Optimization of external oil phase systems by differential thermal analysis

The stability of emulsions is, in most cases, linked to the homogeneity and fineness of dispersed particles. For external oil phase systems, surfusion temperature and disperse-phase water-particle crystallization kinetics are particle-size dependent, according to a statistical probability function, f 1 = 1/ N 1 ʃ D 0 d N where N 1 is the number of particles, and D is the diameter. DTA, Investigation of emulsion size distribution by surfusion thermograms, and dispersed phase crystallization kinetics (observed during freeze-thaw cycles with isotherm plateau), can be helpful in the choice of surfactant, coupling agents and raw materials and can provide an approach for estimation of the stability of w/o emulsions. This method has also been applied to technological procedure optimization and quality control of end products. Retained optimization criteria are, in decreasing order of importance, a very low polydispersity and a particle-size distribution as near Gaussian distribution as possible. Surfusion temperature, which varies from one system to another (−10 to −47°C), must remain stable with time or after the ageing process.