| Aluminum flake has been widely applied in coatings because of its metallic luster and flop color.Due to the requirements of sustainable development of human society,traditional solvent coatings are rapidly replaced by water-based coatings,and water-based coatings have been widely used because of their low VOCs emissions.The pristine aluminum flakes react with water and generate hydrogen(H2)in water-based coatings,which reduce chemical stability,poor compatibility,decline glossiness in water-based resins and prospective safety problems for production and storage.In this paper,we prepared three types of aluminum flake microcapsules with double layered structure to overcome the above problems.Their internal corrosion layer enhances chemical stability and external hydrophilic layer improves dispersibility in aqueous systems.The main work in three parts are as follows:1.A microcapsule structure was designed to achieve corrosion resistance and hydrophilicity which consisted of aluminum flake and nano-silica.The one-step method was achieved for the assembly of nano-silica particles on surface of aluminum flakes and chemical grafting of organic chain with amino group to the shell by adjusting the conditions of hydrolysis of tetraethylorthosilicate and cohydrolysis of KH550.The results according to HG/T 2456.5-2016 test indicated that the amount of released hydrogen gas was reduced to 23.5 ml within 2 hours,which indicated that the microencapsulated aluminum flakes have good corrosion resistance.In order to explore the feasibility of large-scale preparation of aluminum flake microcapsules combined with the existing process,aluminum powders were co-milled with commercial silica particles.Water resistance test results showed that the corrosion resistance of aluminum flake microcapsules prepared by this method was limited.2.A double-layer structure with aluminum flake as core,zinc-aluminum phosphate as water-resistant passivation film and external chelated phosphate ester as pore sealing was prepared.First,a zinc-aluminum phosphate chemical transfer film was prepared under mild conditions,and then the phosphate ester was chelated on the surface to achieve the hydrophilicity and corrosion resistance of the aluminum flakes.The results showed that the aluminum flake microcapsule has good corrosion resistance and can produce no hydrogen within 2 hours,which is much higher than the industry standard.In addition,the contact angle test results showed that the contact angle of the aluminum flake microcapsules with water decreased from 93.45° to 31.34°,indicating that the hydrophilicity has been achieved.3.The flaky aluminum microcapsule was designed with aluminum flake as the core,zinc-aluminum-phosphate as the chemical transfer film on the inner layer and quaternary ammonium salt as an organic group on the outer layer.The chemical transfer film was prepared in the same manner as above.The grafting of quaternary ammonium organic chains was achieved by condensation of the quaternary ammonium salt silane coupling agents with the hydroxyl groups on the passivated aluminum flake microcapsules,thereby achieving the corrosion resistance and antibacterial.And the two kinds of quaternary ammonium salt silane coupling agents are N-trimeyhoxysilylpropyl-N,N,N-trimethylammonium chloride and dimethyloctadecyl[3-(trim ethoxy silyl)propyl]ammonium chloride.The results according to HG/T 2456.5-2016 showed that the amounts of hydrogen evolution in the two types of the prepared aluminum flake microcapsules within two hours are both 0 ml,indicating that the corrosion resistance had been achieved.Antibacterial tests showed that the two types of antibacterial aluminum flake microcapsules prepared had a certain inhibitory effect on staphylococcus aureus.The prepared phosphorus-based aluminum flake microcapsules were tested for application in Wuhan Shuanghu Coating Co.,Ltd.The results showed that the glossness was 101.2%,the DOI was 7.15,the FI was 83.1,and the adhesive strength was 0 grade. |
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