Influence Of Silica Nanoparticles On Foam Stability Of Firefi Ghting Foams

Aqueous film-forming foam(AFFF)is a type of firefighting foams used to extinguish flammable liquid fires.Its high efficiency in fire extinguishment is achieved by a water film layer and a foam layer formed on the surface of liquid fuel upon AFFF application.However,the core component of AFFF,the long-chain fluorocarbon surfactants,have proved to have serious environmental problems and its application has been restricted severely.It is an urgent task to developing a new generation of environmentally friendly firefighting foams suitable for flammable liquid fires.In the present study,nanoparticle-stabilized foams are focused in order to develop the environmentally friendly firefighting foams.The effect of nanoparticles on the foam stability of the firefighting foams are studied systematically.First,the hydrophilic silica nanoparticles and the core components of firefighting foams,foaming agent and foam stabilizer,are chosen for preparing the mixed dispersions of nanoparticles and the core components.Influence of nanoparticles on surface activity,viscosity and electrical conductivity of the mixed dispersions was studied deeply.The results show that the addition of silica nanoparticles leads to the increase in surface activity and viscosity of the foaming agent system,and the decrease in the conductivity,while the increase of the concentration of silica nanoparticles leads to the increase in the surface activity,viscosity and conductivity of the mixed dispersions of foaming agent and foam stabilizerSecondly,the effect of silica nanoparticles on the foam properties of the core component of firefighting foams was studied.The results show that silica nanoparticles can improve the foaming ability and the foam stability of the foaming agent.When silica nanoparticles coexist with xanthan gum or carboxymethyl cellulose,the foaming ability of the foaming agent is reduced,and the foam stability is significantly improved.However,the mixture of polyacrylamide and silica nanoparticles resulted in decease in the foaming ability and foam stability.Finally,fluorocarbon surfactant,hydrocarbon surfactant,xanthan gum,antifreeze,cosolvent,and other components were selected for preparing AFFF concentrates.The effect of silica nanoparticles on the stability of the prepared AFFF was studied.The results show that silica nanoparticles can effectively delay the drainage and coarsening of AFFF,significantly improving the foam stability.The silica nanoparticles aggregated and formed a stable network structure at foam bubble films and Plateau borders,effectively delaying foam drainage and coarsening,and hence enhance foam stability.The results obtained from this study can provide theoretical support for the application of silica nanoparticles in environmentally friendly firefighting foams.