Tuning stability, rheology, and fire-extinguishing performance of advanced firefighting foam material by inorganic nanoparticle flame retardants.

ABSTRACT

HYPOTHESIS: Nanoparticle-stabilized foams are extremely stable, and flame retardant inorganic nanoparticles should be able to add sealing capacity of firefighting foams on flammable liquid fuels, and hence enhance fire extinguishment performance on liquid fuel fire. In practice, how do flame retardant nanoparticles resist the destructive effect of oil molecules on foam and tune foam properties? EXPERIMENTS We have prepared a nanoparticle-enhanced foam comprising of hydrocarbon surfactant, short-chain fluorocarbon surfactant, and nanoparticles. The interactions among nanoparticles and surfactant molecules were characterized by using dynamic surface tension and conductivity. Stability, rheology, and oil resistivity on liquid fuel of the nanoparticle-enhanced foam were evaluated systematically. Fire suppression effectiveness of the foams was verified based on a standard experiment. FINDINGS: Foam stability and oil resistivity were enhanced due to self-assembled network structures formed by jammed aggregates composed by nanoparticles and surfactants in Plateau borders and bubble films, providing structural recoverability and enhanced viscoelasticity within foam. Foams containing nano-SiO2, nano-CaCO3, nano-Al(OH)3, and nano-Mg(OH)2 show difference in fire extinguishment due to different ability to enhance foam properties. Foam containing nano-Al(OH)3 shows the strongest adaptation and could shorten fire extinguishing time by 2 times and prolong burn-back time by 2.3 times compared with commercial product.