Technical Research On Improving The Fluidity Of Ultrafine Dry Powder Fire Extinguishing Agent

Ultrafine powder extinguishing agent has various advantages of high fire-extinguishing efficiency,wide range of application,non-toxic effect to human bodies and domestic animals,and it has always been one of the best substitutes for Halon fire extinguishing agent.However,the ultrafine particles of fire extinguishing agent are extremely easy to agglomerate,which result to the decrease of its fluidity and fire extinguishing performance.Meanwhile,the poor oleophobic property of particles makes it impossible to put out oil fires.To solve these problems,sodium bicarbonate ultrafine dry powder fire extinguishing agent was used to carry out experimental research,and ulterfine dry powder fire extinguishing agent was prepared by the process of grinding-modification-grinding in this paper.Firstly,talc powder,synthetic zeolite,mica,activated clay and nano calcium carbonate were adopted as additives of sodium bicarbonate,and the effect of additive dosage on material fluidity were studied respectively at the same time.After the recipe of fire extinguishing agent was determined,the ultrafine dry powder fire extinguishing agent was prepared by omni-directional planetary ball mill.The D₉₀particle size of obtained fire extinguishing agent was 20.8?m,and the fluidity value was 0.353,which were both better than that of sodium bicarbonate obtained by direct grinding without any additives.It indicated that the additives could effectively improve the fluidity of ultrafine dry powder fire extinguishing agent.Then the fire extinguishing agent obtained above was modified with silicone oil by dry method.After modifying under optimal parameters determined by orthogonal test and range analysis,the particle size of obtained fire extinguishing agent was significantly decreased and the fluidity was significantly improved.Its D₉₀particle size was only 9.2?m,and the fluidity value was only 0.184.What's more,it also possessed excellent hydrophobic property without the phenomenon of agglomeration.The only shortcoming was weak oleophobic property,the fire extinguishing agent particles would rapidly sink when they contact the oil surface.Therefore,two environment-friendly fluorinated acrylate copolymers(FP)were also adopted to modify the surface of ultrafine dry powder fire extinguishing agent in this paper.After modifying by wet method and grinding process,the fire extinguishing agent modified by fluorinated acrylate copolymer 2(FP2)possessed better performance.Its D₉₀particle size was 7.4?m,and the fluidity value was 0.233.Meanwhile,the fluorine content on particle surface was 37.4%,the contact angle of deionized water was 117°and that of aviation kerosene reached 120.5°,which indicated that both its hydrophobic and oleophobic properties were excellent,the particles could completely float on the surface of two liquids without the phenomenon of agglomeration.Ultimately,the re-modification process was also adopted in this paper,FP2 was used to modify the silicone oil modifying superfine dry powder fire extinguishing agent.The D₉₀particle size of obtained fire extinguishing agent was 7.5?m and the fluidity value was 0.279.Its contact angle of deionized water was 107°and that of aviation kerosene was only 95.5°.The properties were not as good as the fire extinguishing agent prepared by using silicone oil or FP2 alone.