UV stabilizers protect surfaces by stopping the photodegradation process. Hindered amine light stabilizers or HALS are a type of light stabilizer. Unlike UV absorbers, which absorb UV light and prevent it from reaching plastics, HALS has a unique operation involving free radicals and chemical reactions.
When light hits the surface, it sends energy to the atoms in the plastic. These atoms absorb energy, exciting their constituents. UV light also activates HALS to produce nitrogen oxides. This substance absorbs alkyl radicals generated by excited atomic particles. The alkyl groups react with nitrogen oxides to form amino ethers. These ethers then find peroxy radicals in the material. Amino ether destroys peroxy radicals and the reaction product regenerates HALS nitrogen oxides. If these alkyl and peroxy radicals are not neutralized, the material can be damaged by oxidation.
In layman's terms, HALS works by producing products that seek out and "eat" the free radicals released by the material. Without free radicals, the material does not wear out due to photo-oxidation. After the free radicals are consumed, the resulting product produces the ingredients that the HALS needs to work again. Through regeneration, these light stabilizers block UV damage countless times, ensuring their long-term effectiveness.
Because these light stabilizers are self-regenerating, in addition to extending their efficiency, they also have an extremely long lifespan. With the addition of HALS, artificial turf can stay bright and green for a decade or more. Even low concentrations of these light stabilizers have proven effective in protecting materials from photodegradation and thermal abrasion.
However, HALS does have limitations. These light stabilizers are not suitable for any halogen containing polymers such as PVC. Combining them with other additives such as UV absorbers can help improve the performance of HALS in polymers, but their use is not ideal.
