Experimental Investigation of Stability of Emulsions Produced by Catastrophic Phase Inversion Using Non-Ionic Surfactants

Emulsions stabilized by environmentally friendly surfactants have been at the center of research attention over recent decades. Non-ionic surfactants with good biodegradability, while being non-toxic and non-irritating, have dominated in this area. For a chosen system, the main goal is to engineer its properties for smaller droplet sizes and better stability, a process which is mainly derived from the emulsification method. In the present study, Ethylan 1005 and Ethylan 1008 were used as stabilizers, both alone and combined at different ratios, in eco-friendly emulsions produced by paraffin oil and Millipore water, via direct emulsification, catastrophic phase inversion and catastrophic phase inversion in droplets. During the experiments, the emulsions’ rheological behavior, phase separation, and droplet size distribution profiles were measured. Catastrophic phase inversion in droplets resulted in the finest droplet size distributions for both emulsifiers when used alone. As the concentration of Ethylan 1008 increased from 0% to 100% in the surfactant mixtures, the droplets’ mean diameter and range also increased, indicting degradation of emulsion stability. However, phase separation tests revealed the opposite. Explanation was found in the chemical structure of the two emulsions and the steric phenomena caused by this, while a semi-quantitative analysis of these trends was also developed.