Study On Synthesis And Application Of Environmentally Friendly Fluorocarbon Surfactants

Aqueous film-forming foam（AFFF）has many advantages,such as fast fire extinguishing speed,high efficiency,strong anti-reburning ability,long storage period,and suitable for large-scale fires,oil fires in gaps and dead corners.It is an ideal substitute for halon fire extinguishing agent.AFFF is the main fire extinguishing agent designated by the International Civil Aviation Organization（ICAO）for aircraft and aviation fuel fires.However,perfluorooctane sulphonate（PFOS）,the core component of traditional AFFF,is a toxic organic pollutant that is difficult to degrade and is listed as a persistent organic pollutants（POPs）by the United Nations Environment Program（EPA）.The fire protection industry must upgrade and transform the industry as soon as possible to find alternatives to PFOS.In this thesis,a series of non-toxic non-polluting and non-PFOS surfactants were synthesized through reasonable molecular design.The surfactants with low surface tension,good foaming and spreading properties were selected for the preparation of foam fire extinguishing agents,to explored the environmental aviation fire foam extinguishing agent formula.In this thesis,perfluorohexylsulfonyl fluoride(C₆F₁₃SO₂F),as the lipophilic group,reacted with N,N’-dimethyl-1,3-propanediamine by quaternary ammonium saltation first.Then a series of cationic surfactants based on perfluorohexylsulfonyl fluoride were synthesized by the reaction of the intermediate products with bromhydrin/bromoic acid/ethyl bromoacetate.The three products were identified by infrared spectrum,mass spectrometry,and nuclear magnetic resonance.The synthetic product is determined to be the target product of the thesis design.According to previous research results,the key performance parameters that determine the AFFF fire extinguishing performance are surface tension,micelle concentration（cmc）value,foaming multiple,drainage time,and spreading performance.By testing the above performance parameters,it was found that the lowest critical micelle concentration（cmc）of the three surfactants is FC-6-D1,which is 0.5 mM.The lowest surface tensionγ_cmc,is 16.02 mN/m.The foaming multiple can reach 8 times.25%drainage time is79 s.Overall physical and chemical properties are better than the other two products.It is a surfactant with the potential to prepare AFFF.Because the production cost of fluorocarbon surfactants is high and the performance of a single surfactant is not outstanding,the appropriate hydrocarbon surfactant can usually be used to combine with fluorocarbon surfactant.In this way,the amount of fluorocarbon surfactant can be reduced and its physicochemical properties can be further improved.In this thesis,three series of nine kinds of hydrocarbon surfactants,sulfonate,carboxylate,and perfluorocarboxylate,were used to mix with FC-6-D1.By testing its cmc,spreading speed,foaming factor,25%drainage time,the fluorocarbon-hydrocarbon compounding system with excellent performance was selected.The results show that FC-6-D1 has the best compounding effect with sodium hexanesulfonate,with the fastest spreading speed at low concentrations,foaming multiple of 12.3 times,and 25%drainage time 140 s.The synergistic effect of the composite system is obvious.The initial formulation of AFFF can be determined by adding appropriate foaming agents,foam stabilizers,and other auxiliary additives to the compounding system.Aqueous solution of the formula can quickly spread on the oil surface,with a foaming factor of 12.7 and 25%drainage time of 3.82 min.Using the formula proposed in the thesis,the fire extinguishing experiments were carried out according to the“test methods specified in the national standard foam extinguishing agent”"GB15308-2006"for portable fire extinguishers and"small tests for quality control of foam performance and fire performance".It was found that the hand-held fire extinguisher had a fire extinguishing time of 15s.The fire extinguishing performance was better than that of a commercial brand.The fire extinguishing time is 50s and the anti-burning time is 15min,which meets the requirements of Class IA standard.