Investigation on thermal stability of highly stable fluorine-free foam co-stabilized by silica nanoparticles and multi-component surfactants

Abstract

Nanoparticles (NPs) have shown promising applications in developing the novel environmental-friendly firefighting foams. Hydrophilic silica NPs, siloxane surfactant (CoatOsil-77), and hydrocarbon surfactant (BS-12) were used to prepare mixed foam dispersions. The adsorption between surfactant molecules and NPs, and foamability of the mixed dispersions were analyzed. Thermal stability of foam was evaluated by using foam drainage, coarsening, and volume decay under thermal radiation. The strengthening mechanism of NPs on thermal stability of foam was analyzed. Results indicate that the intense interaction exists between NPs and surfactants. The presence of NPs with a concentration below 1 wt% leads to the deterioration of foam stability by accelerating foam drainage and coarsening, while a concentration of NPs above 1.5 wt% enhances foam stability. The foam coarsening, drainage, and foam volume decay were obviously delayed by NPs under thermal radiation. This research can give theoretical guidance for NP application in invention of fluorine-free firefighting foams.