Applications Of Aromatic Ring-rich Hyperbranched Polymer In Waterborne Epoxy Anticorrosive Coatings

Waterborne epoxy anticorrosive coatings,which use water as dispersant and diluent,are environmentally friendly and are the main development direction of coatings.However,due to the introduction of too many hydrophilic groups and the change of film-forming mechanism,the medium resistance and anti-corrosion performance of waterborne epoxy resin anti-corrosion coatings are greatly reduced,which can not meet the application requirements in industrial heavy-duty anti-corrosion and other fields.Therefore,improving the anti-corrosion performance of waterborne epoxy resin coating is a difficult problem expected to be solved in the world coating industry.Epoxide terminated hyperbranched polymers has high molecular weight,high functionality,low viscosity and more free volume in the molecule.It is expected to obtain epoxy resin coatings with low viscosity,high toughness and high anti-corrosion performance.So in this work,a series of aromatic ring-rich hyperbranched polymers were designed and synthesized to modify high solid and solvent-free anti-corrosion epoxy coatings with the propose of improving the anti-corrosion performance and toughness of the coatings as well as reducing VOC;Meanwhile,in order to improve the stability of emulsion and water resistance and corrosion resistance of waterborne epoxy coating,a reactive emulsifier was synthesized for the preparation of hyperbranched polymer modified waterborne epoxy emulsion by reverse conversion method.Besides,the fluorescent propertiesof the hyperbranched polymers were studied.The main contents of this dissertation are as follows:1.A series of aromatic ring-rich,epoxide terminated hyperbranched polymers（EHBP）were designed and synthesized by A₂+B₃proton transfer polymerization.The effects of A₂monomer on the quantum yield and fluorescence lifetime of EHBP were studied.It was found that the epoxy terminated hyperbranched polymers EH1011 derived from BINOL had the highest quantum yield of 81.47%.EH1011 has two different emission peaks when excited at 355 nm and 401 nm respectively,showing excitation wavelength-dependent emission.EH1011 can be used for iron ion detection and simple anti-counterfeiting.A fluorescent coating was prepared by curing EH1011 with DETA curing agent.The fluorescence brightness of EH1011/DETA coating changes in three stages with immersion time,which is in correspondence with the changes in phase angle and impedance of the coatings from EIS measurements.Moreover,before visible coating failure,the fluorescence brightness changes significantly,demonstrating its coating failure prediction ability.2.EHBP was added into commonly used E51 epoxy resin as a modifier,thus preparing high performance coating resins.Firstly,it was found that the solution viscosity of EHBP/E51 is lower than that of neat E51,indicating that EHBP can be used for reducing the VOC of high solid epoxy coating.Secondly,the results of EIS measurements show that when the addition amount of EHBP is 7%,the modified coating maintains its high phase angle（in a long time and wide frequency range）and high impedance value（at low frequency）in acid,alkali and salt solutions,demonstrating its excellent long-term anti-corrosion performance.Meanwhile,it was found that the anti-corrosion properties of the modified coatings increase with the increase of the number of aromatic rings of A₂monomers.Thirdly,the impact toughness of the modified coating is higher than that of unmodified one by 125%,while T_gis also slightly improved,achieving simultaneous toughening and reinforcing by the addition of EHBP.3.A coating formulation that is suitable for air spray was obtained by investigating the effects of different diluents and adjusting the viscosity of the solvent-free epoxy coating.The VOC of the EHBP-modified,solvent-free epoxy coating is 51g/L,which meets the standards of GB/T 38597-2020.It was found that the corrosion resistance of the modified coating also increases with the increase of the number of aromatic rings of A₂monomer.Furthermore,the effects of the type and amount of curing agent on the anti-corrosion performance were studied too.The prepared solvent-free,epoxy-based,anti-corrosion varnish can stand 3000+h neutral salt spray test.At the same time,the impact toughness of the coating is improved by more than 30%,whereas T_gis slightly reduced.4.A reactive emulsifier was synthesized,and the emulsifier system was optimized.The emulsifying properties of the reactive emulsifier and the stability of the emulsion emulsified by it were studied.Then,a waterborne epoxy emulsion with small particle size,narrow distribution and good stability（>18 months）was obtained by phase inversion method,based on the optimized emulsifier system.The equivalent circuit modeling results of EIS data show that the reactive emulsifier can improve the water resistance of the coating（reduce the volumetric water absorption of the coating by 32%）,and improve the anti-corrosion performance of the coating.The finally obtained WBEH8167 color paint with 120 cm impact toughness,shows 1.5 mm average unilateral corrosion width（all less than 2 mm）after 1176 h neutral salt spray test,thus can be used in the field of heavy corrosion protection.