Xiaoyang Yu,Ning Jiang,Xuyang Miao,Fan Li,Jiyun Wang,Ruowen Zong,Shouxiang Lu
The application of fluorocarbon surfactants in fire-fighting foam has been restricted due to their serious environmental hazards. Thus, it is necessary to develop the fluorine-free foam for fire-fighting and understand their characteristics from different perspectives compared with the fluorinated foam. The present study investigated foam stability, oil-film interaction, and fire extinguishing performance for fluorine-free and fluorinated foams. The results show that the adverse effect of oil on the stability of fluorinated foams is much less than that of fluorine-free foams. Besides, the trends in foam stability are not predicted by the entering, spreading, and bridging coefficients based on the measurement of surface and interfacial tensions. The differences in stability of fluorine-free and fluorinated foams are found to be consistent with the observation of oil-film interaction. Oil droplets destabilize the fluorine-free film by spreading over the film, whereas they tend to be rapidly expelled out of the fluorinated film in the form of oil lenses slightly affecting the film stability. Since the film is unstable in contact with oil, the fluorine-free foam cannot suppress the pool fire effectively at the expansion ratio of 6.8–7.2. By adjusting the foam expansion ratio, the fire extinction performance of the fluorine-free foam can be comparable to that of the fluorinated foam, and the burnback performance is significantly enhanced.
Youjie Sheng,Tiantian Wang,Yang Li,Li Ma,Qian Zhao,Baohu Li
The development of highly stable and environmentally friendly foams is of utmost urgency. This study systematically investigated the effects of temperature on the viscosity and viscoelasticity of fluorine-free foams stabilized by guar gum (GG), silicon, and hydrocarbon surfactants. The experiment investigated the surface properties and foaming ability of various hydrocarbon surfactants, and selected the excellent BS-12 and the silicone surfactant LS-408L for compound use. The research found that the viscosity of the LS-408L/BS-12 solution increased as the concentration of GG increased. Among them, when the concentration of GG was 0.2wt%, the foam exhibited excellent stability. The rheological tests demonstrated that both the LS-408L/BS-12/GG stabilized foam solution and the foam exhibited the non-Newtonian fluid characteristics of shear thinning. As the temperature rises, the viscosity and viscoelasticity of the solution and the foam continue to decrease. It is notable that when the temperature reaches 67 °C, the loss factor (tan δ) is much greater than 1, indicating that the foam exhibits a significant dominant viscous behavior. Moreover, when the temperature reached 80 °C, the foam drainage accelerated, and the drained liquid exhibited a dynamic elastic response structure under the effect of high temperature. This study provides key data support for the optimized design of fluorine-free foam materials and has guiding significance for their application in different temperature environments.
Yunpeng Yang,Lilong Nie,Yongkang Guo,Zhuoxuan Li,Sicheng Xu,Linlin Yi,Kaiyuan Li
To address the environmental risks posed by PFOS-containing fire extinguishing agents, the development of highly efficient and environmentally friendly fluorine-free foam extinguishing agents has become a forefront research area in the firefighting community. In this study, a novel foam extinguishing agent was prepared using the nonionic silicone surfactant SiCare2238 and the amphoteric hydrocarbon surfactant LAMC as core components, with hydrophilic nano-SiO₂ particles (NPs) introduced to construct a gas–liquid-solid three-phase fluorine-free foam system. By regulating the NP concentration, the interactions of NPs and surfactants and the resulting effects on the foam performance were investigated. The results indicate that when the NP concentration is < 1 wt%, the charge interactions between particles and surfactants weaken the interfacial adsorption, leading to accelerated drainage and coarsening, thereby reducing the foam stability. In contrast, when the NP concentration is ≥ 1 wt%, the particles form a dense network in the Plateau borders, blocking the Plateau channels, resulting in a 47.4 % reduction in drainage within 30 min and a 30 % decrease in coarsening rate, significantly enhancing the foam stability. Moreover, the fire extinguishing and burn-back experiments demonstrated that the SN-7# system with 5 wt% NPs achieved a 90 % flame control time of 17 s and an extinguishing time of 26 s, outperforming the commercial AFFF and the NP-free SN-0#. The addition of NPs significantly enhances fire suppression efficiency, as they interact with surfactants in foam films and Plateau borders to form aggregated network structures, effectively delaying the drainage and coarsening, thereby improving the foam’s thermal stability and burn-back resistance. The findings of this study provide theoretical guidance for the development and application of NPs in fluorine-free foam extinguishing agents.
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