Modification Of Graphene Oxide And Its Application In Waterborne Epoxy Anticorrosion Coatings

Owing to high thermal stability,excellent mechanical properties and outstanding barrier property,GO nanosheets can act as a suitable nanofiller to improve the anti-corrosion performance and other properties of polymer coating.However,GO tends to severely reunite in the coating matrix and its expected reinforced performances can not be well achieved.In order to resolve this issue,it is necessary to modify GO nanosheets to become compatible with polymers.In this thesis,the small organic molecules were used to modify GO via a green chemical method.Then the modified nanomaterials were incorporated into water-borne epoxy coating to fabricate nanocomposite coatings,and the effect and mechanism of the modified nanomaterials in anti-corrosion coating were investigated through a series of characterizations.The specific work includes the following two aspects:(1)The polyetheramine D230 molecule with double amines was used to modify GO nanosheets.Results obtained from Fourier transform infrared(FTIR)spectroscopy,X-ray diffraction(XRD)and Raman spectroscopy confirmed that D230 molecules were decorated onto GO surface.Then D230-GO nanofillers were added into WEP coatings,and the nanocomposite coating was applied on the surface of mild steel substrate.The SEM images demonstrated that D230-GO nanosheets could be well-dispersed in the WEP2060 coating with the help of curing agent D230(as the dispersant of D230-GO).The effect of D230-GO and GO nanosheets on the anti-corrosion property of the WEP₂₀₆₀coating was studied by electrochemical impedance spectroscopy(EIS).Results revealled that D230-GO/WEP₂₀₆₀coating had poorer anti-corrosion performance with respect to the pure WEP₂₀₆₀coating and GO/WEP₂₀₆₀coating.The result was caused by the ill-effect of uncrosslinked curing agent D230 and defects of GO introduced during the modified process.(2)A natural amino acid with double amines(Lysine)was used to modify GO.Results obtained from FTIR spectroscopy,Raman spectroscopy,X-ray photoelectron spectroscopy(XPS)and XRD spectroscopy confirmed that Lysine was successfully decorated on GO surface by formation of chemical bonds.Then LY-GO nanomaterials were introduced into EP coatings on the mild steel substrate.The SEM images demonstrated that distribution of LY-GO in WEP₂₀₆₀coatings was remarkably improved due to Lysine modification.The effect of LY-GO and GO nanosheets on the anti-corrosion property of the WEP₂₀₆₀coating was studied by potentiodynamic polarization test,EIS,and salt spray test.Results revealled that well-distributed LY-GO nanosheets remarkably reinforced the anti-corrosion performance of the WEP₂₀₆₀coatings.At the same filler content,LY-GO provided WEP₂₀₆₀coating with better anti-corrosion property of than GO and the corrosion rate of LY-GO/WEP₂₀₆₀coating was approximately two orders of magnitude lower than that of GO/WEP₂₀₆₀.Moreover,LY-GO could also effectively decrease the coating delamination degree during salt spray test of 500 hours.(3)Natural and nontoxic phytic acid(PA)molecules were used to functionalize GO for improving the compatibility between GO and WEP_2060Hcoating.The results of FTIR spectroscopy,Raman spectroscopy,XRD,ultraviolet–visible spectroscopy(UV-vis),XPS,and atomic force microscopy(AFM)indicated that the PA molecules was successfully decorated onto the surface of GO nanomaterials.SEM analysis revealled that the dispersion performance of GO in WEP_2060Hwas significantly enhanced owing to PA modification.The results obtained from long-term electrochemical measurements and salt spray test confirmed that addition of well-dispersed PA-GO nanomaterials could remarkably enhance the barrier and corrosion protection capability of the WEP_2060Hcoatings.