Light Stabilizers Hindered amine light stabilizers were developed as photo-stabilizers and/or metal deactivators to use in plastic industry. HALS additives hardly absorb UV light but act most likely as radical scavengers and hydroperoxide decomposers to inhibit or slow down the photochemical degradation of the polymer. HALS additives such as UV- 770, UV-944 and UV-622 are light stabilizers agents, because of their chemical structure with various molecular weight distribution, contribute significantly to the long term heat stability of polymer resins. Hindered amine light stabilizers were developed as photo-stabilizers and/or metal deactivators to use in plastic industry.