45 research outputs found
Using cupriethylenediamine (CED) solution to decrease cellulose fibre network strength for removal of pulp fibre plugs
Sorption and Interfacial Rheology Study of Model Asphaltene Compounds
The
sorption and rheological properties of an acidic polyaromatic
compound (C5PeC11), which can be used to further our understanding
of the behavior of asphaltenes, are determined experimentally. The
results show that C5PeC11 exhibits the type of pH-dependent surface
activity and interfacial shear rheology observed in C<sub>6</sub>-asphaltenes
with a decrease in the interfacial tension concomitant with the elastic
modulus when the pH increases. Surface pressure–area (Π–<i>A</i>) isotherms show evidence of aggregation behavior and π–π
stacking at both the air/water and oil/water interfaces. Similarly,
interactions between adsorbed C5PeC11 compounds are evidenced through
desorption experiments at the oil/water interface. Contrary to indigenous
asphaltenes, adsorption is reversible, but desorption is slower than
for noninteracting species. The reversibility enables us to create
layers reproducibly, whereas the presence of interactions between
the compounds enables us to mimic the key aspects of interfacial activity
in asphaltenes. Shear and dilatational rheology show that C5PeC11
forms a predominantly elastic film both at the liquid/air and the
liquid/liquid interfaces. Furthermore, a soft glassy rheology model
(SGR) fits the data obtained at the liquid/liquid interface. However,
it is shown that the effective noise temperature determined from the
SGR model for C5PeC11 is higher than for indigenous asphaltenes measured
under similar conditions. Finally, from a colloidal and rheological
standpoint, the results highlight the importance of adequately addressing
the distinction between the material functions and true elasticity
extracted from a shear measurement and the apparent elasticity measured
in dilatational–pendant drop setups
Van der Waals Emulsions: Emulsions Stabilized by Surface-Inactive, Hydrophilic Particles via van der Waals Attraction
© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Surface-inactive, highly hydrophilic particles are utilized to effectively and reversibly stabilize oil-in-water emulsions. This is a result of attractive van der Waals forces between particles and oil droplets in water, which are sufficient to trap the particles in close proximity to oil–water interfaces when repulsive forces between particles and oil droplets are suppressed. The emulsifying efficiency of the highly hydrophilic particles is determined by van der Waals attraction between particle monolayer shells and oil droplets enclosed therein and is inversely proportional to the particle size, while their stabilizing efficiency is determined by van der Waals attraction between single particles and oil droplets, which is proportional to the particle size. This differentiation in mechanism between emulsification and stabilization will significantly advance our knowledge of emulsions, thus enabling better control and design of emulsion-based technologies in practice