Graphitic nanotubes confined with Ni nanocrystals: Artificial armor for ammonium polyphosphate towards fire-safe epoxy composite

With the ever-growing usages of epoxy resin (EP) in versatile aspects, its high fire hazard comes to prominence. How to improve the flame retardancy of EP at the least cost has been hotspot. In this context, we have constructed an artificial armor, namely N doped graphitic nanotubes confined with nickel nanoparticles (NGNTs@Ni), on the surface of ammonium polyphosphate (APP). Here, the ratios of NGNTs@Ni and APP are fixed at 1:9, 2:8, 3:7, acquiring the flame retardants of 1NGNTs@Ni/9APP, 2NGNTs@Ni/8APP, 3NGNTs@Ni/7APP. Compared with APP, 1NGNTs@Ni/9APP induces the superior inhibitions in heat, smoke and toxic gas releases. Concretely, the using of 15 wt% APP leads to reductions of 65.1 %, 22.8 %, 57.7 %, 40.1 % in peak heat release rate (PHRR), peak CO production rate (PCOPR), peak CO₂ production rate (PCO₂PR), peak smoke production rate (PSPR). By using 10 wt% 1NGNTs@Ni/9APP, the reductions in PHRR, PCOPR, PCO₂PR, PSPR reach 75.6 %, 49.2 %, 70.4 %, 60.4 %. As anticipated, the high loading of APP triggers the decreases in mechanical properties while the using of modified APP results in the promotion in mechanical performances. In short, this work can provide inspirations for the facile design of APP based flame retardant, reducing its dosage and improving its flame retardation efficiency.