Preparation And Properties Of Silican Nitride Modified By ATRP And The Application In Hybrid Coatings

With the improvement of environmental requirement,the new functional composite coatings with applying nano-particles in coating system has become the focus of research.Compared to traditional coatings,the organic-inorganic hybrid coatings have better basic mechanical properties and outstanding functional characteristics.However,agglomeration of nanoparticles makes it difficult to disperse in the coating system,therefore,the premise of preparing the hybrid coatings is to modify the nanoparticles,improve its dispersibility and function.In this paper,we developed epoxy resin/Si₃N₄ hybrid coatings with using modified Si₃N₄ by ATRP method for metal corrosion.The research progression in the paper are as following:1.Amino groups and surface-initiator on the surface of Si₃N₄ were prepared.3-triethoxysilylpropylamine and chloracetyl chloride were used to introduce the initiator on the surface of nano-Si₃N₄.The effects of reaction time,temperature and raw material mass ratio on the grafting rate were investigated by single factor and orthogonal experiment.The optimum reaction conditions are determined as follows:the reaction temperature is 60?;the reaction time is 4h;the mass ratio is 0.15.The grafting rate of amination process is 3.65%,the content of initiator is 8.75×10^-5mol/g.2.The modified nano-Si₃N₄ powder with organic molecular chains on the surface was prepared.The modified nano-Si₃N₄ powder was prepared by atom transfer radical polymerization method with using methyl methacrylate/glycidyl methacrylate as monomer and Si₃N₄ prepared in the previous step as initiator.The effects of reaction temperature,raw material mole ratio and adding amount of solvent addition on the molecular weight distribution were investigated by single factor and orthogonal experiment.The optimum reaction conditions are determined as follows:the reaction temperature is 75?;the content of solvent is 30mL;the mole ratio is 1:1:3.The results show the modified nano-Si3N4 powder has good dispersibility,particle size and agglomeration decreased.3.Epoxy resin/Si₃N₄ hybrid coatings were prepared by adding Si₃N₄-ATRP into the resin emulsion.Electrochemical impedance spectroscopy was used to measure the electrochemical corrosion of the hybrid coatings and test the corrosion process of coatings in NaCl solution for different immersion times,the results illustrat that hybrid coatings with 0.75wt.%Si3N4-ATRP have better corrosion resistance.The hybrid coatings were also studied by employing the surface contact anglemeasurement,scanning electron microscope and different scanning calorimetry.The anti-corrosion mechanism of Si3N4/epoxy hybrid coatings is achieved through the shielding of hybird film.