Synthesis of a novel N-alkoxyamine containing compound and its application as an effective flame retardant for polypropylene film by quenching free radical

Abstract

A novel N-alkoxyamine containing compound 2,4,6-tri-(1-cyclohexyloxy-4-imino-2,2,6,6-tetramethylpiperidine)-1,3,5-triazine defined as T-TEMPOC was synthesized. Its chemical structure was well characterized and confirmed. The synthesized T-TEMPOC was incorporated into polypropylene (PP) to preparing flame retardant PP film (NOR-PP film). The NOR-PP film with the thickness of 0.2 mm successfully passed UL-94 VTM-0 rating during vertical burning test and its limiting oxygen index value reached 27.3% when 2.0 wt% T-TEMPOC was incorporated, and the heat release rate and total heat release were decreased obviously. The incorporation of T-TEMPOC inhibited the initial thermal degradation of PP on heating and then enhanced the thermal stability of PP film. The NOR-PP film maintained excellent mechanical performance with the introduction of T-TEMPOC. T-TEMPOC could decompose and generate nitroxyl radical, which confirmed by pyrolysis gas chromatography mass spectra measurement. The nitroxyl radical could quench the active free radicals to block the radical chain reaction during combustion, thus suppressed and even extinguished the flame. Moreover, nitroxyl radical was regenerated under the existing of the peroxide. The cyclic process of nitroxyl radical quenching active free radicals and self-regeneration were constructed, which was critical for improving the flame retardant efficiency for PP film. The results might have a promising prospect for flame retardant polymer film.