The physicochemical and fire extinguishing performance of aqueous film‐forming foams based on a class of short‐chain fluorinated surfactants

Abstract

Aqueous film‐forming foams (AFFFs) are an important for fire extinguishing, and their key ingredient is fluorinated surfactant. In recent years, traditional long‐chain fluorinated surfactants have been banned by most countries because of their persistence, bio‐accumulation and toxicity. Therefore, increased attention has been paid to the research and development of short‐chain fluorinated surfactants. As is well known, the introduction of hydrophilic or hydrophobic groups in a surfactant affects its surface activity, and therefore, the fire extinguishing performance of AFFFs. In this work, a series of short‐chain fluorosurfactant‐based AFFFs with different hydrophobic chain lengths were prepared. The physicochemical performance of mixed systems (fluorinated surfactant plus sodium hexanesulfonate), including surface activity, spreading ability, foam expansion, drainage time, and the fire extinguishing and burn‐back performance of AFFFs were studied. The results show that the critical micelle concentration (CMC) and the surface tension (γCMC) at the CMC of mixed systems at 25°C are lower than 7.68 mmol/L and 16.51 mN/m, respectively. For mixed systems, the average spreading rate is more than 1.09 cm/s, the foam expansion is over 7.1, and the drainage time is greater than 3.28 min. The fire extinguishing time of AFFFs on fuels is less than 51 s while the burn‐back time is more than 15.18 min. The results imply a potential application prospect of the short‐chain fluorinated surfactants in AFFFs.

Effect of low pressure on the properties of short‐chain fluorocarbon surfactants and their application in aqueous film‐forming foam extinguishing agent

“…So, it is important to study the foaming and spreading properties of fluorocarbon surfactant. In addition, previous work has shown that the combination of fluorocarbon and hydrocarbon surfactants (sodium hexanesulfonate, SHS) can produce synergistic effects, which is conducive to improving its foaming and spreading properties (He et al, 2019; Jia et al, 2019; Zhu et al, 2022). Therefore, the foaming and spreading properties of single system (FC‐4) and mixed system (the equimolar binary system FC‐4/SHS) are studied in this work.…”

“…In order to further explore the application effect of fluorocarbon surfactants in firefighting, AFFF fire extinguishing agent based on FC-4 mixed system was configured in this work to verify its fire extinguishing performance under different pressures. AFFF configuration method is based on previous work (Zhu et al, 2022), and the results of fire extinguishing experiment are shown in Table 7. We can see that the fire extinguishing time decreases with the decrease of pressure, and the burn-back time is the opposite, indicating that the fire extinguishing speed is faster and the burn resistance is longer under low pressure.…”

Formulation and performance of aqueous film-forming foam fire extinguishing agent composed of a short-chain perfluorinated heterocyclic surfactant as the key component

“…These surfactants have not yet been classi ed under international law, but may be suitable substitutes for longchain uorosurfactants (Peshoria et al 2020). Zhu et al synthesized a class of short-chain uorinated cationic surfactants, and prepared three types of AFFF solutions (AFFFs-eth, AFFFs-pro, and AFFFs-but), with AFFFs-but being the most effective, consistent with China National Standard 15308 − 2006, ICAO, and NFPA requirements (Zhu et al 2022). Additionally, a per uoro branched short-chain uorocarbon cationic surfactant with high surface activity was produced and utilized to form three AFFF formulations (F-1, F-2, and F-3), with the F-3 formulation outperforming typical AFFF formulations (Yang et al 2022).…”