DYNAMIC BEHAVIOR AND DETERGENCY IN SYSTEMS CONTAINING NONIONIC SURFACTANTS AND MIXTURES OF POLAR AND NONPOLAR OILS

Videomicroscopy was used to observe the dynamic behavior that occurred when aqueous solutions of nonionic surfactants were brought into contact with oils containing various proportions of n-hexadecane and oleyl alcohol. A new contacting technique was used in which a single oil drop was injected into a surfactant solution. Under lipophilic conditions where the surfactant is preferentially soluble in the nonaqueous phase, the drop experienced significant swelling as it took up surfactant and water. Eventually, it reached a composition where the lamellar liquid crystalline phase began to develop at the interface as myelinic figures growing toward the aqueous solution. A quasi-steady-state analysis was developed that was able to explain the effects of such variables as initial drop size and initial surfactant concentration on the time until liquid crystal formation began. The relationship of the results to detergency is discussed. It appears that a major mechanism of detergency for oils containing more than about 10% polar material under lipophilic conditions is solubilization into an intermediate lamellar phase which is dispersed into the washing bath as agitation breaks up the myelinic figures.