Tuning foam stability under flammable liquid fuel by inorganic nanoparticles

Foam stability under fuel action is one of the key parameters for firefighting foams to fight flammable liquid fuel fires with high efficiency. Foams stabilized by inorganic nanoparticles have promising applications in the development of environmentally friendly firefighting foams. This paper focuses on tuning foam stability under fuel action of environmentally friendly firefighting foams by inorganic nanoparticles. The foam dispersions were prepared with silica nanoparticles (nano-silica), short-chain fluorocarbon surfactants (FS-50), and nonionic hydrocarbon surfactants (APG-0810). Under fuel (n-heptane) action, the interaction of surfactants, nano-silica, and n-heptane, and the foam decay, foam drainage, and foam film stability of foam dispersions were investigated. Results indicated that nano-silica, surfactants, and n-heptane have strong interactions. With the increasing nano-silica concentration, the surface tension and viscosity of foam dispersions increased, and the conductivity and foaming ability decreased. Nano-silica can effectively delay drainage and volume decay of APG-0810/FS-50 foam under liquid fuel, and the effect is more obvious with the increase of nano-silica concentration. Furthermore, the single vertical film thinning dynamic is accelerated as fuel is added but decelerated as nano-silica concentration increases. Under n-heptane action, the optimum nano-silica concentration for improving foam stability is 5 %. The results of this paper can further enrich the studies of environmentally friendly firefighting foam stabilized by nanoparticles under fuel action.