UV absorbers preferentially absorb the incident UV radiation and so protect the polymer from the radiation. They absorb UV light and convert it into heat. Exposure to sunlight and some artificial lights can have an adverse effects on the useful life of polymers. A process called photo degradation takes place when UV radiation breaks down the chemical bonds in a polymer, ultimately causing cracking, chalking, color changes and the loss of physical properties. The role of the UV absorbers is to interrupt the photo oxidation process. The term UV absorber is usually used to describe compounds which do not affect transparency to visible light. Such UV absorbers are a class of stabilizers which have intense absorption up to 350 to 370 nm, but are transparent in the visible. Also known as UV screening agents and ultra violet stabilizers.
UV light consists of three different kinds including different wavelength; UV A, UV B & UV C. UV A is the most strong and dangerous for polymers. This give a range from 315nm till 400nm which needs to be absorbed to protect the polymers.
We can divide the UV absorbers into groups with different chemicals structure