The working principle of UV absorbers is to protect materials from UV damage by absorbing high-energy UV rays and converting them into harmless heat or other forms of low-energy radiation. UV absorber molecules contain specific structures, such as conjugated π electron systems and structures with mobile hydrogen atoms, which can absorb UV rays and trigger electron transitions and thermal vibrations within the molecule, ultimately releasing the absorbed energy as heat.
Working principles of different types of UV absorbers
Benzophenones: The ketone group and hydroxyl group in this type of absorber molecule can form an internal hydrogen bond to form a chelate ring. After absorbing UV rays, the chelate ring opens and converts the energy of UV light into heat and releases it. In addition, the carbonyl group in the molecule will be excited by the absorbed UV energy, resulting in tautomerism and further consuming energy.
Salicylate: This type of absorber will undergo molecular rearrangement under UV irradiation to form a benzophenone structure with strong UV absorption ability, thereby enhancing its absorption effect.
Benzotriazoles: This type of absorber has a wide range of UV absorption, can strongly absorb 310~385nm UV light, and convert it into heat energy for release.
Application fields of UV absorbers
UV absorbers are widely used in various fields due to their unique properties:
Plastics: Prevent plastics from photodecomposition under long-term exposure to sunlight. For example, UV absorbers can be added to a variety of plastics such as polyvinyl chloride, polyvinylidene chloride, polymethyl methacrylate, unsaturated polyester, ABS resin and cellulose resin to improve their light stability.
Rubber: Used for photostabilization of synthetic rubber to extend the service life of rubber products.
Coatings: Protect coatings from UV damage and improve coating durability and light stability.
Ink: Prevent ink from fading under light and maintain the brightness and durability of ink.
Textiles, leather, paper: Improve the light stability and weather resistance of these materials.
Specific application examples of different types of UV absorbers
Benzophenones: widely used in polyethylene, polypropylene, polyvinyl chloride, ABS, polystyrene, polyamide, epoxy resin, polyurethane and other polymers as well as textile finishing. This type of absorber hardly absorbs visible light, has good compatibility with high molecular polymers, and has good light and heat stability.
Benzotriazoles: have long-lasting performance and are widely used in industrial coatings, adhesives, unsaturated polyesters, PVC, polycarbonate, polyamide and other materials. This type of absorber hardly absorbs visible light above 400nm, the product will not be discolored, and has good stability.