Preparation And Anticorrosive Performance Of Waterborne Alkyd Mica Iron Oxide

The rapid development of modern industry has caused a large number of metal substrates to be used in manufacturing,construction and other fields,prompting the development of anticorrosive coatings for metal protection.Alkyd resin is widely used in the coating of various manufacturing and construction industries because of its low synthesis cost,bright and full coating film and superior comprehensive performance.With the awareness of environmental protection,the functionalization,modification and water-based of alkyd resin have become the focus of attention.Micaceous iron oxide is an excellent antirust pigment with sheet structure,but the particles easily interact to cause agglomeration,affecting its dispersion and use in the coating,so it must be modified.In this thesis,the basic alkyd resin of maleic anhydride was synthesized by fatty acid method.For the shortcomings of low hardness and poor water resistance of waterborne alkyd resin,styrene and acrylic monomers were used to modify the alkyd resin.A modified water-based alkyd resin having good stability and coating film properties is obtained.On this basis,a water-based alkyd micaceous iron oxide anticorrosive coating with good water resistance,salt spray resistance and corrosion resistance was prepared by optimizing the surface modification of micaceous iron oxide.The main research contents are as follows:(1)The alkyd resin was prepared from soybean oil fatty acid,linoleic acid,trimethylolpropane,pentaerythritol,phthalic anhydride,isophthalic acid,cis-1,2,3,6-tetrahydrophthalic anhydride,benzoic acid and maleic anhydride.The synthetic formula and process of the resin were studied and optimized.The results show that the optimum preparation conditions are the oil length of 45%-50%,K value is 1.06-1.08,excess of alcohol is 25%-30%,the mass ratio of soybean oil fatty acid to linoleic acid is 5:1,the 1:1 mass ratio of trimethylolpropane to pentaerythritol and the 2:1-2.5:1 mass ratio of phthalic anhydride to isophthalic acid,the amounts of benzoic acid,tetrahydrophthalic anhydride and maleic anhydride are 6%,15%and 7%-8%,respectively.(2)The alkyd resin was modified by styrene,acrylic acid and a small amount of silane coupling agent monomer.The effects of initiator,neutralization degree,the amount of modified monomer and the ratio of modified monomer on the properties of alkyd resin were investigated,and the best process of modification stage was optimized.FT-IR,GPC,nanoparticle size and zeta potentiometer were used to characterize water-borne alkyd resin.The results show that the modified resin has excellent film properties when the mass ratio of total modified monomers to alkyd resin is 7:10,the 1:1 mass ratio of styrene to methyl methacrylate,the ratio of hard monomers to soft monomers is 16:1,the neutralization degree is 100%,the dosage of acrylic acid,vinyl triethoxysilane and benzoyl peroxide is 9%,3%and 3%,respectively.(3)The effects of stearic acid,silane coupling agents(KH550,KH570 and KH792)on the modification of micaceous iron oxide were investigated.The results show that KH792 had the best modification effect and the best dosage was 1.2%.FT-IR results show that KH792 has been chemically bonded with hydroxyl groups on the surface of micaceous iron oxide powder;Polarizing microscope showed that the micaceous iron oxide modified by silane coupling agent KH792 dispersed more evenly without agglomeration.(4)The waterborne alkyd micaceous iron oxide anticorrosive coating was prepared by using the modified waterborne alkyd resin and the modified micaceous iron oxide of KH792.The results of salt spray test show that the coating with 15%modified micaceous iron oxide had no obvious change after 168 h salt spray test,and the anticorrosion effect was the best;The results of salt spray resistance test show that the coating with 15%modified micaceous iron oxide did not change significantly after 168 h salt spray test,and the anticorrosion effect was the best;The results of polarization curves show that when the amount of micaceous iron oxide is 15%,the coating has the lowest corrosion current density(I),the slowest corrosion rate and the best anti-corrosion effect.