UV stabilizers protect a surface through arresting the photodegradation process. Hindered amine light stabilizers, or HALS, are a type of light stabilizer. Unlike UV absorbers that take in the ultraviolet light and keep it from reaching the plastic, HALS have a distinct operation that involves free radicals and chemical reactions.
When light hits a surface, it sends energy to the atoms in the plastic. These atoms absorb the energy, which excites their components. The UV light also activates the HALS to create nitroxide. This substance takes in alkyl radicals the excited atomic particles produce. The alkyl reacts with the nitroxide to form amino ethers. These ethers then find peroxyl radicals in the material. The amino ethers destroy the peroxyl radicals, and the products of the reaction regenerate the HALS nitroxides. Without neutralizing these alkyl and peroxyl radicals, the material would experience damage through oxidation.
In layman's terms, HALS work by producing products that look for and "eat" the free radicals released from the material. Without the free radicals, the material does not wear down from photooxidation. After consuming the free radicals, the resulting products produce the components needed by the HALS to work again. By regenerating, these light stabilizers can stop UV damage innumerable times, ensuring their long-term effectiveness.
Because these light stabilizers regenerate themselves, they have extremely long lives in addition to extended efficiency. With the addition of HALS, artificial turf can remain bright and green for a decade or longer. Even low concentrations of these light stabilizers prove effective at keeping the material protected from photodegradation and thermal wear.
HALS do have limitations, however. These light stabilizers do not work well with any polymers containing halogen, such as PVC. Combining them with other additives such as UV absorbers can help improve the performance of HALS in polymers they do not have ideal use with.
