Preparation And Anticorrosion Properties Of Carbon Nanotube/polyaniline Core-shell Composites

The conducting polymer polyaniline(PANI)has been widely used in the field of anticorrosion materials because of its environmental friendliness,electrical conductivity and electrochemical activity.A large number of literature reports,differently from epoxy resin and other conventional anticorrosion coatings,green polyaniline coatings with the electrochemical activity property of PANI can have electrochemical corrosion protection,which greatly improves the corrosion protection efficiency.However,the occurrence of deprotonation of PANI when pH>4 may result in the loss of conductivity and electroactivity due to the unique protonic acid doping mechanism of PANI.Thus,it is difficult to have electrochemical corrosion protection in the application of marine corrosion protection with high pH values(pH>7),which has become a major obstacle in the application of anti-corrosion.In this reseach,we focus on how to make PANI to maintain the electrochemical activity in high pH environment and study the structure and thermoelectric properties of carbon nanotubes doped PANI.The anticorrosion mechanism and performance of the coatings filled with carbon nanotubes doped PANI are also discussed.(1)Carbon nanotube/polyaniline(C-PANI)composites were prepared by in situ polymerization with carboxylic carbon nanotubes as charge transfer doping agent.Transmission electron microscopy(TEM),fourier transform infrared spectroscopy(FTIR),ultraviolet-visible spectroscopy(UV-Vis),X-ray diffraction(XRD),thermogravimetric analysis(TGA),cyclic voltammetry(CV)tests and electric conductivity test were carried out to characterize the strctures and properties of C-PANI composite.The results show that the C-PANI composite present a core shell structure,the morphology and microstructure of which can be tailored through varying the mass ratios of carboxylic carbon nanotubes(c-MWNTs)to aniline.Compared with polyaniline(PANI),the thermal stability and electrical conductivity of C-PANI composites were significantly improved.These composites form a new charge transfer bridge through ?-? stacking and hydrogen bonding interactions,resulting in a high electrochemical activity in acidic,neutral and alkalic(even at pH of 12)environments.(2)The carbon nanotube/polyaniline(C-PANI)composites were filled in epoxy modified acrylic resin(EA)with different proportion to prepare the EA composite coating.Polyaniline(PANI),graphene sheets(Graphene),graphene sheets/polyaniline(G-PANI)as anticorrosive fillers,were also compared.Optical microscope(OP),cyclic voltammetry(CV)tests,EIS and Tafel plot electrochemical test,X-ray photoelectron spectroscopy(XPS)were carried out to study performance of different fillers and coatings.The results show that the anticorrosion performance of C-PANI filled EA composite coatings was significantly improved when compared with the pure EA coating,and the filling amount of 3wt%was the best.The dispersion of C-PANI in EA coating was the best among the four different anticorrosive fillers,and the coating showed superior anticorrosion performance,which is closely related to the best electrochemical activity of C-PANI in a wide range of pH environments.Moreover,C-PANI filled EA composite coating presented as electrochemical corrosion protection in acidic solution and physical barrier to corrosion in the neutral and alkaline solution.(3)According to a certain formula to prepare epoxy slurry,polyaniline(PANI),carbon nanotube/polyaniline(C-PANI),and graphene sheets/polyaniline(G-PANI)were used as anticorrosive fillers into epoxy slurry,prepared into several different filled epoxy composite coatings.The thickness testing,mechanical testing,surface resistance test,immersion test and salt spray test of the coating were carried out to investigate the effect of polyaniline-based materials on the comprehensive properties of epoxy coatings for the purpose of revealing the application value of C-PANI in epoxy slurry.The results show that the thcknesses of all coatings prepared by spraying method were basically maintained at 40±5?m.Among them,the pure epoxy coating has excellent mechanical property,the join of PANI,C-PANI and G-PANI has no negative effect on its mechanical properties.In contrast,the C-PANI filled epoxy composite coating has the best antistatic properties because of its easiness to form a conductive network in epoxy slurry,and its better dispersbility make the coating have the best medium resistance and salt resistance.