Synthesis and Application of Perfluoroalkyl Quaternary Ammonium Salts in Protein-Based Fire-Fighting Foam Concentrates

Nine perfluoroalkyl quaternary ammonium salts containing a perfluorinated tail were synthesized in order to evaluate their properties as additives in protein-based fire-fighting foam concentrates. They were obtained in high yield starting from (perfluoro-n-octyl)methyl oxirane via a two-step reaction scheme. Their structures were identified by Fourier-transform infrared spectroscopy and elemental analysis. Surface tension, interfacial tension, critical micellar concentration, and spreading coefficient of aqueous solutions of the synthesized compounds were first determined. Synthetic perfluoroalkyl quaternary ammonium salts were then added at reduced concentration (0.5 wt.%) to a commercial protein-based fire-fighting foam concentrate and their effects on foam spreading properties were further investigated via five specific laboratory tests: sealing time test, burn back time test, foam expansion test, drain time test, and foam flowing test. Results showed that the perfluoroalkyl quaternary ammonium salts strongly influence surface and extinguishing properties of protein-based fire-fighting foam concentrates, producing stable foams able to spread spontaneously over hydrocarbons and forming aqueous films with enhanced organic-vapor sealing properties.