Experimental Study on Effect of Foam Stabilizers on Aqueous Film-Forming Foam

Abstract

Aqueous film-forming foam (AFFF) is widely used in both military and civilian applications as an effective method to suppress flammable liquid fires. The present study focuses on identifying the contribution of different foam stabilizers to performance of AFFF. Carboxymethylcellulose, xanthan gum, triethanolamine and lauryl alcohol, are chosen as foam stabilizers of AFFF to synthetize AFFF formulation concentrates, and their mass concentration in AFFF is varied in the range of 0–2%, 0–0.4%, 0–4%, and 0–3%, respectively. Subsequently, the properties of AFFF aqueous solutions, including surface tension, interfacial tension, film-forming property, viscosity and foaming ability are measured. In particular, a new apparatus is established to evaluate the effect of foam stabilizers on foam drainage and foam spreading property. Finally, fire extinguishing tests and burn-back tests of AFFF containing different foam stabilizers are performed with a circular pan, 0.25 m2 in surface area. The results indicated that film-forming property and foam spreading property are decreased by the addition of the foam stabilizers. Foam stability of AFFF can be enhanced by the addition of carboxymethylcellulose and xanthan gum but reduced by the addition of triethanolamine and lauryl alcohol. The AFFF containing 0.4% xanthan gum shows the optimal foam stability, but the AFFF containing 0.3% xanthan gum shows the optimal fire extinguishing performance. This indicates that fire extinguishing efficiency is affected by multiple factors. In selecting foam stabilizers we need to be trading off factors such as film-forming property, foam stability and foam spreading property.