The cause of coating degradation such as discoloration,
delamination, loss of gloss, cracking and chalking is due to the
chromophores, or impurity content, found in the material triggered
by UV light, which is damaging. Therefore, UV absorbers and light
stabilizers are both recommended in order to prevent coating
decomposition. Light stabilizers can be divided into two groups: UV
absorbers (UVA) and the hinder amine light stabilizers (HALS). UVAs
function is to absorb UV light and transform it into heat; HALS is
best known to capture free radicals and prevent material
degradation. What are UVAbsorbers and HALS?
UV Absorbers soak up detrimental UV rays from sunlight,
converting them into heat, which is then dissipated through the
surface of the coating (1). Hindered Amine Light Stabilizers (HALS)
do not absorb radiation; instead they protect the coating resin
from the harmful effect of photochemically-produced free radicals
by neutralizing them, hindering chemical degradation. HALS
regenerate themselves during the neutralization process, so go on
providing protection throughout the lifetime of the coating
(2-4).
