Modulation of fluorocarbon surfactant diffusion with diethylene glycol butyl ether for improved foam characteristics and fire suppression

Abstract Analysis of aqueous solutions comprised of a fluorocarbon-betaine surfactant with and without diethylene glycol butyl ether (DGBE) have provided insight into the effect of DGBE on fire suppression and foam quality. Incorporation of DGBE decreased the Sauter mean bubble size and liquid drainage that resulted in faster foam spread, which lead to improved fire suppression performance at slow foam application rates. The DGBE effects were found to be relatively small at fast foam application rates. Dynamic surface tension characterization showed that diffusion of the surfactant was more rapid in the water-DGBE solvent system such that the air-liquid interface could have stabilized faster thus resulting in a smaller bubble size. The faster surfactant diffusion in the presence of DGBE is consistent with the measurements of larger micelle diffusion coefficients and smaller micelle sizes when DGBE is included with the fluorocarbon surfactant. Smaller observed micelle size provides evidence of the incorporation of DGBE into the fluorocarbon surfactant micelle within the palisade layer thus altering the micelle composition and size. Measurements of bubble size, dynamic surface tension and micelle size support altered fluorocarbon surfactant behavior in solution which resulted in the generation of a more stable foam capable of faster foam spread and fire suppression as a result of the presence of DGBE in solution.