Experimental Study on Foam Drainage of AFFF: Additive Regulation, Thermal Transition, and Fire-Extinguishing Verification

Abstract Foam drainage is crucial for maintaining foam layer stability and improving the efficiency of aqueous film-forming foam (AFFF) in extinguishing oil fires. This paper investigates the drainage kinetics of AFFF to reveal how formulation and temperature regulate drainage, establish a quantitative relationship between drainage rate and fire-extinguishing performance, and thereby provide a basis for designing high-efficiency and eco-friendly AFFF. The experimental results show that the hydrocarbon surfactant K12 and xanthan gum exhibit a nonlinear synergistic effect in retarding foam drainage, while excessive addition is detrimental. Moreover, temperature exhibits a dual regulatory mechanism on foam drainage: in high viscosity system, increasing temperature always promotes foam drainage; in the low viscosity system, the effect of temperature rise on the foam drainage is first delayed and then accelerated, resulting in a non-monotonic change in the 25% drainage time. Based on the above rules, 25 groups of formulas were designed for fire extinguishing experiments, and the effectiveness of the formula design method based on drainage control was verified. For STAR-2157/2470, the optimal range of 25% drainage time was determined to be 5.9 ± 0.2 min, and two groups of AFFF formulas that met the national fire extinguishing standards were successfully screened.