Effect of droplet size on the film formation of O/W emulsion

Purpose - The purpose of this study is to reveal the underlying mechanism in film formation of oil-in-water (O/W) emulsion. Design/methodology/approach - This study focuses on the film forming characteristics of O/W emulsion between the surface of a steel ball and a glass disc coated with chromium. The lubricant film thicknesses of O/W emulsion with various mechanical stirring strength were discussed, which were observed by technique of relative optical interference intensity. Findings - The authors directly observed the oil pool in the contact area, finding the size of oil pool was closely related to the film-forming ability of emulsion. Enrichment phenomenon occurs in oil pool, which was caused by phase inversion. Further investigations revealed that the emulsion is stable with strong stirring strength, resulting in a smaller oil pool size and worse film forming ability. Originality/value - With the wide usage of O/W emulsion in both biological and industrial systems, the ability of emulsion film formation is considered as an important factor to evaluate the lubrication effectiveness. Peer review - The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-12-2022-0354/