Light stabilizers are essential additives that inhibit photo-oxidation and photo-aging of polymeric materials such as plastics, coatings and fibers, preventing deterioration of their appearance and mechanical properties caused by ultraviolet (UV) radiation. They are mainly classified into four categories based on their action mechanisms, each with distinct characteristics and performance advantages.

UV absorbers (UVA) are the most widely used type in industry, mainly including benzophenones, benzotriazoles and triazines. Their core characteristic is to selectively absorb harmful UV light (290-410nm) and convert it into harmless heat energy. They have good compatibility with most polymers and do not affect material transparency, but their effectiveness is limited by the Lambert-Beer law, making them less suitable for thick products.

Hindered Amine Light Stabilizers (HALS), as free radical scavengers, are highly efficient and widely used. They capture free radicals generated during photo-oxidation to terminate the auto-oxidation chain reaction, with excellent long-term stability even at low concentrations. Polymeric HALS such as Chimassorb® 944 perform better than monomeric ones in gloss and tensile strength retention, but they are alkaline and may react with acidic substrates. Light screeners act as a physical barrier between polymers and UV radiation, reflecting or blocking UV light from penetrating the material interior. Common varieties include carbon black and titanium dioxide, featuring low cost and good protection effects, but they have coloring and light-shielding properties, only suitable for opaque products.

Quenchers, mainly organic nickel complexes, dissipate the excited energy of chromophores in polymers as heat or fluorescence. They are effective for thin films and fibers but have drawbacks such as high toxicity and discoloration at high temperatures, gradually being replaced by low-toxic alternatives. In practical applications, combining UVA and HALS can achieve a synergistic effect, significantly improving material weather resistance.