Fluorinated and fluorine-free firefighting foams spread on heptane surface

Abstract

The application of fluorinated firefighting foam has been restricted due to its serious environmental hazard. Thus, new fluorine-free firefighting foam formulations must be urgently developed. In this work, fluorinated and fluorine-free firefighting foams are synthesized. The spreading of the two foams on the surface of liquid fuel is achieved by using a circle stainless steel tray. Variation in the instantaneous spreading area of the foams versus time is analyzed. In addition, the effect of foam flow rate and expansion ratio (ER) on foam spreading is studied. Results indicate that an aqueous film on the heptane surface is observed during fluorinated foam spreading but not during fluorine-free foam spreading. At the same foam flow rate and ER, fluorinated foam shows faster spreading than fluorine-free foam. The foam spreading rate (FSR) increases with the increasing foam flow rate and decreases with the increasing ER. The high surface tension and great viscosity of fluorine-free foam solution are significant factors resulting in its slow spreading. Therefore, fluorine-free foam can spread on the heptane surface as fast as fluorinated foam by increasing the foam flow rate and lowering the ER.