Fuente: Journal of applied polymer Lugar: RESEARCH ARTICLE Schematic illustration of the synergistic flame-retrardant mechanism of ADP and HAPCP in PA6/GF composite.

ABSTRACT
To improve the flame retardancy of glass fiber (GF)-reinforced polyamide 6 (PA6/GF) composites and alleviate the “candlewick effect” caused by GF, this work synthesized hexa (4-aldehyde phenoxy) cyclotriphosphazene (HAPCP) via the reaction of hexachlorocyclotriphosphazene (HCCP) and p-hydroxybenzaldehyde (PHB). Subsequently, HAPCP was combined with aluminum diethylphosphinate (ADP) to fabricate glass fiber-reinforced polyamide 6 (PA6/GF) composites. The structural characterization of HAPCP was conducted, and the thermal stability, flame retardancy, and mechanical properties of PA6/GF composites were systematically investigated. The results indicated that compared with neat PA6/GF, the limiting oxygen index (LOI) of PA/1H/9ADP (adding 1 wt% HAPCP and 9 wt% ADP in PA6/GF) increased from 21.7% to 34.4%, and the UL-94 rating achieved V-0, with no melt droplets during combustion. The peak heat release (PHRR) and the total heat release (THR) respectively decreased by 51.2% and 29.4%, and the fire performance index (FPI) increased by 107.4%, demonstrating significantly enhanced flame retardancy. HAPCP existed a strong synergistic effect with ADP, promoting the formation of a continuous and compact protective layer during combustion, and generating non-combustible gases that reduce the concentration of flammable species. This effectively mitigated the “candlewick effect” and improved the overall flame retardant performance of PA6/GF composites.