THIN LIQUID-FILMS IN A NONAQUEOUS MEDIUM

Foams and froths are important in many industrial product and process technologies. Whilst a stable, long-lasting foam is sometimes desirable, in many instances a stable foam is exactly what is not wanted. Interference microscopy has been used to measure thin liquid film thickness profiles, rupture thicknesses and bubble lifetimes of air bubbles in diesel fuel. The surface rheological properties of the diesel fuel/air interface have also been measured using surface light scattering. The measurements have indicated that the addition of a fluorosilicone antifoam agent to diesel fuel resulted in a highly rigid interface which irreversibly ruptures if sufficient force is applied. Further, the antifoam acted as a pro-foamer, depending on bubble size. A mechanism of action for the antifoam agent is proposed which is consistent with these measurements.