Weather Resistant Coating of Organic Silicon Resin
Aug 14, 2024
The coatings used outdoors (i.e. weather resistant coatings) need to withstand wind, sun, rain, alternating cold and heat, ultraviolet radiation, etc. Due to the absence of unsaturated bonds in the molecules of silicone resin, it has excellent resistance to atmospheric corrosion. UV radiation does not easily cause it to crack or crosslink, and long-term exposure to outdoor sunlight results in no loss of gloss, powdering, discoloration, or intact paint film. Its weather resistance is excellent.
For example, pure silicone resin coating can be exposed to outdoor sunlight for 12 years without loss of gloss, discoloration, or powdering, and the coating is intact, proving its outstanding weather resistance. It can be made into non powdering coatings with a large amount of powdered pigments. However, due to the high production cost of silicone resin and unsatisfactory curing properties and adhesion to the substrate, it is rarely directly used as a base material for weather resistant coatings.In the coating industry, the characteristic of organic silicon resin is utilized to improve other organic resins, mainly used as weather resistant coating base materials. The main varieties include organic silicon modified alkyd resin, polyester resin, acrylic resin, polyurethane resin, etc., to manufacture long-lasting weather resistant and decorative coatings with excellent performance, which is very effective.
In recent years, there has been great progress in modification work, which is one of the main directions for the development of organosilicon resins for coatings. This type of organic silicon modified resin paint is cheaper than organic silicon resin paint, can dry at room temperature, is easy to apply, and has greatly improved weather resistance, decorative properties, heat resistance, insulation, water resistance, and other properties compared to unmodified organic resin paint.
The weather resistance of modified resins is directly proportional to the organic silicon content in the formula. Generally, the organic silicon content in modified resins that are dry at room temperature is 20% to 30%; The organic silicon content in the drying modified resin can reach 40%. The weather resistance of modified resins is also related to the composition of organosilicon oligomers used as modifiers. The more Si-0-Si bonds in organosilicon oligomers, the better their weather resistance. The number of Si-0-Si bonds is the determining factor of resin weather resistance. Therefore, in formula design, it is better to select organosilicon oligomers with a higher ratio (number of methyl groups/number of phenyl groups) among organosilicon weather resistant resins with the same content.
The weather resistance of coatings modified with organosilicon such as alkyd, polyester, and polyacrylate is significantly improved, making them suitable for long-term, high decorative protective coatings for outdoor use. Especially, organosilicon modified alkyd resin coatings not only maintain their original air drying characteristics, but also greatly improve their weather resistance.Organosilicon modified polyurethane coatings are widely used for the protection of aircraft skins, large tank surfaces, building roofs, and cultural relics. The weather resistance of organic silicon modified room temperature dry type alkyd resin paint is improved by more than 50% compared to general unmodified alkyd resin paint, and the gloss and color retention are doubled.
Due to the improved weather resistance, equipment maintenance costs can be reduced by 75%, making it more economical than using unmodified alkyd resin paint. Room temperature dry organic silicon modified alkyd resin paint is commonly used as a heavy-duty anti-corrosion paint. It uses metal soap as a catalyst to cure at room temperature and is a relatively inexpensive universal variety. It is suitable for permanent steel structures and equipment, such as high-voltage transmission line towers, railway bridges, freight cars, oil drilling equipment, power stations, agricultural machinery, etc. It is also suitable for coating the water parts of marine vessels under harsh weather conditions.
After 10 years of use, the paint film is still completely destroyed and the appearance is good. Polyurethane modified silicone resin weather resistant coating has better chemical stability as an outdoor coating than alkyd modified silicone resin. Acrylic and polyester modified silicone resin weather resistant coatings, generally using melamine resin as a curing agent, are used for waterproof coatings on civil engineering, roofs, or walls.
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