Photostabilizer

Photostabilizer refers to an additive incorporated into polymers, coatings, cosmetics, or other materials to reduce degradation caused by light, especially ultraviolet (UV) radiation. Light exposure can initiate photooxidation, leading to chain scission, discoloration, embrittlement, and loss of properties. Photostabilizers work by interrupting the photooxidation process through different mechanisms: absorbing harmful radiation, quenching excited states, or scavenging reactive radicals.

The main classes are:

- UV absorbers: organic molecules or inorganic particles that absorb UV light and dissipate it as heat, protecting the host material.

- HALS (hindered amine light stabilizers): amine-based stabilizers that trap radical species formed during oxidation, slowing polymer degradation without necessarily absorbing UV.

- Antioxidants and processing stabilizers: hindered phenols, phosphites, and related compounds that neutralize peroxyl radicals and decompose hydroperoxides.

- Inorganic stabilizers: certain oxides or surface treatments that reduce photocatalytic activity or improve UV resistance.

Applications include plastics used in outdoor products, films and packaging, automotive parts, coatings, textiles, and wood treatments. In each case the choice and concentration of photostabilizer depend on the material, the dominant degradation pathway, processing conditions, optical requirements, and regulatory constraints. Migration, color influence, and heat stability are important considerations, particularly for packaging and food-contact materials.

See also: UV stabilizer, polymer aging, photooxidation.