Photo-Oxidative Stabilization Effect of a Reactive Hindered Amine on Monomer Casting Nylon-6

Monomer casting (MC) nylon-6 was polymerically modified by grafting 4-amino-2,2,6,6-tetramethylniperidine (TEMP), as a reactive hindered amine, onto its chain so as to improve the compatibility and stability of the stabilizer in the polymer matrix. The long-term aging of MC nylon-6 under UV irradiation indicated that the grafted sample of MC nylon-6 had lower gel content than that of the pure sample, and only a slow change in the reduced viscosity was observed. The carboxyl concentration of the grafted sample was lower than that of the pure sample, and its terminal amine group concentration was relatively higher during the whole aging process, presenting a more stable chemical structure. The delayed oxidation exothermic peak and increase of oxidation induction time (OIT) suggested that the grafted TMEP was stable in the matrix of nylon-6 after long-term UV aging. Decreasing crystallization ability after aging was observed for the pure sample of MC nylon-6, while a relatively stable crystallization behavior was observed for the grafted samples, indicating that TEMP can inhibit the structural change of MC nylon-6 during UV irradiation.