Effect of liquid fuel on foamability and foam stability of mixtures of fluorocarbon and hydrocarbon surfactants

The oil resistivity of aqueous foam is a significant property in many industrial fields. This work aims at studying on oil resistivity of foams generated by mixtures of fluorocarbon and hydrocarbon surfactants, the critical components of firefighting foams. Four kinds of foam solutions were prepared to contain a short-chain fluorocarbon surfactant (FS-50) and four hydrocarbon surfactants with different ionic types, including anionic (SDS), cationic (CTAB), zwitterionic (CAD-40), and nonionic (APG-0810). The effects of the typical liquid fuel (n-heptane) on solution properties, foamability, foam stability, and film stability were studied deeply. The results show that foamability and foam stability were significantly influenced by the addition of n-heptane. The addition of n-heptane leads to significant decrease in foamability of all four foam solutions. The foam volume decay and drainage of all four solutions were accelerated under the action of n-heptane. The film stability of all four solutions decreased upon the presence of n-heptane. The mixture of APG-0810/FS-50 showed the best ability to inhibit liquid fuel. The study can promote the use of mixtures of hydrocarbon and fluorocarbon surfactants in the development of firefighting foams used to extinct liquid fuel fires.