Hindered amine light stabilizer peroxy radicals

E.N. Step, J. Turro, M.E. Gande, andP.P. Klemchuck, Mechanism of polymer stabilization by hindered-amine light stabilizers (HALS). Model investigations of the interaction of peroxy radicals with HALS amines and amino ethers, Macromolecules 1994, 27, 2529-2539. 

Obviously, in a PA melt, phenols undergo reactions and the reaction products are unable to react with the amide peroxy radical. On the other hand, antioxidants of the hindered amine light stabilizer type interrupt the oxidation reaction of PA6 after an induction period. During this induction period, they are oxidized to the N-oxyl form, which is essentially reactive... 

Hindered amines are effective in preventing UV degradation. They are generally thought of as light stabilizers rather than as antioxidants. Hindered amines work by trapping both alkyl and peroxy radicals. 

---