Thermal stability of highly stable foams stabilized by nanoparticles and surfactants

Foams stabilized by nanoparticles (NPs) and surfactants have a great research potential in the development of environment-friendly firefighting foams. In the present study, foam dispersions, consisting of hydrophilic SiO 2 NPs, a hydrocarbon surfactant (CAD-40), and a fluorocarbon surfactant (FS-50), were prepared to investigate the effect of NPs on the thermal stability of firefighting foams. The interactions between NPs and surfactants and foaming ability of the mixed dispersions were investigated. Foam decay, drainage, and coarsening under different thermal radiation intensities were systematically investigated. Results indicated that as the NP concentration was increased, the viscosity of the foam dispersions increased rapidly, the conductivity and foaming ability decreased, and the surface activity decreased initially and then increased. Foam volume decay, drainage, and coarsening under different temperatures were delayed by the NPs. As the concentration of NPs increased, the effect became more obvious. This study could provide theoretical guidance for the application of NPs in firefighting foams.