Investigation of oil-in-water emulsion stability with relevant interfacial characteristics simulated by dissipative particle dynamics

Oil-in-water (O/W) emulsions were prepared by using non-ionic surfactants, Tween 80 and Span 20, and the stability of the emulsions was investigated under conditions of varied HLB, emulsifier concentration, stirring time and stirring intensity. It was found that the HLB of emulsifier has a significant effect on the emulsion stability. Moreover, the structures and properties of the interfacial film formed by emulsifier molecules with different HLB were characterized by dissipative particle dynamics (DPD) simulations. The results show that the interfacial film thickness increases with the HLB values changing from 9 to 15, while the most stable emulsion appears when HLB is 13 with the minimum interfacial tension. Neither too small nor too large oil droplet size, determined by molecular volume of emulsifier as well as the volume ratio of hydrophilic head and hydrophobic tail, could improve the emulsion stability when the preparation technology is the same. Therefore, the influence of HLB on the emulsion stability is essentially affected by the comprehensive result of interfacial film thickness, interfacial tension and molecular structure of emulsifier. This study could contribute to the development of controlling and preparation of emulsions with suitable stability from the point of view of emulsifier.