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Preparing fluorocarbon surfactant for aqueous film-forming foam is a complex process. Overcoming steric hindrance when introducing imidazolium to the fluorocarbon chain is a key challenge. In this significant work, we proposed a simple one-step route to prepare imidazolium-contained fluorocarbon surfactant under mild conditions. The FT-IR, 1H NMR, 13C NMR, MS, and TG technologies characterized the imidazolium-contained fluorocarbon surfactant by analyzing functional groups, molecular weight, and thermal stability. An equimolar mixture of imidazolium-contained fluorocarbon surfactant and C6H13NaO3S demonstrated high surface activity, enabling the foam to spread effectively on commercial fuels. The spreading coefficient of foam on n-cyclohexane met the US Military Specification. Coordinatively, the foam drained in time to maintain the stability and completeness of the aqueous layer, with a moderate 25% drainage time of 317 s and a proper foam expansion ratio of 10.5. In extinguishing experiments, the imidazolium-contained fluorocarbon surfactant/C6H13NaO3 mixture extinguished test fires in 65 s, suggesting an essential potential in the aqueous film-forming foam formula. [ABSTRACT FROM AUTHOR]

Surface properties of three fluorocarbon surfactants with different carbon chain lengths were studied at low pressures of 94.6, 74.1 and 61.0 kPa, respectively. The results showed that the saturation adsorption capacity and the critical micelle concentration (CMC) decreased, while the average molecular area (AS) and the surface tension at CMC (γCMC) of fluorocarbon surfactants increased with decreasing pressure. The surface tension (γ) decreased with the decrease of pressure when the concentration of fluorocarbon surfactants was low. However, γ tended to be stable and increased with the drop of pressure when the concentration of surfactants was close or reach to CMC. In addition, the foaming and spreading performance of fluorocarbon surfactants decrease with the decrease of pressure, and the combination of fluorocarbon and hydrocarbon surfactants is beneficial to the improvement of performance (mixed systems: foam expansion E>6, 25% drainage time t25%>241 s, 1/2 defoaming time t1/2>851 s, spreading amount Vs>223 μL, spreading time ts<2 s). Further fire extinguishing experiment found that the influence of low pressure environment on fuel combustion characteristics is the key factor to determine fire extinguishing performance, while the influence of aqueous film‐forming foam (AFFF) performance is small. And AFFF based on the environmental‐friendly surfactant C4F9SO2NH(CH2)2N+(CH3)2CH2BrCH2OH (FC‐4) is an effective fire extinguishing agent under low pressure. [ABSTRACT FROM AUTHOR]

A new method for studying the two-dimensional spreading properties and sealing characteristics of surfactant solution on oil surface was provided. The actual spreading situation of the C4-Br/oil systems in axisymmetric geometry was observed directly using HD camera for the first time and the results showed that the aqueous film expanded outwards in a circle with the guiding device as the center. Meanwhile, the relation between spreading radius and time was investigated and evaluated using the model for surface-tension-viscous regime. The root-mean-square deviation (RMSD) values obtained from the correlation for all of the systems we studied below 1.64, indicating a good agreement between the experimental and theoretical values. The results of sealing experiments showed that the aqueous film could absolutely seal the oil surface for 27–65 s and the sealing effect would be lost after 216–742 s for different systems. The stronger the volatility was, the shorter the sealing time was. Additionally, the volume percentage of oil vapor with film was always lower than that without film even when the evaporation was saturated. These findings were of great significance to guide the preparation of efficient AFFF. [ABSTRACT FROM AUTHOR]

A novel short fluorocarbon chain cationic surfactant has been synthesized to reduce the bioaccumulation of traditional fluorocarbon surfactants and maintain excellent surface properties simultaneously. The structure, surface activity, and micelle formation of surfactants have been investigated by surface tension, conductivity, dynamic light scattering, steady‐state fluorescence, Fourier transform infrared spectroscopy, and Nuclear magnetic resonance. The novel surfactant (yield more than 81%) exhibited good surface activity, the critical micelle concentration and surface tension were below 2.35 mmol L−1 and 20.54 mN m−1 in the range of temperature from 288 to 303 K, respectively. The surface tension decreased to 17.45 mN m−1 with an increase in temperature. The thermodynamic parameters (ΔGm0, ΔHm0 and ΔSm0) of micellization for surfactants were evaluated, which implying the micellization process was contributed primarily by the entropy driving. In addition, the aggregation behavior of surfactants was also studied in detail, which demonstrated a small micelle aggregation number of 9.40 and large size distribution of 164–342 nm. [ABSTRACT FROM AUTHOR]

Aqueous film-forming foam (AFFF) is a very important extinguishing agent for hydrocarbon fuel fires. The spreading performance of AFFF is one of the key factors to decide its extinguishing efficiency. There are many parameters that affect the spreading performance of AFFF, but few studies have been done on its spreading mechanism. A method for studying the spreading performance of surfactant solution on different oil surfaces was provided in this work. Additionally, the kinetics of C4-Br/CH 3 (CH 2) 5 NaO 3 S, C6-Br/CH 3 (CH 2) 5 NaO 3 S and C8-Br/CH 3 (CH 2) 5 NaO 3 S equimolar system spread on the surfaces of cyclohexane, n -heptane, aviation kerosene, solvent naphtha and diesel oil 0# were investigated. Meanwhile, the relationship between spreading length and time at 25℃ were obtained and the experimental data were evaluated using the model for surface-tension-viscous regime. The root-mean-square deviation (RMSD) values obtained from the correlation using surface-tension-viscous regime model for all of the systems we studied below 3.41, indicating a good agreement between the experimental and theoretical values. It meant that the surface-tension-viscous regime model could be used to predict the process of the aqueous film formed by surfactant solution spread on the hydrocarbon oils. Furthermore, the theoretical spreading rate (R) and average spreading rate (R ¯) from 0 to 50 s of C4-Br/oil, C6-Br/oil and C8-Br/oil systems were also investigated. The results showed that the R decreased with increasing time and the rate of decline slowed down gradually. The R ¯ increased with the increase of fluorocarbon chains. In particular, the effect of fuel kinematic viscosity on spreading rate was also very obvious. The greater the kinematic viscosity of fuel, the smaller influence of the surfactant tail length on spreading rate. [ABSTRACT FROM AUTHOR]

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