The purpose of surface modification of ultrafine powder is: 1. In order to improve or change the dispersibility of powder particles; 2. Improve durability, such as resistance, light resistance, heat resistance, weather resistance, etc.; 3. Improve particle surface activity; Adding new physical, chemical and mechanical properties and new functions to the surface of the particles to increase the added value of the powder.
At present, there are many methods for surface modification, and the classification method varies depending on the angle of analysis of the problem. The powder surface modification methods are divided into six categories, namely: surface coating modification, surface chemical modification, mechanical force chemical modification, capsule modification, high energy modification, and precipitation reaction modification.
Let us introduce the principle and function of Surface chemical modification. Surface chemical modification is accomplished by chemically reacting or chemisorbing the surface modifier with the surface of the particle. Shirai et al. use a hydroxyl group on the surface of inorganic particles to graft a group on the surface of ultrafine particles such as Si, TiO2 and silica to initiate polymerization. Then, these groups are used to initiate polymerization of the vinyl group on the surface of the powder. The reaction effectively improves the dispersibility of the ultrafine powder in an organic medium. Li et al. found that acrylic monomers can be directly grafted onto the surface of carbon black particles under certain conditions. From the observation of transmission electron microscopy, it is found that the long chain of polyacrylic acid grafted contains The ionic hydrophilic group can better extend the steric hindrance barrier in the aqueous medium, preventing the re-aggregation of the carbon black particles, so that the carbon black particles are uniformly dispersed and the dispersion stability is increased.
M aharu Y amatoto et al. synthesized a macromolecular silane coupling agent and grafted it onto the surface of titanium oxide, so that titanium oxide was well dispersed in an organic solvent. Boven et al. and Tsubokaw a et al. respectively introduced an azo group and a peroxy group on the surface of the silica to initiate methyl graft polymerization. Zhang Wengong et al. used a self-made aluminate coupling agent to modify the surface of calcium carbonate powder. After modification, the hygroscopicity and oil absorption of calcium carbonate decreased, the particle size became smaller, and it was easy to disperse in organic medium. The heat stable temperature was more than 300. °C. Jesion.owski et al. used a mercaptosilane, a vinyl silane, and an aminosilane coupling agent to surface-treat the silica. The test results show that after the first two treatments, the hydrophobicity of the particles increases, the number of surface hydroxyl groups decreases, resulting in a decrease in secondary agglomeration; while the aminosilane coupling agent has no such effect, mainly because of the latter molecular structure. In addition to reacting with the hydroxyl groups on the surface of SiO2, the amino groups form intermolecular hydrogen bonds which in turn cause agglomeration of the particles.
M aharu Y amatoto et al. synthesized a macromolecular silane coupling agent and grafted it onto the surface of titanium oxide, so that titanium oxide was well dispersed in an organic solvent. Boven et al. and Tsubokaw a et al. respectively introduced an azo group and a peroxy group on the surface of the silica to initiate methyl graft polymerization. Zhang Wengong et al. used a self-made aluminate coupling agent to modify the surface of calcium carbonate powder. After modification, the hygroscopicity and oil absorption of calcium carbonate decreased, the particle size became smaller, and it was easy to disperse in organic medium. The heat stable temperature was more than 300. °C. Jesion.owski et al. used a mercaptosilane, a vinyl silane, and an aminosilane coupling agent to surface-treat the silica. The test results show that after the first two treatments, the hydrophobicity of the particles increases, the number of surface hydroxyl groups decreases, resulting in a decrease in secondary agglomeration; while the aminosilane coupling agent has no such effect, mainly because of the latter molecular structure. In addition to reacting with the hydroxyl groups on the surface of SiO2, the amino groups form intermolecular hydrogen bonds which in turn cause agglomeration of the particles.
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