Environmentally Friendly Firefighting Foams Used to Fight Flammable Liquid Fire

The application of conventional aqueous film-forming foam (AFFF) has been restricted due to the environmental hazards caused by long-chain fluorocarbon surfactants. Environmentally friendly firefighting foams are urgently needed. In this study, AFFFs based on a long-chain fluorocarbon surfactant and a short-chain fluorocarbon surfactant, and fluorine-free foams based on a silicone surfactant and a mixture of foam stabilizers are prepared. The critical properties, including film-forming ability, foam stability, and foam spreading property, of foams and a commercial AFFF are investigated systematically. The fire extinguishing and burn-back performances are evaluated by a small-scale test method. Results indicate that the removal of fluorocarbon surfactants from AFFF leads to an apparent decrease in film-forming ability, foam stability, foam spreading property, and corresponding fire extinguishing performance. AFFF based on short-chain fluorocarbon surfactant shows excellent extinguishing and burn-back performances even if its film-forming ability, foam stability, and foam spreading are slightly worse than those of conventional AFFF. Although FfreeF cannot form an aqueous film and exhibits poor foam spreading, it demonstrates satisfactory fire extinguishing performance and optimal burn-back performance depending on its superhigh stability. This study can provide guidance in the development of environmentally friendly firefighting foams.