COMPARISON OF LIGHT MICROSCOPY AND PARTICLE SIZE DISTRIBUTION MEASUREMENTS TO DETERMINE COMMERCIAL EMULSION STABILITY

摘要

Emulsions are comprised of two phases that are normally immiscible. Oil-in-water emulsions contain oil as the dispersed phase and water as the continuous phase, as well as a surfactant/emulsifier which lowers the interfacial tension of the two phases and stabilizes the system to an extent. Macro-emulsions are kinetically and thermodynamically unstable. As a result, the emulsion will revert to the two phases from which it was formed over time. The main mechanism for the loss of stability in macro-emulsions is coalescence. Modifications can be made to an emulsion to increase its stability, namely the addition of polymeric surfactants, thickeners and other co-surfactants. The stability of an emulsion can be determined by obtaining its droplet size distribution over time to calculate its apparent coalescence rate. The Malvern Mastersizer 3000 uses light scattering technology to determine the droplet size distribution of emulsions. The apparent coalescence rate is then calculated from Equation 1 where d_(50) at t = 0 is the mean droplet diameter when the emulsion is made and d_(50) at t is the mean droplet diameter at time = t in weeks.