How do UV absorbers, HALS & nickel quenchers work?
UV absorbers & HALS
The composition & molecular weight of a polymer starts to change when it is exposed to shear stress, heat, light, air, water, radiation or mechanical loading. This starts chemical reactions that lead to a modification of the polymers physical & optical properties.
Addivant™ LOWILITE® UV absorbers & HALS are used to avoid the chemical reaction process called photodegradation that takes place when UV radiation from sun or artificial light breaks down the chemical bonds in a polymer, ultimately causing cracking, chalking, color changes & the loss of physical properties.
Addivant™ LOWILITE® UV absorbers function by preferentially absorbing harmful ultraviolet radiation & dissipating it as thermal energy. Addivant™ LOWILITE® HALS (Hindered Amine) Light Stabilizers do not absorb UV radiation, but they form nitroxyl radicals which act as radical scavengers to inhibit degradation of the polymer. Because the HALS are regenerated rather than consumed during the stabilization process & as they are typically high molecular weight stabilizers, they are capable of providing extreme long-term thermal & light stability.
Addivant™ LOWILITE® nickel quenchers are light stabilizers that are able to take over the energy absorbed by the chromophores & dissipate it either as heat or as fluorescent or phosphorescent radiation to prevent degradation. They are mainly used for agricultural film applications (greenhouse & mulch films) where they offer the best balance between UV protection & interaction with pesticides. Addivant™ LOWILITE® nickel quenchers work synergistically with UV absorbers & are often combined to take advantage of this.