Suppression of Fuel Evaporation by Aqueous Films of Fluorochemical Surfactant Solutions

摘要

Solutions of aqueous fluorochemical surfactants were placed on the surface of liquid hydrocarbons and hydrocarbon fuels to study the film-forming ability of the surfactant solutions. Spreading coefficients were calculated for a number of surfactant solution/hydrocarbon liquid pairs and correlations made with visual observations of film formation. In a majority of cases, film formation could be predicted from the spreading coefficient of the surfactant solution on the hydrocarbon substrate. Both pure fluorochemical surfactants and commercially available fire fighting concentrates were used to prepare the aqueous solutions. The hydrocarbon liquids and fuels included n-heptane, isooctane, cyclohexane, jet fuels JP-4 and JP-5, motor fuel (gasoline), and stove and lighting naphtha. The effect of temperature on surface and interfacial tension measurements was also studied. In general, the surface tensions of the hydrocarbon liquids and the interfacial tensions between the surfactant and hydrocarbon liquid pairs decreased at a rate of approximately 0.07 to 0.12 dynes per cm per deg C temperature rise. The surface tensions of the surfactant solutions were found to decrease approximately 0.05 to 0.06 dynes per cm per deg C rise. (Author)