| The modified urushiol-based composite resin has become an important direction for the development of natural organic polymer anti-corrosion coatings,due to its advantages of high crosslinking density and composite resin.The main application of graphene oxide for metal corrosion was adding graphene oxide or its hybrid materials as filler into the polymeric coatings due to its unique physical properties,chemical stability,thermal stability and excellent barrier properties to water molecules,oxygen and electrolytes in the air.Grapheme oxide is prone to agglomeration due to its large specific surface area and surface energy.Therefore,improving the dispersion stability and compatibility of graphene oxide?GO?in modified lacquer-based resin is a problem in the fields of academic and industrial of graphene and natural organic polymer anticorrosion.According to these problems,a novel modified urushiol-based polymer using urushiol as the base material and different types of modified graphene oxide were prepared by various processes,and modified graphene was combined with the above polymer to prepare a new composite coating.Meanwhile,the relationship between the structure and corrosion resistance mechanism of the composite coating were studied.The main research contents and conclusion of our study are as follows:1.Graphene oxide?GO?was modified by 3-methacryloxypropyltrimethoxy silane?MPS?to obtain modified graphene oxide?MGO?.MGO was dispersed in urushiol formaldehyde polymer by mechanical mixing and ultrasonic dispersion,and MGO/urushiol formaldehyde polymer?UFP?coatings with different MGO contents were fabricated.The microstructure,physico-mechanical properties and electrochemical properties of the MGO/UFP composite coatings were investigated.The results indicated that the hardness,adhesion and corrosion resistance of the MGO/UFP composite coating were obviously enhanced compared with the pure UFP coating.The hardness and the adhesion grade of the MGO/UFP composite coating with 3.5 wt.%MGO?GO,1.5 wt.%and MPS,2.0 wt.%?reached 6H and 2,respectively.Additionally,GO connected with MPS by chemical bond and the well-dispersed MGO in UFP could significantly enhance the anti-corrosion performance of the UFP coatings,which could result from bending the diffusion pathway of penetrant species in the UFP coating matrix.2.Multi-walled carbon nanotubes?MWCNTs?were uniformly dispersed in an urushiol formaldehyde polymer?UFP?by in-situ condensation polymerization reaction with an alkali catalyzer,and then modified graphene oxide/multi-walled carbon nanotubes/urushiol formaldehyde polymer?GO/MWCNTs/UFP?composites coatings were fabricated via solution blending.The microstructure,physico-mechanical properties and anti-corrosion properties of the GO/MWCNTs/UFP composite coating were studied.By optimizing the GO/MWCNTs content?0.5 wt.%GO/1.0 wt.%MWCNTs?,a significant improvement of the alkali resistance and physico-mechanical properties was realized.The morphology of the as-prepared UFP composite films was studied using scanning electron microscope?SEM?.The SEM demonstrated that the MWCNTs were well dissolved and covered by the GO.The hardness,adhesion,surface drying time and corrosion resistance of the GO/MWCNTs/UFP composite coating were obviously improved compared to the pure UFP.A relatively fast surface drying time of 30 min was reached compared to the pure UFP.The hardness and the adhesion grade of the GO/MWCNTs/UFP composite coating?0.5 wt.%GO/1.0 wt.%MWCNTs?reached the highest level of 6H and 1,respectively.It was investigated that when tinplate was coated with GO/MWCNTs/UFP composite,the corrosion rate decreased up to 1.62×10-55 mm/a and protection efficiency increased up to 99.70%.The resulting GO/MWCNTs/UFP films exhibit outstanding properties in electrochemical corrosion,alkali-resistance,hardness and adhesion,which provide a high potential for use in offshore steel structures applications.3.Composite coatings were fabricated based on a graphene oxide–oxide/urushiol formaldehyde polymer?GO–TiO2/UFP,GO–SiO2/UFP and GO–Y2O3/UFP?system with modifications,and demonstrated its effectiveness in corrosion protection of metal substrates.First,a GO–TiO2 composite was synthesized using titanium dioxide loading on GO via3-aminopropyltriethoxysilane?APTES?.The GO–Y2O3 composite was synthesized using the silanecouplingagents3-aminopropyltrimethoxysilane?APS?and3-methacryloxypropyltrimethoxy silane?MPS?.The GO–SiO2 composite was synthesized via an in-situ two-step sol-gel process utilizing 3-aminopropyltriethoxysilane?APTES?and tetraethylorthosilicate?TEOS?in an aqueous ethanol solution.The morphology and structure of the GO–oxide composites?GO–TiO2,GO–Y2O3 and GO–SiO2?was studied.Subsequently,GO–oxide was incorporated into UFP to investigate the composite's effectiveness in corrosion protection of metal substrates.Compared with GO–TiO2/UFP and GO–Y2O3/UFP,GO–SiO2/UFP showed superior alkali-resistance enhancing performance.Additionally,GO cross-linked with APTES–TiO2 via covalent bonds and the well-dispersed GO–TiO2 in UFP improved the electrochemical corrosion properties of the UFP coatings,most likely due to the obstruction of the diffusion pathways inside the UFP coating matrix,thus preventing the diffusion of penetrating species.4.The modified cellulose nanofibrils?APTES-CNF?were synthesized using silane coupling agent 3-aminopropyltriethoxysilane?APTES?,and then graphene oxide-cellulose nanofibrils?GO-CNF?suspension were prepared by high-intensity ultrasonic method,and the modified cellulose nanofibril aqueous suspension was added to the waterborne urushiol-based mixture?WU?.The water-based coating composite was applied to the glass plate and the tinplate,respectively,and the composite film were structurally characterized and tested for conventional physical and mechanical properties.The results indicated that the hardness,adhesion and corrosion resistance of the GO-CNF/WU composite coating were obviously enhanced compared with the WU coating.The hardness and the adhesion grade of the CNF/WU composite coating with 10 wt.%APTES-CNF reached 6H and 1,respectively.Additionally,GO connected with CNF by chemical bond and the well-dispersed GO-CNF in WU could significantly enhance the anti-corrosion performance of the WU coatings,which could result from bending the diffusion pathway of penetrant species in the WU coating matrix.5.The lacquer-based graphene oxide?MGO/UA?composite coating was prepared by UV curing.The curing time required was much shorter than that of thermal curing,only 120 s.The heat resistance of MGO/UA composite coating was improved.When the MGO content is1.5 wt.%,the hardness reaches 6H,and the adhesion is increased to grade 1.When the content of MGO is 2.0 wt.%,the film has excellent electrochemical corrosion performance;the salt resistance and acid resistance of MGO/UA composite film are outstanding,the alkali resistance is improved,and the corrosion resistance is related to the MGO content.The MGO/UA samples with MGO content of 1.0 wt.%were the best to enhance corrosion resistance. |
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