Polyester (PE, Polyester)
PE coating has good adhesion to materials, prepainted galvanized steel coil in stock is easy to process and shape, cheap and products, color and gloss options. In the general environment under direct exposure, its corrosion fixed number of year for up to seven to eight years, but in an industrial environment or polluted areas, its service life is relatively lower, but polyester coating with UV resistance and coating resistance to pulverization, not ideal, so the use of the PE coating still need is limited by some, commonly used in air pollution is not serious or were in need of processing products for many times.
Silicone Modified Polyester (SMP)
Because of polyester containing active group – OH / – COOH, extremely easy and other polymer chemical and physical reactions, for improved resistance to sunlight and pulverization of PE, color retention and excellent heat resistance of Silicone resin modified reaction, and degeneration of PE ratio is between 5% – 50%, SMP provides better the durability of the steel, the corrosion life up to lO – 12, of course, its price is more PE is high, but because of the Silicone resin adhesion and processing of material formability is not ideal, therefore the SMP painted steel plate does not apply to the need to repeatedly forming, Most of them are used for roofs and exterior walls of buildings.
Durable polyester (HDP, High durable Polyester)
As for the disadvantages of PE and SMP, HYDRO company (now acquired by BASF) of the UK and BECKER of Sweden developed HDP polyester coating with weather resistance of 60-80% of PVDF coating in early 2000, which is superior to ordinary silicone-modified polyester coating with outdoor weather resistance of 15 years. High weather resistant polyester resin in the synthesis of cyclohexane structure monomer, to achieve the flexibility of the resin, weather resistance, and cost balance, use no aromatic polyol and polyacid to reduce the absorption of UV light resin, achieve the coating high weather resistance. Uv absorbent by China prepainted color galvanized coil factory and steric hindrance amine (HALS) are added to the paint formulation to improve the weathering resistance of the film. High weather resistant polyester coil coatings have been recognized by the foreign market, the cost performance of the coating is very outstanding.
Because of PVDF chemical bonds and bonds, there is a strong bond energy, so the coating has good corrosion resistance and color retention, in building steel plate coating industrial belt, it belongs to the most advanced products, and the molecular weight and structure type of key, so in addition to the chemical resistance, mechanical properties, resistance to ultraviolet radiation and heat resistant performance are also very prominent. Under normal circumstances, the corrosion protection life can be as long as 20 to 25 years. In recent years, fluororesin containing trifluoroethylene chloride and vinyl ester monomer copolymerization has become popular in China, which is widely used in building external walls and metal plates. Due to the use of easily hydrolyzed allyl ester monomer and the content of fluorine is about 30% lower than PVDF, so there is a certain gap between its weatherability and PVDF. For the fluorocarbon coating produced by Chinahengzesteel, the PVDF content of the coating is not less than 70% (the other is propylene acid resin).