Targeted Interfacial Rheology for Fluorine-Free Firefighting Foams

Class-B firefighting foams are aqueous foams that spread over liquid fuel and extinguish fires. Recent regulations require per- and polyfluoroalkyl substance (PFAS)-free formulations for these fire suppressants. However, identifying non-PFAS surfactant or surfactant mixtures that combines the necessary low surface tensions against fuel and air to form an aqueous film is a significant hurdle; hence new paradigms and formulations to suppress fuel fires are urgently needed. This talk will highlight the aims and current efforts to aid in the identification and development of PFAS-free firefighting formulations from mixtures of soluble mixed charged surfactants, which are capable of synergistically lowering the surface tension and the critical micelle concentration. Fundamental rheology-based design principles for formulating surfactant systems that enhance foam stability against coarsening and coalescence will be presented. In addition, results to date for characterizing surfactant thermodynamic and transport properties at interfaces and foam stability will be shown.