Evaporation-induced foam stabilization in lubricating oils

Significance Mitigating lubricant foaming is of primary concern to lubricant manufacturers, as the control of deleterious foams is critical in high-performance applications. Facilitating the development of techniques to control foaming, the results from this research has identified that a special type of Marangoni flow driven by the differential evaporation of lubricant components plays a central role in promoting foaming in lubricant base oils. In addition, this research also shows that analyzing the stability of single bubbles can complement the foam stability data obtained from traditional bulk foam experiments. Hence, this paper provides physical insights into lubricant foaming and describes a convenient platform that lubricant manufacturers can use to develop better lubricants that are not susceptible to foaming.