UV Absorbers and Light Stabilisers

About This Product

Sunlight degrades polymers because ultraviolet photons carry enough energy to break carbon-carbon and carbon-hydrogen bonds, generating the radicals that start photo-oxidation. The visible results are chalking, cracking, gloss loss, yellowing and embrittlement. Two different additive classes address this, and they are commonly used together. UV absorbers work by competitive absorption. Benzotriazoles such as UV-P, UV-326, UV-329 and UV-234 types, and benzophenones such as UV-531, absorb ultraviolet strongly and dissipate it as harmless heat through a reversible internal proton transfer, returning unchanged and ready to absorb again. Their limitation is that they need a certain path length to work, so they protect the bulk of a thick section far better than they protect its surface or a thin film. Hindered amine light stabilisers work differently, and do not absorb ultraviolet at all. They are converted in service into nitroxyl radicals that trap the alkyl radicals produced by photo-oxidation, and are regenerated in the process, so a small amount keeps working over a long period. That regeneration is why HALS outperform absorbers in thin sections and films. Grade selection is by polymer. UV-783 is a synergistic blend for LDPE, LLDPE and HDPE films, tapes and thick sections and for PP fibres and films. UV-944 covers polyolefins, olefin copolymers such as EVA, PP-elastomer blends, polyacetals, polyamides, polyurethanes and flexible and rigid PVC. UV-622 has a low melting range suiting PP, PE, styrenics, unsaturated polyester, acrylic, PVC, plastisols, elastomers, adhesives, sealants and spin finishes. UV-770 is recommended for polypropylene, impact-modified PP, EPDM, polystyrene, IPS, ABS, SAN, ASA and polyurethanes. UV-1130 is a liquid for coatings. UV-360 suits acrylic resins, polyalkylene terephthalates, polycarbonates and high performance plastics. UV-P, UV-329, UV-326 and UV-531 cover styrenics, engineering plastics, PVC, polyolefins and cold-cured polyesters; UV-326 additionally carries wide indirect food approval in polyolefins.