| Nano-TiO2 has high chemical stability,thermal stability and anti-aging properties,and is widely applied in plastics,paints,coatings and inks.Thus we anticipate that nano-TiO2 may be used as a filler for waterborne polyurethane coatings to improve the corrosion resistance of composite coatings.However,nano-TiO2 has strong surface activity and high surface energy,which hinders its uniform dispersion in water-based coatings.Therefore,we used aluminum octadecate sulfate,silane coupling agent KH550 and graphene oxide to modify the nano-TiO2 to improve its dispersibility and compatibility with the polymer matrix.Furthermore,AKT/water polyurethane composite coating,TG/water polyurethane composite coating and KTNTs/water polyurethane composite coating were prepared by blending.Investigate the water resistance,thermal stability and corrosion resistance of the three composite coatings.The main contents and research results of this thesis are as follows:First,the inorganic-organic composite modification of nanometer TiO2 was carried out with aluminum octadecate sulfate and silane coupling agent KH550.The best preparation process of AKT nanoparticles is that the addition amount of alumina is 4%of nano-TiO2,the addition amount of KH550 is 3%,the reaction temperature is 80℃,and the reaction pH vaule of 9.Then AKT/water polyurethane composite coatings were prepared by blending.The composition and structure of nano-TiO2 before and after modification were analyzed by means of Fourier transform infrared spectroscopy(FT-IR),X-ray diffractometer(XRD)and scanning electron microscope(SEM).And through the water absorption test,contact angle test,thermogravimetric test(TGA)and electrochemical impedance spectroscopy(EIS)to test the water resistance,thermal stability and corrosion resistance of the composite coating.It has been found that both KH550 and alumina are successfully attached to the surface of nano-TiO2,Introducing AKT nanoparticles helps to improve the water resistance,thermal stability and corrosion resistance of waterborne polyurethane coatings.When the amount of AKT reaches 0.7%,the thermal stability of the composite coating is optimal.The thermal decomposition temperature is increased by 16℃ relative to the pure waterborne polyurethane coating,and the water contact angle is increased from 57° to 87°.At the same time,the corrosion resistance of the composite coating has also been greatly improved.The coating resistance value of the composite coating can reach 5.05 ×106 Ω·cm2.The corrosion current density is 5.21 ×109A·cm-2,which is more than 2 orders of magnitude lower than that of pure waterborne polyurethane coating,and the corrosion inhibition rate can reach 99.54%.Long-term immersion observation of the composite coating revealed that the composite coating had an effective corrosion protection time of 72 h,and the protective effect of the coating weakened after the immersion time exceeded 120 h.Used silane coupling agent KH550 to load nano-TiO2 on the surface of graphene oxide,TG composite particles were prepared.TG/water polyurethane composite coatings were prepared by blending.The composition and structure of nano-TiO2 before and after modification were analyzed by means of FT-IR,XRD and SEM.And through the water absorption test,contact angle test,TGA and EIS to test the water resistance,thermal stability and corrosion resistance of the composite coating.It has been found that nano-TiO2 was successfully loaded on the surface of graphene oxide.Introducing TG composite particles helps to improve the water resistance,thermal stability and corrosion resistance of waterborne polyurethane coatings.When the amount of TG added reaches 0.9%,the water resistance of the composite coating is optimal.The water absorption rate is reduced by 1.3%relative to the pure waterborne polyurethane coating,and the thermal decomposition temperature is increased from 283℃ to 300℃.At the same time,the corrosion resistance of the composite coating has also been greatly improved.The coating resistance value of the composite coating can reach 7.89×106Ω·cm2.The corrosion current density is 2.56×10-9A·cm-2,and the corrosion inhibition rate can reach 99.81%.Titanate nanotubes were prepared by hydrothermal method of rutile nano-TiO2 as the starting material.Titanate nanotubes were modified by using silane coupling agent KH550 to obtain KTNTs nanotubes.KTNTs/water polyurethane composite coatings were prepared by blending.The composition and structure of the titanate nanotubes before and after modification were analyzed by means of FT-IR,XRD and SEM.And through the water absorption test,contact angle test,TGA and EIS to test the water resistance,thermal stability and corrosion resistance of the composite coating.It has been found that the silane coupling agent KH550 was successfully grafted on the surface of nanotubes,and the nanotubes were H2Ti3O7 titanic acid.Introducing KTNTs nanotubes helps to improve the water resistance,thermal stability and corrosion resistance of waterborne polyurethane coatings.When the amount of KTNTs added reaches 0.5%,the thermal stability of the composite coating is optimal.The fastest thermal decomposition rate of the composite coating is 2%/min higher than that of the pure waterborne polyurethane coating,and the water contact angle is increased from 57° to 91°.At the same time,the corrosion resistance of the composite coating has also been greatly improved.The coating resistance value of the composite coating can reach 7.58 ×107 Ω·cm2,the corrosion current density is 3.20 ×10-9A·cm-2.The corrosion inhibition rate can reach 99.87%.Observing the composite coating for a long time,we found that the effective protection time of the coating was 120 h,and it still had a good protection effect after the immersion time exceeded 360 h. |
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