Study On Synthesis And Properties Of Phosphorus-containing Boron Salen-based Schiff Base Flame Retardant

In this paper,a novel type of phosphorus-containing schiff base multifunctional organic-inorganic hybrid core-shell flame retardant(Salen-PZN-Cu@Ni-Mof)was designed,and a new type of boron-containing flame retardant Boron-containing Schiff base flame retardant dihydro(E)-2-((2,4-dihydroxybenzylidene)amino)ethyl(B-HIBD)was prepared through molecular design.Besides,boron-based flame retardant B-HIBD was phosphatized to synthesize flame retardant DOMB and HCBD to explore its flame retardant performance and mechanism of action on polymer materials offering the theoretical evidence for the preparation of more efficient and environmentally friendly new flame retardants.Infrared spectroscopy(FT-IR),scanning electron microscopy(SEM),transmission electron microscopy(TEM),nuclear magnetic proton spectroscopy(1H NMR),thermogravimetric(TGA)were Used to evaluate and analyze the structure,morphology,thermal stability of flame retardants.X-ray photoelectron diffraction spectroscopy(XPS)and Raman spectroscopy(RS)were characterized to analyze carbon residue structure.Cone calorimeter(CC)was used to evaluate the combustion performance of the material,and the tensile strength test was used to explore the effect of each additive on EP The influence of mechanical properties of materials.The research results show that when the additive amount is 3wt%,the introduction of Salen-PZN-Cu@Ni-Mof significantly improves the thermal stability and fire safety of EP composites,which is attributed to the phosphazene structure,metal ion catalysis into charcoal,and the strong adsorption performance of the porous Mof adsorption material.In addition,the It was found through tensile strength test that Ni-Mof can effectively improve the compatibility between the flame retardant and the EP matrix.With the same amount of addition,the total release of PHRR,THR,SPR,TSP and CO of the B-HIBD/EP composite material was reduced by 58.2%,18.3%,65.9%,51.2%,28.4%,illustrating that the introduction of B-HIBD significantly improved the thermal stability of EP composites.In addition to the catalysis of the schiff base structure contained in B-HIBD itself,borate also promotes the formation of carbon layers at high temperatures,enhancing flame retardant effect of the condensed phase and inhibiting combustion of EP to a certain extent.In addition,through the tensile strength test,we found that the additive B-HIBD can reduce the brittleness of the material to a certain extent,and the boron element can maintain the original mechanical properties of the material.Both the flame retardants DOMB and HCBD can significantly improve the fire safety of epoxy resin composites.That’s because of the strong catalysis of characteristic group C=N and the flame retardant effect of element B itself.In addition,DOPO group in the DOMB flame retardant and the phosphazene group in the HCBD played a flame-retardant effect in the condensed phase and the gas phase,respectively.Among them,DOMB can endow EP materials with higher stability,smoke suppression,more continuous and dense carbon layer structure due to the existence of cyclic side phosphorus group O=P-O.Besides,it is found through tensile experiments that the additive DOMB had a greater impact on the mechanical properties of EP materials.