Flame Retardancy Of Epoxy Resin/MOFs Composites

Epoxy resin(EP)has been widely used in many fields because of its outstanding properties.However,epoxy resin is easy to burn.It releases a large amount of heat and toxic smoke during combustion,which threatens the safety of people’s life and property and greatly limits the application of epoxy resin.Therefore,how to improve the fire safety performance of epoxy resin has become an urgent problem to be solved.This paper summarized the research progress of the flame-retardant epoxy resin composites at home and abroad,based on the the transition metal organic framework(MOFs)with high efficiency catalytic carbonization and smoke suppression effect.A series of novel modified MOFs were synthesized.The effect of these MOFs on the flame retardancy of epoxy resin was systematically studied,and the flame retardant mechanism was discussed.Iron 2-methylimidazole MOF(Fe-MOF),cobalt 2-methylimidazole MOF(Co-MOF)and nickel 2-methylimidazole MOF(Ni-MOF)were synthesized by solvothermal method,respectatively.These transition metal organic framework materials were added to EP with the same content,and their combustion performance were tested.The results indicated that Fe-MOF can improve the flame retardancy of EP better than Co-MOF and Ni-MOF.Then Fe-MOF was modified by melamine polyphosphate(MPP)to form MPP-Fe-MOF,which acted as flame retardant and was incorporated into EP.The results demonstrated that MPP-Fe-MOF could improve the thermal stability of EP.The combustion tests indicated that 1 wt%MPP-Fe-MOF could dramatically increase the limiting oxygen index(LOI)values of EP and EP/1 MPP-Fe-MOF passed the vertical burning test(UL-94)V1 rating.In addition,the thermal stability and flame retardancy of EP/MPP-Fe-MOF were better than those of EP/M-Fe-MOF and EP/Fe-MOF at the same amount of addition.The improvement of thermal stability and flame retardancy performance of EP/MPP-Fe-MOF was mainly due to the synergistic flame retardancy of MPP and Fe-MOF.The iron-based oxalate-phosphate-amine metal organic framework(OPA-MOF)rich in phosphorus and nitrogen was synthesized by hydrothermal method and incorporated into EP.The results indicated that OPA-MOF had superior catalytic charring performance in the condensed phase and improved the thermal stability of EP at high temperature.The char residue of EP/8 OPA-MOF composite at 700 ~oC was 28.5 wt%.In addition,OPA-MOF could reduce the PHRR and THR values of EP to a certain extent,and improved the flame retardancy of EP.The improvement of the thermal stability and flame retardancy performance of EP/OPA-MOF was attributed to the high thermal stability and excellent catalytic carbonization of OPA-MOF itself.This system solves the problem of low residual carbon content,but the addition amount of the flame retardant is too high to affect other properties of EP.Iron 2-methylimidazole MOF(Fe-MOF)was modified by sulfonyl diphenol polyphosphazene derivative(PZS)via an one-pot precipitation method to obtain PZS-Fe-MOF hybrid.Then PZS-Fe-MOF was added to the EP matrix to obtain epoxy composites.The results indicated that PZS-Fe-MOF could significantly increase the char residues at high temperature,thus improving the thermal stability of EP at high temperature.The char residue of EP/2 PZS-Fe-MOF composite at 700 ~oC was 32.4 wt%.In addition,PZS-Fe-MOF could obviously improve the flame retardancy of EP:1 wt%PZS-Fe-MOF could make the composite pass the vertical burning test(UL-94)V1 rating;3 wt%PZS-Fe-MOF could significantly reduce the PHRR,THR,PSPR and TSP values of EP.The improvement of thermal stability,flame retardancy and smoke suppression performance of EP/PZS-Fe-MOF was mainly due to the synergistic flame retardancy of PZS and Fe-MOF.This system not only solves the problem of low flame retardancy with high addition amount,but also increases the char residues of EP at high temperature,thus obviously improving the flame retardancy and smoke suppression properties of EP.