Flame-retardant Application Of Zirconium-based And Molybdenum-based Metal-organic Framework Hybrid Materials In Epoxy Resin

Epoxy resin(EP)is an important thermosetting resin,which can be divided into glycidyl ether epoxy resin,glycidyl lipid epoxy resin,glycidyl amine epoxy resin,aliphatic epoxy resin,etc.species.Because of its excellent adhesion,electrical insulation and chemical resistance,it is widely used in production and life.However,the poor fire resistance of EP and the emission large amounts of smoke and toxic gases in the combustion limit its application in the fields of architecture and aviation.Therefore,flame retardants are often added to EP products to enhance the flame retardancy and smoke suppression properties.Traditional inorganic flame retardants,such as magnesium hydroxide and aluminum hydroxide,are used in many polymers as typical inorganic flame retardants.Although magnesium hydroxide and aluminum hydroxide have certain functions of reducing heat release and smoke elimination,generally,large content(?50%)is needed to achieve desired flame-retardant effect in single hydroxide flame retardant,which makes the fluidity of polymer in the processing process worse,and worsens the processability and mechanical properties of materials.In recent years,exploring new flame retardant has become an important research focus.Metal-organic Frameworks(MOFs)are organic-inorganic materials with permanent adjustable pores formed by self-assembly of metal ions(or clusters)and organic ligands through coordination bonds.MOFs have developed rapidly in the past ten years and have shown exciting prospects in many fields,such as:gas adsorption and separation,catalysis,loaded drugs and electrode materials.At the same time,the porous structure,catalytic properties,modifiable properties,and abundant organic ligands of MOFs materials show great flame-retardant application value.Therefore,the application of MOFs in the field of flame retardant is worthy of in-depth research,in order to expand its application range and open new ideas for the research direction of flame retardants.In this paper,we selected zirconium-based MOF(UiO-66-NH₂)with excellent stability and post-modification properties.After rapid in-situ growth on Graphene nanoplatelets(Gn Ps),it was grafted with hexachlorocyclotriphosphazene(HCCP),regarded as G-U-H;Then,it was added to EP to prepare composite materials to study its flame-retardant properties and mechanical properties;finally,the flame retardant was analyzed.In the second system,an ionic liquid(1-butyl-3-methylimidazolium tetrafluoroborate,[BMIM]BF₄)modified graphene oxide(GO)loaded molybdenum-based MOF(Mo-MOF)hybrid material was prepared and added to EP to study its effect on the flame retardant properties and mechanical properties of EP composites,and finally,the the flame retardant mechanism of the flame retardant was analyzed.The details are as follows:Part I:UiO-66-NH₂ on ball milled graphene nanoplatelets and hybridizes with hexachlorocyclotriphosphazene towards fire safety of epoxy resin.In this section,first use wet ball milling to peel off the expanded graphite(EG)using ball mill to prepare ball milled graphene for use,and then rapidly grow UiO-66-NH₂ particles on the graphene sheet by microwave hydrothermal method,and finally through MOF active amino group(-NH₂),Zr-OH sites and-OH of the Gn Ps are grafted with HCCP.X-ray diffraction(XRD),atomic force microscopy(AFM),scanning electron microscopy(SEM),fourier transform infrared spectroscopy(FT-IR),Raman spectra,X-ray photoelectron spectroscopy(XPS)and thermogravimetric analysis(TGA-DTG)were used to characterize the morphology,element composition,crystal structure,grafting reaction and thermal properties of graphene nanoplatelets and G-U-H.Through the analysis of the characterization results,it is found that the UiO-66-NH₂ particles have regular octahedral structure,and the size is about 400 nm,which can uniformly grow on the Gn Ps.At the same time,HCCP was successfully grafted with-NH₂?Zr-OH of UiO-66-NH₂ and-OH of Gn Ps.Then,the flame retardancy of EP composites was tested,the limiting oxygen index increased from 23.6%of the pure EP to 27.3%of EP-3(3 wt%addition of flame retardant);cone calorimetry test results showed that the peak heat release rate and peak smoke production rate of EP-3 were reduced by 33.20%and 20.79%respectively compared with pure EP.In addition,the maximum CO production rate and total CO release decreased by 25.0%and 12.23%,respectively.Finally,combined with the characterization of carbon residue(XPS,XRD,FT-IR,SEM,Raman spectroscopy),the flame-retardant mechanism is proposed.Part II:[BMIM]BF₄ modified GO supported MO-MOF hybrid material and its epoxy flame retardant researchIn this chapter,GO was firstly prepared by Hummer's method,and then Mo-MOF was grown on the surface of GO,which was noted as GM;finally,[BMIM]BF₄ was wrapped on the outer surface of GM by solid-phase milling,which was noted as GMB.The flame retardants were analyzed by inductively coupled plasma-emission spectroscopy,XRD,TEM,SEM,FT-IR and TG for the crystalline shape,morphology,elemental content,functional groups,and thermal properties of the flame retardants were analyzed by inductively coupled plasma emission spectroscopy,XRD,TEM,SEM,FT-IR and TGA-DTG.Then the composite flame retardant materials were prepared by adding Mo-MOF,GM and GMB to the epoxy resin at a mass ratio of 3 wt%,and the flame retardant properties of the composites were tested by ultimate oxygen index,vertical combustion test and cone calorimetry test,and the test results showed that the peak heat release rate and peak smoke release of the EP composites decreased by 52.10%and 40.12%,respectively.The flame retardant mechanism of the flame retardant was proposed by combining the characterization analysis of the residual carbon(XPS,XRD,FT-IR,SEM-EDS,Raman spectroscopy)and the analysis of the gas phase products by thermogravimetric-infrared coupling.Finally,the mechanical properties of the composites were tested and the tensile sections were analyzed using SEM.