Oil resistivity of fluorine-free foams stabilized by nanoparticles and surfactants

Abstract This study aims at exploring fluorine-free foam properties co-stabilized by nanoparticles (NPs) and surfactant. The mixed disperse liquids composed of silica NPs, nonionic hydrocarbon surfactant (APG-0810), and organosilicon surfactant (CoatOsil-77) was prepared. The NP-intensified foams under the action of n-heptane (flammable liquid) were focused by analyzing aggregation behavior of surfactants, initial foaming height, foams drainage and decay, and single vertical film stability of the mixed disperse liquids. The findings show that the presence of n-heptane shows an obvious effect on adsorption behavior of surfactant. After n-heptane is added, the surface tension and viscosity of the mixed dispersion liquid increases, but the conductivity and foaming ability decreases. In addition, the presence of NPs with low concentration or n-heptane accelerates foam drainage and volume decay. The vertical liquid film thickness also declines at the presence of n-heptane. NPs can improve oil resistivity of foam to a certain extent, and the more the NP concentration, the better the oil resistivity. This study can provide theoretical guidance for the development of new fluorine-free foams used for liquid fuel fire.