| Carbon-based nanomaterials are considered as a leader in material field due to its outstanding physical properties.The two-dimensional lamellar structure of graphene oxide can fully block the penetration of corrosive media into the substrate.The high aspect ratio of carbon nanotubes can be used as a nanofiber to enhance the toughness of the coating and makes the coating denser,resulting in a significant increase in the corrosion resistance of the coating.The high-strength mechanical properties of graphene oxide and carbon nanotubes can increase the wear resistance and impact resistance of the coating,and their chemical stability can improve the chemical resistance of the coating.However,nanomaterials usually have high specific surface energy,strong van der Waals force between molecules,makes its hard to disperse in the coating,this factor seriously restricts the application of nanomaterials in coatings.In order to make nanomaterials have good dispersion in coatings and compatibility with coatings,nanomaterials need to be effectively modified to solve this problems.This paper adopts the following three ways to modify nanomaterials:(1)There are many oxygen-containing functional groups on the surface of graphene oxide and carboxyl multi-walled carbon nano tubes.The acylation of the nanomaterials was carried out with thionyl chloride,followed by reaction with 3-aminophenoxyphthalonitrile to obtain the cyano-functional nanomaterials GO-CN and CNTs-CN.Then the surface polarity of the nanomaterial was enhanced and the dispersibility in the organic solvent was improved.Thus,the compatibility between the filler and the epoxy resin was improved,the interaction between the filler and the resin was enhanced,so the corrosion resistance of the epoxy resin can be improved.(2)One-pot synthesis of graphene oxide:First,dopamine was used to modify the graphene oxide to enhance the adhesion property of graphene oxide,and at the same time,a large number of amino functional groups were grafted on the surface.Then,the coupling agent KH560 was added into the solvent to obtain the product GO-PDA-GPS to acquire a large amount of epoxy groups on the surface.One-pot synthesis was performed on carboxyl multi-walled carbon nanotubes:The carbon nano tubes was first modified with dopamine to enhance the adhesion of carbon nanotubes,and give a large number of amino functional groups on the surface.Then the coupling agent KH550 was added to the solvent to obtain CNTs-PDA-APS.The two different nanomaterials then participate in the curing reaction during the curing of the epoxy coating to form a three-dimensional cross-linked space structure,so that the composite coating has high strength,denseness and barrier properties,thereby enhancing the corrosion resistance of the coating.(3)The use of hyperbranched polyarylamide for the modification of graphene oxide and carboxyl multi-walled carbon nanotubes results in a more open terminal structure and abundant functional groups.The reactivity of graphene oxide and carbon nanotubes are enhanced by hydrogen bonds and covalent bonds,and hyperbranched polymers have a higher solubility,improve dispersibility and compatibility in epoxy resin from these aspects.The FT-IR,TGA,XPS and other methods were used to characterize the structure of the nanomaterials modified by three different methods to confirm the successful modification of nanofillers.A composite coating was prepared from the filler and the resin.The cross-section SEM was used to observe the dispersion of the filler in the resin.Finally,the electrochemical curve was used to measure the polarization curve and the AC impedance of the composite coating,and the addition of the filler to the coating was discussed.The effect of corrosion performance shows that the synergistically enhanced epoxy composite coating of graphene oxide and carbon nanotubes has superior corrosion resistance compared to pure epoxy coatings and other types of composite coatings. |
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