English Abstract

Light Stabilizers, Approach for Prevention of Polymer Degradation

Additives Solution Department, Polymer Additives R&D Laboratory, ADEKA Corporation, Saitama-city, Saitama, Japan
Nippon Gomu Kyokaishi,(2018),91(12),454-459 General Review in Japanese

Polymer degradation is associated by autoxidation reaction induced by heat, light, mechanical stress, and etc. This article describes mechanistic aspects of polymer autoxidation, particularly focusing on a photo-oxidation, and the role of light stabilizers in the prevention of undesirable photo-degradation.
Ultraviolet absorbers (UVA) and hindered amine light stabilizers (HALS) are typical additives that prevent the photo-degradation of plastics. UVA absorbs ultraviolet light with high energy to suppress the light-induced dissociation reaction and generation of radicals. The energy dissipation process of absorbed light by UVA depends on the chemical structures, such as benzotriazole, triazine, cyanoacrylate and so on.
In the meanwhile, HALS works as an radical scavenger to avoid the initiation of the autoxidation reaction induced by the exposure to the ultraviolet light. Most of the commercially available HALS have characteristic N-H or N-methyl (Me) group, which may interact with acidic additives, such as sulfur-containing antioxidant, pigments, and inorganic fillers, to lead an antagonistic action of antioxidation. Recently developed NO-alkyl HALS form a less salt with acidic additives than N-H and N-Me HALS does, because of the lower basicity of NO-alkyl group. An appropriate choice of light stabilizers is necessary to prevent the photo-degradation of polymers effectively.

Keywords: Autoxidation, Ultraviolet Absorbers (UVA), Hindered Amine Light Stabilizers (HALS), Triazine Ultraviolet Absorbers, NO-Alkyl HALS