Fire retardant synergisms between nanometric Fe₂O₃ and aluminum phosphinate in poly(butylene terephthalate)

The pyrolysis and the flame retardancy of poly(butylene terephthalate) (PBT) containing aluminum diethylphosphinate (AlPi) and nanometric Fe 2 O 3 were investigated using thermal analysis, evolved gas analysis (Thermogravimetry‐FTIR), flammability tests (LOI, UL 94), cone calorimeter measurements and chemical analysis of residue (FTIR). AlPi mainly acts as a flame inhibitor in the gas phase, through the release of diethylphosphinic acid. A small amount of Fe 2 O 3 in PBT promotes the formation of a carbonaceous char in the condensed phase. The combination of 5 and 8 wt% AlPi, respectively, with 2 wt% metal oxides achieves V‐0 classification in the UL 94 test thanks to complementary action mechanisms. Using PBT/metal oxide nanocomposites shows a significant increase in the flame retardancy efficiency of AlPi in PBT and thus opens the route to surprisingly sufficient additive contents as low as 7 wt%.