| Graphene is an ideal filler for anticorrosive coatings due to its excellent sheet barrier,mechanical and electrical conductivity properties.However,in the actual application process,it is difficult to disperse in the coating and form agglomerates due to the large specific surface area of graphene,which not only causes stress concentration of the cured coating to reduce its mechanical properties,but also the corrosion resistance of the coating will be greatly weakened or even worse.Dry graphene powder is difficult to redisperse in solvents.Generally speaking,according to the thinner coating used,it is divided into water-based and oil-based.Water-based coatings are environmentally friendly.However,due to the short development time and lack of industry standards,many properties are not as good as oil-based coatings,therefore,oil-based coatings are still the main for defense,marine and heavy industry infrastructure.However,graphene is difficult to disperse and has a low dispersion concentration in organic solvents such as xylene and ethyl acetate.Therefore,graphene cannot be directly added to oily coatings for application,How to prepare high concentration oily redispersible graphene powder has become one of the key scientific technologies.In this thesis,a re-oil dispersible graphene powder is first prepared,and then it is dissolved in an organic solvent to obtain a graphene oily dispersion or slurry,which is used as filler in coatings.In order to improve the dispersibility of graphene in oily solvents,polymer microspheres such as polystyrene were first supported on the surface of graphene oxide?GO?to overcome the van der Waals force between graphene sheets in water environment,and then reduced and dried to obtain modified reduced graphene oxide powder,which has both the characteristics of graphene and dispersibility in oily solvents.However,which polymer is used to modify graphene oxide is very important,both the solubility of the polymer in the coating solvent and the compatibility or micro-morphology after blending between the polymer used and the coating resin matrix must be considered.This thesis integrates the above factors,and the research content is as follows:?1?Polyvinylpyrrolidone?PVP,K30?was first added to the graphene oxide aqueous solution as a connecting agent between the polystyrene?PS??polymethyl methacrylate?PMMA?microspheres and the graphene oxide sheet.Then,polystyrene microspheres were loaded on the surface of graphene oxide by in-situ polymerization to overcome the van der Waals force between the layers,and reduced by hydrazine hydrate,dried to obtain modified graphene powder.And when the mass ratio of GO to PVP is less than 1:1.5,the loading effect of polymer microspheres is the best,and powders with different loadings are made according to the different amounts of monomers such as styrene,scanning electron microscopy?SEM?,pulling Mann,Fourier infrared spectroscopy?FT-IR?and X-ray diffraction?XRD?were used to analyze the micro-morphology,chemical composition and crystal structure of the composite powder.In addition,combined with first-principles?DFT?calculations,it is shown that the interaction between PVP,PS and GO is physical adsorption.?2?The modified graphene powder was dissolved in different organic solvents,and the dispersion was characterized by optical photographs and peak intensity of Ultraviolet–visible spectroscopy under different organic solvents and concentrations,when the polystyrene loading is higher than 10%,the modified powder can be well dispersed in xylene,the dispersion concentration is high to form a slurry,and the redispersion effect is good after dilution.when the polystyrene loading is below 10%,the dispersion effect becomes worse;graphene modified by polymethyl methacrylate can only be well dispersed in acetone but insoluble in xylene.Acetone is volatile and therefore unsuitable as a thinner for oily coatings.?3?After graphene modified by the PS microsphere dispersion was added to the fluorocarbon resin coating,due to compatibility problems between the dissolved PS and the fluorocarbon resin,new Polymer blend morphology was occurred due to the PS chain microscopically self-assembled.The blended morphology was characterized by scanning electron microscopy and mesoscopic simulation.The results showed that after adding the dissolved PS to the fluorocarbon resin,the PS molecular chains agglomerated to form micron-sized PS balls due to compatibility.The mechanical properties of the layer have been improved to some extent.?4?Investigate the optimal amount of modified graphene dispersion in fluorocarbon resin coatings.By testing the micro-defect morphology and salt spray resistance of the coating,the performance is best when the amount is 1.5%;impact resistance through the coating Performance and adhesion test.When the addition amount is 1%,the coating performance is the best.According to the Tafel and EIS tests of the coating,when the addition amount is1.5%,the Ecoor of the coating is-0.306V,The minimum is 7.954×10-12Acm-2.From the above data,it is concluded that when the added amount of the modified powder PS-PVP@rGO is 1.5%,it is the optimal addition amount of the coating. |
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