The exterior durability of most organic coatings is highly dependent upon the use of light stabilizers. The two main stabilizer categories are ultraviolet light absorbers (UVAs) and hindered amine light stabilizers (HALS). UVA chemical classes include benzophenones, cyanoacrylates, oxanilides, benzotriazoles and triazines. Today, the latter two of these classes are by far the most commercially significant to the coatings industry due to their excellent spectral coverage, high extinction coefficients and excellent photo-permanence.
HALS fit into a broader chemical family known as antioxidants but are distinguished from other materials of that class such as phosphites, lactones and hindered phenols by their cyclical mechanism, which allows for long-term efficacy in a similar way that keto-enol tautomerism permit the same for UVAs.UV radiation is known to contribute to the chemical modification of exposed paint surfaces. The deleterious effects of radiation include loss of gloss, color change, chalking, flaking and film delamination.