Preparation And Application Of PANI/CNT Nanocomposites In Waterborne Coatings

The use of zinc-rich and other heavy metal corrosion protection paints is a traditional method to reduce the corrosion rate of metals,but it has environment pollution problems such as organic volatiles(VOC)and heavy metal emissions.The development of environmentally friendly new coating systems(no heavy metals and low VOC emissions)is urgent.Conductive polymers such as polyaniline are considered to be a green corrosion protection material with application potential.However,polyaniline corrosion protection materials have not yet been commercialized because of the metal corrosion protection mechanism of polyaniline is not completely clear and its electrochemical corrosion protection effect only appears in the environment of pH<5.This paper aims at the problems of coatings and corrosion protection conductive polymers.It uses nanocomposite methods to obtain carbon nanotubes and polyaniline(PANI/CNT)with excellent corrosion protection function due to the complementary and functional coupling of different nanomaterials and reveals the corrosion protection mechanisms,then studies the PANI/CNT nanocomposites as a functional anticorrosive additive to prepare a completely environmentally friendly organic nano-coating material.Specific research contents are as follows:1.Preparation of PANI/CNT nanocompositeThe dendritic-like PANI/CNT nanocomposite was successfully prepared by oxidative polymerization of aniline adsorbed on the surface of sub-micron calcium carbonate and carbon nanotubes in acidic aqueous solution.The results show that the PANI/CNT nanocomposite presents a core-shell structure,the morphology which can be regulated by the mass ratios of aniline monomers to carbon nanotubes.The "charge transfer bridge" is formed between PANI and CNT through π-π stacking,which makes it still have excellent redox activity in a wide pH environment.2.Effect of doped acid on the performance of PANI/CNT nanocomposite and its metal corrosion protectionDoping PANI in PANI/CNT nanocomposite with organic phosphonic acid and hydrochloric acid,respectively.And filling them in water-based acrylic coating to prepare nanocomposite coatings.The results show that the CNT is selected to composite with PANI can not only improve the dispersion of nano-PANI in the coatings,but also expand the electrochemical activity of PANI from acid to neutral.The corrosion protection mechanisms of PANI are revealed to be "Nanobarrier effect","Anode protection" and "Cathode suppression" through organic phosphonic acid doping PANI/CNT nanocoating.The organic phosphonic acid doping PANI/CNT nanocomposites with excellent corrosion protection performance have great potential to replace the toxic heavy metal in the corrosion protection coating field.3.Application of PANI/CNT nanocomposites in waterborne coatingsThe PANI/CNT were filled in waterborne acrylic coatings to prepare nanocoatings.The results show that when the filling amount is 0.5-1 wt%,the dispersant PT-04,the thickness is more than 25 μm and the curing temperature is 160℃,the corrosion resistance of the waterborne nano-coating is the best;the addition of nanomaterials has no negative effect on the mechanical properties of coatings and the composite of PANI/CNT is more likely to form a cross-linked network structure in waterborne coatings;Compared with the unfilled waterborne coating and filled with PANI coating,the coating filled with PANI/CNT nanocomposite has the best corrosion resistance in neutral environment.