Abstract: A series of betaine short chain fluorocarbon surfactants grafted with carboxyl groups of different carbon chain lengths were selected, and the corresponding aqueous film foam extinguishing agent was prepared. The physicochemical properties of the mixed systems of fluorocarbon surfactants and sodium hexanesulfonate were studied, including surface activity, spreading ability, foaming property and fire extinguishing property of foam extinguishing agent. The results show that the critical micelle concentrations of the mixed systems were lower than 5.85 mmol/L, and the surface tension were lower than 19.71 mN/m. The mixed systems of the three surfactants can spread on the fuel surface, the foam expansion is over 7.1, and the 25% drainage time is not less than 3.27 min. The fire extinguishing time on fuels is less than 53 s while the burn-back time is more than 15.09 min. The results imply a potential application prospect of carboxy betaine short chain fluorocarbon surfactants in AFFFs.

Key words: aqueous film-forming foams, short chain fluorocarbon surfactant, carboxy betaine, surface activity, fire extinguishing agent