on a uniform layer of spherical particles adsorbed on a fluid-fluid interface, and the other, a two dimensional analogue, in which parallel, horizontal cylinders are situated on the interface. Numerical techniques were applied in the solution of both models since no simplification was made by the neglect of gravity as is found in similar models (8, 11, 12). As a consequence, the models can be used to describe macroscopic systems whose characteristic dimensions are well above the micron scale. A corresponding experimental system employing parallel cylinders was then constructed and used to generate capillary pressures and meniscus profiles for comparison with the computed model results. The model results agree with the experimental findings in the literature that the smaller the particles, the closer the packing of particles, or the rougher the solids are, the more stable the emulsions. Furthermore, a decrease in the Bond number or a decrease in wettability of the particles to the disperse phase would increase stability based on capillary pressure considerations. Overall trends for the cylinders model and the spheres model were similar. The contact angles which yield optimal stability from capillary and thermodynamic considerations lie in the range of 90°≤θ≤180°. The study revealed that good agreement between the model and the experimental measurements was obtained when apparent contact angles, which take into account hysteresis, were used to generate the model profiles for each meniscus.
Item Metadata
Title |
Capillary menisci between particles absorbed at a liquid-fluid interface
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
1993
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Description |
One aspect of the stability of solids-stabilized emulsions was indicated by Denkov et al. (8) who reported that the capillary pressure required for an emulsion droplet’s liquid to squeeze
between the interfacial particles and come into contact with another droplet’s free liquid interface
must be overcome and provides a barrier to the thinning of the film between droplets. In light of
the work done by Denkov et al., the objective of the thesis has been to determine the effect several
factors such as particle size, separation distance, wettability, fluid properties, and contact angle
hysteresis have on emulsion stability, represented in terms of capillary pressures, using a two-layer
particle model for coalescence.
Two general models were developed, one which is based on a uniform layer of spherical
particles adsorbed on a fluid-fluid interface, and the other, a two dimensional analogue, in which
parallel, horizontal cylinders are situated on the interface. Numerical techniques were applied in
the solution of both models since no simplification was made by the neglect of gravity as is found
in similar models (8, 11, 12). As a consequence, the models can be used to describe macroscopic
systems whose characteristic dimensions are well above the micron scale. A corresponding
experimental system employing parallel cylinders was then constructed and used to generate
capillary pressures and meniscus profiles for comparison with the computed model results.
The model results agree with the experimental findings in the literature that the smaller the
particles, the closer the packing of particles, or the rougher the solids are, the more stable the
emulsions. Furthermore, a decrease in the Bond number or a decrease in wettability of the
particles to the disperse phase would increase stability based on capillary pressure considerations.
Overall trends for the cylinders model and the spheres model were similar. The contact angles
which yield optimal stability from capillary and thermodynamic considerations lie in the range of
90°≤θ≤180°. The study revealed that good agreement between the model and the experimental
measurements was obtained when apparent contact angles, which take into account hysteresis,
were used to generate the model profiles for each meniscus.
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Extent |
5038302 bytes
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Genre | |
Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-02-23
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0050437
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
1994-05
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Item Media
Item Citations and Data
Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.