Study On The Preparation And Flame Retardancy Of Functionalized Graphene Modified Mineral Materials

In this paper,graphene oxide(GO)was prepared by Hummers method,and ZnO,Fe₃O₄ and TiO₂ were used to modify GO respectively to obtain three functionalized graphene oxide ZnO/GO,Fe₃O₄/GO and SO₄^2-/TiO₂-GO.X-ray diffraction(XRD),Fourier Transform infrared spectroscopy(FTIR),transmission electron microscopy(TEM)and thermogravimetric analysis(TG)tests showed that three kinds of functionalized go with good thermal stability were successfully prepared.Finally,three functionalized GO synergies with traditional flame retardants were applied to flame retardant polyurethane foam(RPUF)and epoxy resin(EP)respectively to obtain ZnO/GO/EG/MRP/RPUF,Fe₃O₄-GO/APP/EP and SO₄^2-/TiO₂-GO/EG/MRP/EP flame retardant composites.The flame retardancy and flame retardancy mechanism of flame retardant composites were analyzed by limiting oxygen index(LOI),vertical combustion(UL-94),thermogravimetric analysis(TG),cone calorimetric analysis(CCT)and scanning electron microscopy(SEM).The results showed that:1.Synergistic flame retardant RPUF based on GO or ZnO/GO combined with expandable graphite/microencapsulated red phosphorus(EG/MRP):The characteristic absorption peak of ZnO/GO at 460 cm^-1 and the diffraction peak of ZnO crystal surface were observed,and the ZnO/GO nanomaterials were successfully prepared.Meanwhile,the thermal stability and dispersion of ZnO/GO were improved.EG/MRP combined with ZnO/GO has a significant flame retardant effect on RPUF,the limiting oxygen index is 28.8,the combustion grade reaches V-0,and the heat emission of the composite decreases by 11.33%,the smoke emission by 7.64%,and the CO₂ emission by 6.75%.These results indicate that ZnO loaded on the surface of GO and used for flame retardant RPUF can improve the catalytic char formation and physical barrier effect of GO,and ZnO/GO synergistic with EG/MRP flame retardant EP has good performance of smoke suppression,heat insulation and gas release inhibition.2.Synergistic flame retardant EP composite based on GO or Fe₃O₄/GO compound ammonium polyphosphate(APP):Fe₃O₄/GO showed characteristic absorption peaks of C-N,CH₂ and Fe-O bonds.In addition,XRD test of Fe₃O₄/GO showed crystal plane diffraction peaks of Fe₃O₄ and TEM images showed that there were black clusters on the Fe₃O₄/GO lamellers,which indicated that Fe₃O₄@SiO₂-NH₂ had been successfully loaded on the GO surface.The magnetic-controlled Fe₃O₄/GO synergistic effect of APP flame retardant epoxy resin is good,LOI reaches 32.0,which belongs to non-combustible level,and vertical combustion level reaches V-0 level.Meanwhile,mechanical properties and thermal stability are significantly improved.The PHRR of EP-5 and EP-4 decreased to 9.35and 18.66 k W/m²,and THR decreased by 0.12 MJ/m² and 4.62 MJ/m²,respectively.The PSRP and TSP values of EP-5 were 17.31 m²s^-1 and 5755.93 m² m^-2,respectively.Compared with EP-4,Fe₃O₄/GO decreased by 25.55%and 28.06%,respectively,and the release of CO and CO₂ also decreased significantly,indicating that Fe₃O₄/GO not only plays a catalytic role in carbon formation and physical barrier,but also can better block heat exchange and flue gas release.The maximum FPI value of EP-5 is0.6750,indicating the lowest fire risk.3.SO₄^2-/TiO₂-GO composite EG/MRP synergistic flame retardant EP composite:The characteristic frequencies of S-O bond and O-S-O bond appear in SO₄^2-/TiO₂-GO,indicating that the surface of GO is loaded with SO₄^2-and has the characteristic diffraction peak of TiO₂,and it is a mixture of TiO₂ rutile and anatase,which means the functionalized graphene is successfully prepared.SO₄^2-/TiO₂-GO lamellae stacking was not obvious and agglomeration was not easy,and the thermal stability was significantly higher.SO₄^2-/TiO₂-GO synergistic effect of MRP/EG EP resin is good,and the limit oxygen index reaches 33.8,which belongs to non-combustible grade,and the vertical combustion grade reaches V-0 grade.Compared with EP-3,PHRR and THR of EP-4 decreased by 96.06 k W/m² and 10.87 MJ/m²,PSPR and TSP decreased by 18.27%and 7.75%,respectively,and the release of CO and CO₂decreased significantly,indicating that the modification of SO₄^2-/TiO₂ improved the catalytic carbon formation and physical barrier effect of GO.The carbon layer formed by EP composite combustion is more compact and continuous,and the heat exchange and flue gas exchange are reduced.In conclusion,ZnO/GO,Fe₃O₄/GO and SO₄^2-/TiO₂-GO have good thermal stability and dispersion,and have synergistic effects on EG/MRP/RPUF,APP/EP and EG/MRP/EP flame retardant systems,respectively.ZnO/GO,Fe₃O₄/GO and SO₄^2-/TiO₂-GO not only improve the flame retardancy,mechanical properties and thermal stability of thermosetting polymers,but also inhibit smoke,heat insulation and reduce the release of gas through good thermal stability and continuous dense expansion carbon layer structure formed in the combustion process.