Nanoemulsion stability: experimental evaluation of the flocculation rate from turbidity measurements.

The coalescence of liquid drops induces a higher level of complexity compared to the classical studies about the aggregation of solid spheres. Yet, it is commonly believed that most findings on solid dispersions are directly applicable to liquid mixtures. Here, the state of the art in the evaluation of the flocculation rate of these two systems is reviewed.

Lifetime of oil drops pressed by buoyancy against a planar interface: large drops.

In a previous report [C. Rojas, G. Urbina-Villalba, and M.

Lifetime of micrometer-sized drops of oil pressed by buoyancy against a planar interface.

Emulsion stability simulations are used to estimate the coalescence time of one drop of hexadecane pressed by buoyancy against a planar water/hexadecane interface. In the present simulations, the homophase is represented by a big drop of oil at least 500 times larger than the approaching drop (1-10 microm). Both deformable and nondeformable drops are considered along with six different diffusion tensors.

Influence of droplet deformability on the coalescence rate of emulsions.

In this article the influence of deformation on the coalescence rates of oil-in-water (O/W) emulsions is analyzed. Calculations for doublets and many-particles systems were performed based on a Brownian dynamics algorithm. Extensional and bending energies were included in order to quantify the effect of the changes in the surface geometry on the coalescence rates.

Influence of flocculation and coalescence on the evolution of the average radius of an O/W emulsion. Is a linear slope of R3 vs. t an unmistakable signature of Ostwald ripening?

The LSW theory of Ostwald ripening, predicts a linear variation of the cube of the average radius of a dispersion as a function of time (R(3)vs. t) [I. M.

An algorithm for emulsion stability simulations: account of flocculation, coalescence, surfactant adsorption and the process of Ostwald ripening.

The first algorithm for Emulsion Stability Simulations (ESS) was presented at the V Conferencia Iberoamericana sobre Equilibrio de Fases y Diseño de Procesos [Luis, J.; García-Sucre, M.; Urbina-Villalba, G.

Theoretical estimation of stability ratios for hexadecane-in-water (H/W) emulsions stabilized with nonylphenol ethoxylated surfactants.

The effect of steric interactions on the stability of oil-in-water emulsions is studied here by means of emulsion stability simulations (ESS). For this purpose, a new steric potential based on a modification of the one formerly proposed by Vincent et. al.

Steric interaction between spherical colloidal particles.

The reliability of the Derjaguin approximation for the calculation of the mixing term between sterically stabilized colloidal particles is studied. For this purpose, the steric potential obtained from the experiment of Doroszkowski and Lambourne [J. Polym.

Interfacial energy and the law of corresponding states 2: associated fluids.

A mesoscopic model for the liquid/vapor interface previously developed for nonpolar fluids [J. Phys. Chem.

Role of the secondary minimum on the flocculation rate of nondeformable droplets.

The kinetic stability of suspensions is usually associated with a decrease in the flux of flocculating particles due to the action of a repulsive potential. However, previous calculations on bitumen drops suggest the possible occurrence of relatively fast aggregation rates in systems with large electrostatic barriers for primary minimum flocculation. This indicates a strong effect of the secondary minimum in the process of aggregation.

Effect of dynamic surfactant adsorption on emulsion stability.

The effect of dynamic surfactant adsorption on the stability of concentrated oil in water emulsions is studied. For this purpose, a modification of the standard Brownian dynamics algorithm (Ermak, D.; McCammon, J.

Calculation of flocculation and coalescence rates for concentrated dispersions using emulsion stability simulations.

A simple procedure for the quantification of flocculation (k(f)) and coalescence (k(c)) rates from emulsion stability simulations (ESS) of concentrated systems is presented. It is based on a simple analytical equation, which results from the sum of well-known formulas for the separate processes of flocculation and coalescence. The expression contains k(f) and k(c) as fitting parameters and is found to reproduce the behavior predicted by ESS spanning a wide range of volume fractions (1 < phi < 30%) and surfactant concentrations (1.

Average hydrodynamic correction for the Brownian dynamics calculation of flocculation rates in concentrated dispersions.

In order to account for the hydrodynamic interaction (HI) between suspended particles in an average way, Honig et al. [J. Colloid Interface Sci.