Abstract
The synergism of hydrogen bond-type ultraviolet absorbers (UVA), such as phenyl salicylate and benzotriazole type UVA, and hindered amine light stabilizers (HALS) was investigated and compared with that of benzophenone type UVA. Phenyl salicylate and benzotriazole type UVA showed a similar synergistic and antagonistic interactions with HALS to those for benzophenone type UVA, but the synergism exceeded the antagonism. The order of their synergism of preventing photooxidation was benzotriazole > phenyl salicylate > benzophenone for UVA. The order and the degree of the synergism agreed completely with those of the regeneration of new UVA by the reaction of UVA quinones, accidentally formed by scavenging peroxy radicals, with HALS. Therefore, such generation is concluded as the essence of synergism of UVA with HALS.
