Micro-structure characteristics and the fire-extinguishing performance of aqueous film-forming foam mixed with short-chain fluorocarbon surfactant

The environmental persistence of perfluorinated compounds derived from long-chain fluorocarbon surfactants in aqueous film-forming foam (AFFF) necessitates the development of eco-friendly alternatives. The short-chain fluorocarbon surfactants (C < 8) are promising substitutes due to their reduced bioaccumulation potential while maintaining surface activity. An amphoteric short-chain fluorocarbon surfactant, namely Capstone® FS-50 (FS-50), was used in this study. The micro-structure characteristics and fire-extinguishing performance of the AFFF mixed with FS-50 was evaluated systematically. By comparing the foaming ability, bubble distribution, liquid drainage rate and bubble size, the test results indicate that the addition FS-50 can effectively delay the burst rate of the foam, and the foaming ability can also improve slightly. This feature can effectively improve fire-extinguishing performance, the fire extinguishing time has been reduced by 60%. On this basis, the relationship between the ambient velocity and fire-extinguishing time was explored. The fire-extinguishing time and the temperature reduction rate are also no longer change when the ambient velocity exceeds 2.5 m/s. Finally, a new prediction model of fire-extinguishing efficiency based on the fire-extinguishing time and temperature change rate was proposed to evaluate the fire-extinguishing performance of foam with different components. These findings provide critical insights into the effect of short-chain fluorocarbon surfactant in AFFF and establish a framework for evaluating AFFF performance in real fire scenarios, advancing the development of environmentally sustainable fire-fighting agents.