| Epoxy resin(EP)is a kind of important thermosetting polymer material,which is often used in coatings,adhesives,electrical insulating materials,composite materials and other fields for its excellent chemical corrosion resistance,mechanical properties,electrical insulation,and thermal conductivity.However,the flammability of epoxy resin and the inherent brittleness of epoxy resin limit its application.Therefore,it is indispensable to improve its heat resistance and fire retardant performance,in order to meet the application needs in various fields.Epoxy intumescent fire retardant coatings for steel structure have characteristics of high weather resistance,high corrosion resistance and can effectively prevent the building from collapsing and prolong the escape time.As a conquence,it is of great significance for fireproof of steel structures and offshore oil platforms.The high loading requirements of traditional intumescent flame retardants have resulted in the disadvantages of high density,lack of toughness,poor mechanical properties and bonding properties,and difficulty in processing.Therefore,it is very important to develop a new type of synergistic agent for intumescent flame retardant system to realize high efficiency fireproof.In addition,in order to expand the application of epoxy resin in other fields,it is urgent to develop an effective flame retardant to improve the flame retardancy and mechanical properties of epoxy resin.In this paper,we have designed and synthesized a kind of multi-element flame retardant modified graphene oxide and discussed.the application of graphite-based flame retardant in epoxy resin fire retardant material.The specific contents are as follows:1.Graphene oxide(GO)was synthesized by the improved Hummers method.Afterwards,maleic anhydride was grafted to GO.And then P-H on 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide(DOPO)and epoxy on 1,3,5-triglycidyl isocyanurate(TGIC)reacted with carbon-carbon double bond and carboxyl groups,respectively,to synthesis functionalized graphene oxide(GOMT).The resultant functionalized GO called GOMT were characterized by Fourier transform infrared spectroscopy(FT-IR),X-ray photoelectron spectra(XPS),X-ray diffraction(XRD)and Raman spectroscopy,atomic force microscope(AFM),transmission electron microscopy(TEM),scanning electron microscope(SEM),energy dispersive X-ray spectroscopy(EDX),thermogravimetric analysis(TGA).Furthermore,GOMT was homogeneous dispersion and incorporated into diglycidyl ether of bisphenol A(DGEBA)to prepare nanocomposites.The effects of GOMT on the curing reactivity,mechanical,thermal and flame retardant properties the nanocomposites were investigated systematically.It can be concluded that functionalized graphene oxide(GOMT)was synthesized successfully,and it had good compatibility with epoxy resin.TGA shows that GOMT has better thermal stability,and the char of GOMT under 1100℃ increases when compared to that of graphene oxide.Compared to pure EP,the char residue of GOMT/EP nanocomposites increased and its LOI value increased to 28.1,while the UL-94 rating was V-1 with the addition of 3 phr GOMT.With the addition of 1 phr GOMT,Tg increases to 165.6℃.Moreover,the storage modulus elevated from 1.26 GPa for pure EP to the ultimate value of 1.50 GPa with a 19.0%increase when 3 phr GOMT.Furthermore,the addition of 5 phr GOMT increases the elastic modulus and flexural strength of epoxy composite at room temperature by 17.9%and 26.7%,respectively.These data indicated that GOMT not only obviously enhanced the flame retardancy,but also improved the mechanical properties and thermal stability of epoxy resins.2.An bi-component graphene/epoxy ultra thin intumescent fire retardant coating for steel structure is studied.A component is mainly composed of epoxy resin(E-51)as film-forming material,and ammonium polyphosphate,pentaerythritol,melamine as expansion flame retardant system.Titanium dioxide,expandable graphite(EG),and graphene nanoplatelets(GM)is used as synergistic flame retardant.B component mainly consist of polyamide 140 as a curing agent.The structure of expanded carbon layer,fire resistance of intumescent coating and fireproof mechanism were studied by vertical combustion method,thermogravimetric analysis(TGA),scanning electron microscopy(SEM),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS)and infrared spectroscopy(FTIR).The epoxy resin fireproof coating prepared by mixing A and B components expanded after burning,and titanium dioxide formed titanium pyrophosphate at high temperature,which improved the fireproof performance.The synergistic flame retardant effect of EG was better than that of GM under the same conditions.The expansion of carbon layer was a "P-N-C" network structure,which mainly contained P,N,C,O elements.In conclusion,fire performance and comprehensive physicochemical properties of the coating is the best when the proportion of epoxy resin is 24%,and the ratio of JLS-APP,MEL and PER is 14:8:5,and the total content of them is 55%-60%in the fireproof coating.The fire retardant coatings expansion under fire,and the expanded carbon layer shows a honeycomb-like structure.XRD data show that white ceramic-like porous the material layer formed on the surface of char residues is titanium pyrophosphate(TiP2O7),which can enhance strength of the carbon layer and act as insulation and anti-oxidative effect,thereby improving the performance of fireproof coating.SEM shows that expandable graphite formed vermicular graphite after combustion,interspersed into char residues,reinforcing the strength of carbon layer and working as synergistic flame retardant.and the flame retardant effect of two kinds of graphene nanosheets is compared under the same conditions.Results show that the fireproof performance of graphene nanosheets was slightly poorer than expanded graphite.The results of TGA test showed that the char of the flame retardant coating was greatly improved.The XPS and FTIR studies found that the carbon layer is composed of P,N,C,O and other elements to form a "P-N-C" network structure. |
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