Preparation And Properties Of Titanate Functionalized Graphene And Its Composite Anticorrosive Coatings

Graphene is a nanoscale functional carbon material similar to natural graphite.There are functional groups exist on the carbon layer,resulting in very poor water and oil wettability,as well as the low reactivity with other substances.Moreover,graphene tends to aggregate together due to the Van der Waals force between layer and layer.Therefore,it is necessary to modify graphene nanosheet by introducing some specific functional groups to improve the dispersibility,endow it with novel properties,and thereby extend its application field.In this paper,titanate functionalized graphene were synthesized by using titanate coupling agent and applied to waterborne acrylate-alkyd resin(WAAR).The properties of homemade graphene oxide,graphene and functionalized graphene were compared systematically.The modifier dosage,reaction time and reaction temperature were determined.The structure and morphology of graphene oxide,graphene and functionalized graphene were characterized by X-ray photoelectron spectroscopy(XPS)and field emission scanning electron microscopy(SEM)and other testing methods.And the thermal properties and water resistance of functional graphene/waterborne acrylate-alkyd resin(FRGO/WAAR)compositeswerestudied.Inaddition,the corresponding corrosion resistance was studied.The main work and conclusions in this thesis are as follows:(1)Graphene oxide were prepared through the improved Hummers method and the functionalized graphene(FRGO)were synthesized by using hydrazine hydrate as reducing agent and the titanate coupling agent TM-200S or 311W as modifier.The effects of titanate coupling agent dosage,reaction temperature,reaction time on the properties of modified graphene were studied.The optimum preparation scheme of TM-200S modified graphene was that the mass ratio of graphene oxide(GO)to TM-200S was 1:7,the reaction temperature was 80?and the reaction time was 8 h.For 311W modified graphene,the mass ratio of311W to GO was 5:1,the reaction temperature was 90?,and the reaction time was 7 h.(2)The dispersity of titanate functionalized graphene in solvent was studied and the results shown that dispersibility was improved after modified with titanate coupling agent.The dispersibility of TM-200S modified graphene's(T200S-RGO)in ethyl acetate,ethanol and water was obviously improved,and there were no precipitation after graphene was dispersed in acetone,ethyl acetate,N,N-dimethyl formamide(DMF)and N-methyl pyrrolidone(NMP)more than 20 days,but there have slight precipitation in the water.The dispersibility of 311W modified graphene's(311W-RGO)in acetone and ethyl acetate was also evidently improved,and there was no precipitation after dispersed functionalized graphene in acetone,ethyl acetate,ethanol,water,DMF and NMP after more than 20 days.The conductivity of T200S-RGO and 311W-RGO increased from 421 S/m to 627 S/m and 868 S/m,respectively.The results of X-ray photoelectron spectroscopy(XPS)test showed that there exist P 2p and Ti 2p peaks in these two functionalized graphene's XPS spectrograms,and both the C/O ratio and the intensity of C=C peak increased.Meanwhile,surface morphology of functionalized graphene was characterized by transmission electron microscop(TEM)and scanning electron microscopy(SEM)and the results shown that both T200S-RGO and 311W-RGO presented two-dimensional thin layer structure.Thedecompositiontemperatureofcarbonlayerin T200S-RGO and 311W-RGO increased by 40?and 70?respectively compared with GO,and the weight loss rate of heat treatment decreased obviously.(3)FRGO/WAAR composite emulsion was prepared by using FRGO as nanofiller and waterborne acrylate-alkyd resin(WAAR)as matrix.The effect of different FRGO content to the composite material was discussed.Emulsion stability test showed that with the increase of the FRGO content,the emulsion stability increased and then decreased,the stability of the emulsion reached optimum when the FRGO content was 0.5%and there was no obvious floating and sinking phenomenon.The heat resistance was studied by thermogravimetric test,compared with the film of pure waterborne acrylate-alkyd resin(WAAR),the thermal decomposition temperature of the FRGO/WAAR-0.5%film increased by 48?.And it can be seen from the DTG that the narrow peak area of FRGO/WAAR-0.5%indicates that the material has good compatibility and the peak value of DTG shifts to a higher temperature and this phenomenon proved that the heat resistance of WAAR is improved after FRGO was introduced.The water resistance of FRGO/WAAR latex film was studied by water absorption test.With the increase of FRGO content,the water absorption of FRGO/WAAR-0.5%decreased to 8.23%,which shows optimal water resistance.SEM image of fractured surface of FRGO/WAAR films with different contents showed that the addition of FRGO reduced the flatness of the fracture surface,and the composite of FRGO/WAAR-0.5%have the flattest fracture surface,As the content of FRGO increased continuously,the film have rougher fracture surface and more curly folds layer structure.The corrosion resistance of FRGO/WAAR composites was studied by electrochemical tests.With the increase of FRGO content,the resistance value of FRGO/WAAR coating first increased and then decreased.When?(FRGO)=0.5%,the coating had the highest impedance(1.19E-8?·cm~2),highest anti-corrosion efficiency(99.96%),the corrosion voltage(-0.351 V)and the lowest corrosion current density(5.268E-9A/cm~2).At the same time,after soaking in 3.5%Na Cl solution for 120 h,the low frequency impedance decreased by only one order of magnitude and still showed a high impedance at low frequency.