Thermal-oxidative stabilization effect of reactive-hindered amine on monomer casting nylon-6

Abstract

Monomer casting (MC) nylon-6 was a polymeric modified by grafting 4-amion-2,2,6,6-tetramentylniperidine (TEMP) as reactive-hindered amine onto its chain so as to improve the compatibility and stability of the stabilizer in the polymer matrix. The structure of the reactive stabilizer was confirmed by Fourier transform infrared and proton nuclear magnetic resonance spectroscopic analyses. The effect of TEMP on the thermal stability of MC nylon-6 was studied. It was found that with the increase in TEMP dosage, the thermal weight loss of the samples first decreased and then increased and the preferred dosage of TEMP was about 0.2 mol%. The residual weight percentage ( R) of all the samples decreased with heating time, and it does much more slowly for the grafting sample than that of pure one. The thermal degradation characteristic temperatures of MC nylon-6 were improved by grafting TEMP. The long-term aging of MC nylon-6 indicated that the carboxylic acid concentration of the grafting sample was lower than that of the pure sample, and its end amine group concentration was relatively higher during the whole aging process, presenting more stable chemical structure. Ultraviolet absorption and gel content of MC nylon-6 were also reduced by grafting TEMP. The crystallinity ( Xc) of MC nylon-6 increased, and the crystallization growth rate and melt temperature ( Tm) decreased with aging time, resulting from the annealing process at high temperature and the small molecular products during aging.