Synergistic effects of novolac-based char former with magnesium hydroxide in flame retardant polyamide-6

In this paper, a novel synergistic flame retardant system containing magnesium hydroxide (MH) and methyl-blocked novolac (MBN) synthesized by Williamson ether route, were used for the flame retardance of polyamide-6 (PA6). The investigations showed that the thermal oxidative stability of MBN was obviously enhanced in the presence of MH compared with virgin novolac due to the decrease of phenol hydroxide groups subjected to be oxidized. It proved that MBN plays double roles: on the one hand, it remarkably promotes char formation and effectively eliminates the melt drips of PA6, therefore endows the materials with good flame retardancy; on the other hand, it also serves as an efficient lubricant and compatibilizer between MH and PA6, leading to the great improvement of the processability, as well as finer dispersion of MH in matrix, thus the flame retardant PA6 with good comprehensive performance can be obtained.