Solar Infrared Reflective Pigments
Cool metal roofs (or rather the colour pre-coated metal) contain a special grade of polyvinylidene fluoride (PVDF) resin typically referred to as Kynar, its original trade name. Kynar is related to Teflon and has become a catchall phrase for the latest versions of PVDF resins, Kynar 500 and Hylar 5000. These coatings are referenced most often in relation to cool roofs because their finishes are durable and soil-resistant, and the reflectance remains constant over the life of the roof.
Combining the PVDF resin with cool infrared reflective pigments improves the product’s thermal performance and takes 80 to 85 percent of the heat out of the coating before it has an opportunity to penetrate into the building. This leaves only a small amount in the metal to attack the building, which affects the efficiency of the thermal envelope.
Solar Energy, or “electromagnetic radiation” from the sun, consists of radiation in the wavelengths from about 250 nanometers (nm) to about 2,500 nanometers.
We can see different colors by selective reflection and absorption of various wavelengths in the visible region. We can perceive a color such as a red car, because the radiation (wavelengths of light) in the red portion of the cars pigment (approximately in the range of 650 nm) is reflected back to our eyes, while the rest of the wavelengths (400 to 650 and above 650) are absorbed by the pigment. We can’t see above 700 nm which is the infrared portion of the spectrum, so we really can’t determine what is going on there by sight.
We can feel the effects of this “Infrared Energy”, in the form of Heat! Touch your asphalt driveway, your conventional asphalt shingled roof, or your black car which has been out in the sun for a while. It’s quite Hot!! In fact some roofing products can reach surface temperatures above 190° F or more. Why is this? It’s because these materials absorb a large portion of the infrared (heat) radiation from the sun.
Composition of the Pigments
These Solar Infrared Pigments are basically synthetic mineral compounds known in the industry as CICP or Complex Inorganic Color Pigments. They are widely accepted as being the best quality pigments available. They are made by reacting mineral compounds together in a calcination process, where these minerals undergo a solid state reaction at temperatures up to 2200° F to make new color compounds.