Application research of modified silica micro powder in powder coatings

 Powder coatings were first developed in the 1950s by uniformly mixing polymers such as epoxy resin, polyester resin, polyurethane, polyacrylic acid, pigments, additives, etc. Powder coating is an environmentally friendly coating with a solid content of 100% and no organic volatile compounds (VOCs) produced. Titanium dioxide is the main white pigment in powder coatings, with high coverage and strong coloring power. However, the production process of titanium dioxide is complex, causing significant environmental pollution and high prices. Therefore, some substitutes have emerged in the market, such as calcium sulfate whiskers, modified calcium carbonate, zinc oxide, etc., which are all used in coatings.

Silicon micro powder (SiO2) is a tasteless, non-toxic, and pollution-free non-metallic material with advantages such as high hardness, low thermal conductivity, high temperature resistance, stable insulation and chemical properties. Most of the silicon micro powders on the market are obtained through low-cost physical methods. Currently, silicon micro powders are widely used in rubber, plastics, ceramics, and coatings.

By utilizing the structural similarity between silicon micro powder and titanium dioxide, Wang Pengzhu et al. applied silicon micro powder titanium dioxide composite powder to latex coatings, and the pencil hardness of the coating was significantly improved compared to latex coatings made entirely of titanium dioxide. Liu Zongwang and others added silicon micro powder to unsaturated polyester insulation paint, which improved the water absorption rate, electrical strength, and volume resistivity of the coating. Puig et al. studied the excellent mechanical and electrochemical properties of powder coatings after adding organic modified silica. At present, there is a lack of research reports on the wear resistance, high hardness, and durability of epoxy/polyester resin powder coatings. This article explores the use of silicon micro powder in epoxy/polyester resin powder coatings to improve the mechanical properties such as hardness and impact resistance of the coatings, for surface coating of automobiles, home appliances, hardware, building materials, and oil pipelines.

The optimal process conditions for rich silicon powder coating are: spraying voltage of 70kV, curing temperature of 180 ℃, and curing time of 20min; Powder coatings containing silicon micro powder have a decrease in paint film whiteness and glossiness, but an increase in paint film hardness. When the ratio of silicon micro powder to titanium dioxide is 1:1, the performance of powder coating film is better; The powder coating containing silicon micro powder has improved T5 and Tp by 30 ℃ and 7 ℃ respectively.