Preparation And Properties Of Isocyanate Functionalized Graphene/Alkyd Anticorrosive Coatings

Graphene is a carbon nanometer two-dimensional material with stable chemical properties.Due to the van der Waals force between layers,it is easy to agglomerate and difficult to disperse in solvents or matrices.It is of great significance to modify graphene,improve its dispersion,endow the material with excellent properties and expand its application range.In this paper,isocyanate functionalized graphene was prepared by modifying the surface of graphene with isophorone diisocyanate as a modifier.Modified graphene was applied to alkyd resin to prepare composite anticorrosive coating by solution blending.The optimum modifier dosage,reaction temperature and reaction time for the preparation of functionalized graphene were determined,and graphene oxide,graphene and functionalized graphene were characterized by X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),and their surface morphologies were analyzed by high resolution field emission scanning electron microscopy(SEM)and transmission electron microscopy(TEM).The mechanical properties,heat resistance and water resistance of alkyd resin composites were studied.The graphene composite anticorrosive coating was also characterized.The specific work is as follows:(1)The graphene oxide was prepared by the modified Hummers method,and the graphene oxide was modified and reduced by isophorone diisocyanate(IPDI)and hydrazine hydrate.The effects of IPDI dosage,reaction temperature and reaction time on modified graphene were discussed.The optimum conditions for preparing modified graphene were determined.the dosage ratio of GO and IPDI was 1:8,the reaction temperature was 80°C,and the reaction time was 8h.(2)The dispersion of IPDI modified graphene(IMG)in different solvents was studied.The results showed that IMG dispersed well in NMP,DMF and DGBE,and there was no delamination within 80 days.However,the dispersionin acetone,ethanol,ethyl acetate and water was poor,and delamination occurred in the fastest 5 days.After IPDI modification,the hydrophilicity of graphene was worse and the lipophilicity increased.This is because the isocyanate group is lipophilic,which increases the lipophilicity of modified graphene.The X-ray photoelectron spectrum shows that the N1 s peak appeared in the XPS spectrum of IMG;The percentage of N atoms is 4.95%.SEM analysis found that the surface of the modified graphene showed a layered wrinkle structure;the IMG showed a thin layer of yarn by TEM;the decomposition of IMG was found to be roughly divided into three stages by TGA,and The thermal stability of graphene after modification is good.(3)IMG/AR composite solution was prepared by IPDI modified graphene(IMG)as nanofiller and oily alkyd resin(AR)as matrix.The effects of different IMG content on the properties of the composite were discussed.The results showed that the stability of IMG in the composite solution decreases with the prolongation of time.With the increase of IMG content,the stability of IMG in the composite solution first increases and then weakens.When the amount of IMG is 0.5%,IMG has the best dispersion stability in solution,which is due to the uniform dispersion of IMG in alkyd resin;compared with pure AR,when the weight loss rate is 5%,the thermal decomposition temperature of the IMG dosage is 0.5% is increased by 25°C.It was found that the water absorption of the film first decreased and then increased with the change of IMG content.When the amount of IMG is 0.5%,the composite has better compatibility,the water absorption rate is 5%,and the contact angle is 86?;When the content of IMG is 0.5%,the tensile strength of the composite is the largest and the elongation at break is the smallest.SEM observation showed that the pure AR film showed a flat fracture surface,IMG changed the flatness of the fracture surface.When the IMG dosage was 0.5%,IMG was dispersed evenly in AR,but when the IMG dosage was further increased,a large number of particles were found,and the flatness of the fracture surface was reduced.AFM observation showed that when the amount of IMG was 0.5%,the surface roughness Ra of the film was reduced to 1.032,and the surface of the film was the smoothest.The results showed that when the IMG content is 0.5%,the IMG is uniformly dispersed in the alkyd resin matrix,which improves the properties ofthe composites.(4)IPDI-modified graphene(IMG)is used as an anti-corrosion filler,mixed with oily alkyd resin(AR)by solution blending,and various coating additives(such as dispersant,defoamer,wetting agent)are added,leveling agent and flash rust agent),high speed dispersion under high speed dispersing machine,IMG/AR anti-corrosion coating was prepared.The effects of different IMG contents on the properties of anticorrosive coatings were investigated.The results showed that when 0.5% IMG is added,the hardness of the coating reaches 4H,the adhesion level is 1 and the impact resistance reaches 90 Kg.cm.The mechanical properties were good.Compared to pure AR coatings,IMG-based anti-corrosion coatings exhibit higher impedance.As the amount of IMG changes continuously,the anti-corrosion performance of the coating also changes continuously.When the amount of IMG was added is 0.5%,the corrosion potential of the coating is the highest,and the corrosion current density of the metal is the lowest.The coating has the best anti-corrosion performance;the anti-corrosion coating with IMG added has better salt spray resistance than the coating without IMG;When placed in a salt sprayer for 480 h,the coating with 0.5% IMG added had a smaller corrosion area relative to the other coatings.The above results showed that when the amount of IMG is 0.5%,the IMG is uniformly dispersed in the alkyd resin matrix,effectively blocking the entry of corrosive media and improves the corrosion resistance of the coating.