MEASUREMENT OF THE SURFACE DILATATIONAL VISCOSITY OF AQUEOUS GELATIN SURFACTANT SOLUTIONS

A new method for the measurement of the interfacial dilatational viscosity has been developed and was used to determine the surface dilatational viscosity of gelatin-surfactant solutions. The mathematical analysis and correlations of the results are included. Experimental results on interfacial dilatational viscosity are very limited, and there are no systematic studies available on the surfactant concentration and temperature dependence of interfacial dilatational viscosity. The surface dilatational viscosity of the phase interface formed between gelatin-surfactant solutions and air was determined as function of surfactant concentration at various temperatures by means of a bubble growth device, designed and constructed in our laboratory. The surface dilatational viscosity of the gelatin-surfactant solutions was found to increase with temperature and exhibited a minimum at the critical micelle concentration for all temperatures investigated. Although we assume negligible surface tension variation effects which may be utilized only in certain systems, the method does provide a direct measurement of the dilatational viscosity, not coupled with the surface shear viscosity. © 1991.