UV absorbers for coatings mitigate the damaging effects of the sun. Adding these products to a surface preserves the color brilliance and lifespan of ultraviolet-sensitive products. Do not confuse UV absorbers with blockers. These do not block ultraviolet light. Instead, UV absorbers sacrifice themselves to preserve the polymers they protect. These products compete with the surface material for the UV radiation from the sun. Because these additives have a proclivity for drawing in ultraviolet rays, they prevent the rays from reaching the substrate. By absorbing sunlight instead of letting it reach the polymer, UV absorbers protect the coating.
Because nothing can destroy energy, the radiation the UV absorber takes in must go somewhere. These products typically change the energy from UV radiation into heat. UV absorbers transmit the absorbed energy through radiating the heat. In this manner, these absorbers safely release the UV radiation in a way that does not cause damage to the material they protect.
The amount of UV absorber needed depends on its concentration and the surface's thickness. The relationship between absorber concentration and surface thickness is not linear. Higher levels reduce effectiveness. Therefore, thicker materials will need higher-than-predicted concentrations. To find the right absorber, formulators need to conduct extensive tests to find the concentration required to prevent photodegradation. Not all products absorb across the full UV wavelength spectrum. Since these products typically absorb UV rays and not visible light, they appear transparent. Above 400 nm in wavelength, UV absorbers should not block as many rays to avoid blocking blue light waves, making the material beneath appear yellow.
While other forms of UV protection regenerate themselves, UV absorbers will wear out over time. Though the wearing takes place very slowly, it still happens. To avoid problems with UV damage to the material, reapplication of the coating with absorbers must occur periodically or another means of protection sought. Alternatively, use UV absorbers for short-term solutions, such as with disposable products or those only subjected to periodic sun exposure.
