At present, the types of coatings used for color-coated steel plates include polyester coatings (PE), fluorocarbon coatings (PVDF), silicon modified coatings (SMP), high weather resistance coatings (HDP), acrylic coatings, polyurethane coatings (PU), plastic Sol paint (PVC), etc.
- The polyester coating has good adhesion to the material. The color-coated steel plate is easy to process and form, the price is low, the product is many, and the color choice is large. Under direct exposure in general environment, the anti-corrosion life can be as long as 7-8 years. However, in industrial environments or heavily polluted areas, its service life will be relatively shortened. However, the UV resistance and film crush resistance of polyester coatings are not ideal. Therefore, the use of PE coatings still needs to be restricted. It is typically used in areas with less air pollution or products that require multiple molding and processing.
- Since polyester contains active groups -OH/-COOH, it is easy to react with other macromolecules and polymers. In order to improve the light resistance and pulverization of PE, silicone resin with excellent color retention and heat resistance is used for denaturation reaction, and the denaturation rate with PE can be between 5% and 50%. SMP provides better durability of steel plates, and its anti-corrosion life can reach 10-12 years. Of course, its price is also higher than that of PE, but due to the unsatisfactory adhesion of silicone resin to the material and the formability of processing, SMP color-coated steel plate is not suitable for occasions requiring multiple forming processes, and most of them are used for building roofs and exterior walls.
- The high weather resistance polyester coating is better than the ordinary silicon modified polyester coating, and the outdoor weather resistance is up to 15 years. In the process of synthesizing polyester resin with high weather resistance, monomers containing cyclohexane structure are used to achieve a balance between resin flexibility, weather resistance and cost. Aromatic polyols and polyacids are used to reduce the UV absorption of the resin and achieve high weather resistance of the coating. Add UV absorbers and steric blocking amines (HALS) to paint formulations to improve the weatherability of the paint film.
Fourth, the plastisol has good water resistance and chemical resistance. It is generally a high solid content coating with a coating thickness of 100-300 μM, which can provide a smooth PVC coating or a light embossing treatment as an embossed coating; since the PVC coating is a thermoplastic resin with a high film thickness, Therefore, it can provide good protection for the steel plate. But PVC has poor heat resistance.
- Due to the strong bond energy between PVDF chemical bonds, the coating has good corrosion resistance and color retention. It is a more advanced product in Baosteel’s color steel coil coatings for construction, with large molecular weight and direct bonding structure. Therefore, in addition to chemical resistance, its mechanical properties, UV resistance and heat resistance are also outstanding. Under normal circumstances, the anti-corrosion life can be as long as 20-25 years. In recent years, fluororesins copolymerized with chlorotrifluoroethylene and vinyl ester monomers have been widely used in my country, and are widely used in building exterior walls and metal panels. Due to the use of easily hydrolyzed vinyl ester monomers, the fluorine content is about 30% lower than that of PVDF, and its weather resistance has a certain gap with PVDF.
- Acrylic resin has good comprehensive performance and high price, and is only used in specific fields (such as containers).