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Effect of high shearing on the rheological/structural properties of highly concentrated w/o emulsions
Author(s)
Yakhoub, Hamat Abderrahmane
Date Issued
2009
Type
Thesis
Publisher
Cape Peninsula University of Technology
Abstract
Emulsion explosives are classified as highly concentrated water-in-oil emulsions with high
droplet volume fraction that exceeding the close packing limit of spherical droplets. These
emulsions are commonly used as re-pumpable materials. Thus, the shearing action resulting
from the transportation process of these materials has a tremendous impact on their
structures and functionality and might reduce the shelf-life and performance of the products.
Therefore the main goal of this research was to investigate the stability of highly
concentrated water-in-oil emulsion under shearing using a newly designed piston-pumping
instrument.
The results of measurement included the droplet size distribution, microscopic observation,
flow and viscoelastic properties of the materials. Neither crystallisation nor other
destabilisation phenomena such as coalescence, partial coalescence, or phase inversion
occurred during the shearing process of these emulsions, regardless of their formulation
content. It was found that the high shearing action within this research experimental window
induced droplet refinement. The changes in droplet size distribution were achieved by multipass
flow through a small orifice set as outlet of the piston-chamber pumping instrument,
and intensive shearing provided the shift of the droplet sizes to the smaller-size side of the
distribution. Their distributions were wider and of Gaussian type. Two models were proposed
and used to fit the refinement evolution and the width of distributions respectively.
droplet volume fraction that exceeding the close packing limit of spherical droplets. These
emulsions are commonly used as re-pumpable materials. Thus, the shearing action resulting
from the transportation process of these materials has a tremendous impact on their
structures and functionality and might reduce the shelf-life and performance of the products.
Therefore the main goal of this research was to investigate the stability of highly
concentrated water-in-oil emulsion under shearing using a newly designed piston-pumping
instrument.
The results of measurement included the droplet size distribution, microscopic observation,
flow and viscoelastic properties of the materials. Neither crystallisation nor other
destabilisation phenomena such as coalescence, partial coalescence, or phase inversion
occurred during the shearing process of these emulsions, regardless of their formulation
content. It was found that the high shearing action within this research experimental window
induced droplet refinement. The changes in droplet size distribution were achieved by multipass
flow through a small orifice set as outlet of the piston-chamber pumping instrument,
and intensive shearing provided the shift of the droplet sizes to the smaller-size side of the
distribution. Their distributions were wider and of Gaussian type. Two models were proposed
and used to fit the refinement evolution and the width of distributions respectively.
Additional information
Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2009.
Subjects
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203034031_Yakhoub_HA_Mtech_Chemical Engineering_Eng_2009_9002289.pdf
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Thesis
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