The company Pennwalt developed a fluoropolymer coating for the building based on polyvinylidene fluoride (PVDF) (trademark Kynar500) in 1965. Since then, the PVDF coating has been used in buildings.
Rotary electrostatic spray application of PVDF coating is the most common application method. There are a 2-COAT system, a 3-COAT system, and a 4-COAT system. It has excellent resistance to fading, anti-blooming, anti-air pollution (acid rain, etc.), strong UV resistance, strong crack resistance, and ability to withstand harsh weather conditions.
The company Sames developed the powder electrostatic spray technology and the corresponding spraying equipment in 1963. Then powder coating spray technology was widely used in industrial production.
The electrostatic spray application of powder is the most common application method. The coating is good on impact resistance, abrasion resistance, corrosion resistance, weather resistance, etc. And this method is widely used in architectural and industrial products, which mainly used in windows and doors as well as other structural buildings.
The primary surface treatment of aluminum profiles used exterior is polyester powder coating. The material is affected by factors such as light, temperature, and humidity in the atmosphere, and the surface coating will have natural aging phenomena such as fading, powdering, foaming, and shedding, which affect the service life. Ordinary outdoor powder coatings are available in a 5-year warranty, and some painters can guarantee a 10-year warranty.
However, for buildings in hot and humid areas, the biggest weakness of the powder coating is that it is afraid of the sun’s ultraviolet radiation. Long-term exposure will cause natural fading. The color difference between the sunny and non-positive sides of the aluminum plate is evident after a few years. Generally, the color difference is visible after 2-5 years. At the same time, salt spray in the offshore area can cause strong corrosion on the coating surface.
There’s a test on PVDF coatings, super durable powder coatings, and exterior powder coatings. The coated samples were placed in the hot sun of Florida, USA, and exposed to the harsh environment of humid salty air for 12 years. The test result proves that the stability and durability of PVDF coatings are 30-80% higher than the other two coats. PVDF coatings are guaranteed to be used in a variety of harsh environments.
To ensure coating performance, three AAMA specifications should be referenced: AAMA2603, AAMA2604, and AAMA2605. These three specifications apply to progressively stronger levels, as indicated by South Florida outdoor exposure and laboratory accelerated testing results, as shown below.
AAMA Specifications – Organic Coatings on Aluminum
1 year, South Florida
5 year, South Florida
10 year, South Florida
1 year: “slight” chalk
5 yrs: Chalk < 8
10 yrs: Chalk < 8
1 year: “slight” fade
5 yrs: Fade ≤ 5 Delta E
10 yrs: Fade ≤ 5 Delta E
1 year: “slight” fade
5 yrs: ≥ 30% retention
10 yrs: ≥ 50% retention
5 yrs: < 10% loss
10 yrs: < 10% loss
For coating manufacturers, generally, a typical exterior powder coating can meet AAMA2603, an improved super durable powder coating can meet AAMA2604, and PVDF coating can meet AAMA2605. It can be seen that PVDF coating has excellent anti-fading, anti-blooming, anti-air pollution (acid rain, etc.) corrosion resistance, strong UV resistance, strong crack resistance, and ability to withstand harsh weather conditions. In addition to the abrasion resistance in terms of mechanical properties, impact resistance has excellent performance, especially in harsh weather and environment, showing long-term anti-fade and anti-ultraviolet properties.