Design Of The Flame Retardants Of Ammonium Polyphosphate Coated With Metal-organic Framework And Their Performances

In this paper,three different metal-organic frameworks(MOFs)were used to coat and modify ammonium polyphosphate(APP)to prepare MOFs@APP flame retardants.MOFs@APP was added into epoxy resin(EP)to prepare flame-retardant epoxy resin composite material.The influence of MOFs@APP on epoxy resin composites were evaluated through mechanical performance,thermal stability,and flame retardant performance tests.ZIF-8@APP was prepared by in situ growth of the zeolite imidazole metal-organic framework ZIF-8 on the surface of APP using the co-precipitation method.ZIF-8@APP was added to the epoxy resin prepolymer,and cured to prepare flame-retardant ZIF-8@APP/EP composite material(EAZ).The results showed that when 5 wt%ZIF-8@APP was added,the limiting oxygen index of the EAZ-5 reached 28.3%and the vertical combustion test(UL-94)passed the V-1 level.The mechanical properties of the material were also improved.The total smoke production of EAZ-5 was 21.16 m~2,which was 62.0%lower than that of EA-5.The solvothermal method was used to load HKUST-1 on the surface of APP to prepare HKUST-1@APP,and HKUST-1@APP was mixed with epoxy resin prepolymer to prepare flame-retardant HKUST-1@APP/EP composite material(EAC).When adding 5 wt%HKUST-1@APP,the tensile strength of EAC-5 was 55.38 Mpa,which was 42.9%higher than that of EA-5.HKUST-1@APP also improved the flame retardant and smoke suppression properties of composite materials.The limiting oxygen index was 27.5%,and the vertical combustion test(UL-94)passed the V-1 level.HKUST-1@APP could also improve the carbon layer produced when epoxy resin burned,making the carbon layer more continuous and graphitized.The MOF-74(Ni)@APP was prepared by solvothermal method.The MOF-74(Ni)@APP was added to epoxy resin to obtain MOF-74(Ni)@APP/EP composite material(EAN).When the MOF-74(Ni)@APP was 5 wt%,the tensile strength of EAN-5 was increased to 56.52 Mpa.The SEM and Raman test of the residual char indicated that MOF-74(Ni)@APP colud effectively improve the structure of the EAN-5 expanded carbon layer and generate more continuous and graphitized carbon layer.Therefore,The limiting oxygen index of EAN-5reached 28.0%,and the UL-94 test level also passed the V-1 level.