MICELLAR LIFETIME: ITS RELEVANCE TO VARIOUS TECHNOLOGICAL PROCESSES

Abstract

The slow relaxation time (τ₂) of SDS micelles measured by pressure-jump technique was in the range of 10^-4 to 10⁺¹ seconds depending upon the surfactant concentration. We have studied how this five orders of change in micellar relaxation time, which is related to micellar lifetime, can influence various technological processes such as foaming, bubble dynamics, emulsification, wetting, detergency and rate of solubilization of oil in micellar solutions. A systematic research has been carried out to delineate the role of micellar lifetime on the dynamic processes in micellar solutions. The τ₂ SDS micelles was maximum at 200 mM concentration at 25°C, indicating that the most stable micelles were formed at this concentration. The most stable micelles at 200 mM SDS concentration resulted in the least foaming, the largest bubble size, the minimum frequency of bubble formation, the longest wetting time of textile, the largest emulsion droplet size in the mixture of hexadecane/SDS solutions and the most rapid solubilization of oil into micellar solutions. All these results were explained based on the flux of surfactant monomer from the bulk to the interface, which determined the dynamic surface tension of solution.