Types of Light Stabilizers
There are two types of light stabilizers. One is a UV absorber, which absorbs harmful UV rays to protect the coating. The other is hindered amine light stabilizer, which can capture free radicals and avoid coating degradation.
UV absorbers absorb UV light and compete with chromophores that are part of the polymer backbone to prevent degradation. They are colorless or nearly colorless additives with strong absorption in the ultraviolet part of the spectrum. UV absorbers convert light energy into heat.
Hindered Amine Light Stabilizers (HALS) are used to trap free radicals before subsequent reactions leading to degradation can occur. HALS prevent thermal oxidation. Polymers containing HALS will remain resistant to photodegradation even after running HALS. The explanation for this phenomenon is that the oxidation products of HALS, such as hydroxylamines and aminoethers, can inhibit photodegradation. Both hydroxylamines and aminoethers are capable of trapping peroxide radicals.
