Evolution of the Size Distribution of Oil-droplets Over Time in Oil-in-water Emulsions

A theoretical method to calculate the evolution of the size distribution of oil-droplets in O/W emulsions over time was proposed based on the model where the coalescence rate of two oil-droplets was expressed by second-order kinetics using the rate constant evaluated from the activation energy for coalescence. The force between two oil-droplets of different diameters was appropriated by the force between two oil-droplets of equivalent diameter, and the increase in the rate of the number density of oil-droplets was estimated by solving the mass balance equation. The evolution of the size distribution of oil-droplets in several conditions agreed well with well-known features of coalescence of oil-droplets in O/W emulsion such as instability with larger oil-droplet size.