| With the widespread application of carbon fiber/epoxy resin composites in the rail transit industry and the increase in flame retardant requirements,the advantages of phosphorus-containing epoxy resin as a resin matrix have gradually become prominent,but its smoke generation characteristics and smoke suppression research have been become a hot spot of attention.Aiming at the problems of low smoke suppression efficiency and poor dispersion of additive smoke suppressants,this paper proposed a new idea for the design of a synergistic smoke suppression system combining physical modification of smoke suppressants and chemical doping,based on phosphorus-containing epoxy resin and ammonium octamolybdate(AOM),hollow glass microspheres(HGM),blends of AOM and HGM(AOM+HGM)and coated smoke suppressor microspheres(AOM@HGM),prepared a series of smoke suppression phosphorus-containing epoxy resin composites.The smoke suppression effect of the composites was evaluated,the thermal degradation process of the composites was studied,the smoke suppression mechanism from condensed phase and gas phase were proposed,and the smoke suppression mechanism model of the composites was constructed.(1)AOM smoke suppressant with concentrated distribution of particle size and suitable crystal structure was prepared by the reaction of molybdenum oxide and ammonium molybdate;the surface roughness and chemically active of the microspheres were improved by the surface hydroxylation of HGM and the grafting treatment of the coupling agent,and the coated smoke suppressant microspheres(AOM@HGM)loaded with ammonium octamolybdate on the surface were prepared by in-situ synthesis.The ammonium octamolybdate on the surface of the microspheres was petal-like and arranged densely.(2)Four smoke suppression PEP composites were prepared by AOM,HGM,AOM+HGM and AOM@HGM smoke suppressants,respectively.The morphology of cross-section,mechanical and flame retardant properties of the smoke suppression phosphorus-containing epoxy resin composites were analyzed,and the composite materials were evaluated.Compared with EPO,the smoke suppression performance of the smoke suppressant modified composites have been improved:Ds(4)and VOF(4)of the EP/AOM@HGM composites were lower than other composites.The smoke generation rate(SPR)and total smoke generation(TSP)curves of EP/AOM@HGM composites were significantly lower than that of unmodified PEP.(3)The thermal weight loss behavior,carbon residue morphology,raman analysis and element distribution of the smoke suppression phosphorus containing epoxy resin composites were compared respectively,and the mechanism models of smoke suppression of four smoke suppression systems in the condensed phase were proposed:Compared with EPO,EP/HGM and EP/AOM composites,AOM and HGM in EP/AOM+HGM and EP/AOM@HGM composites exert a barrier effect together,and their char residue morphology integrity and graphitization degree both improved significantly;The gas phase decomposition products of EP/AOM+HGM and EP/AOM@HGM composites were compared and the smoke suppression mechanism model in the gas phase was proposed:during the combustion process,the reduction of phosphorus and oxygen free radicals leads to the weakening of the quenching effect,which helps the full combustion of the decomposition products in the gas phase and reduces the production of smoke. |
