Experimental study on thermal stability and burn-back performance of aqueous film forming foam agent(AFFF) with short-chain fluorocarbon surfactant or flame retardant

Long-chain fluorocarbon surfactant is widely used in aqueous film-forming AFFF due to its excellent interfacial property. It can effectively improve the extinguishing efficiency of foam by improving the stability of foam. However, due to its severity environmental damage, some studies in recent years have focused on using short-chain fluorocarbon surfactants or flame retardants to replace long-chain fluorocarbon surfactants. However, the stability mechanism of foam after adding new additives and its performance in high-temperature thermal radiation environment are still unclear and require further clarification. Therefore, in this work, the effect of different additives on the interfacial properties of foam solution, foaming ability and foam stability, thermal stability and burn-back performance under the heat radiation environment are discussed. The results indicate that the thermal stability and burn-back performance of AFFF mixed with long-chain fluorocarbon surfactant (FS-30) or flame retardant (APP and MCA) was not significantly improved. However, the foam mixed with FS-50 exhibits excellent thermal stability and burn-back performance, it could be a proper substitute for long-chain fluorocarbon surfactants to be used in the AFFF mixed system. Through exploring the adsorption behavior of surfactant molecules on the liquid-air interface of the foam, FS-50 molecules and hydrocarbon surfactant molecules have a strong synergistic effect, which making it more difficult for water molecules to enter the surface of the mixed system. and the stability of foam will be enhanced. Besides, the proper mass concentration will also affect the interfacial properties of foam solution, foaming ability and foam stability, thermal stability and burn-back performance of the foam in fire environment, the mass concentration of additive in the foam solution should be remained at 0.3wt.%.