APP with aluminium phosphate provided fire performance compatible with PA6 3-D printing. 20% APP (ammonium polyphosphate) and 10% aluminium phosphate (AlPO4) was compounded/extruded at 235°C into polyamide-6 for 3D-printing filaments (FFF additive manufacturing: Fused Filament Fabrication). T-shaped parts, c. 4 cm, were then printed, with an internal lattice structure (not solid filled). Such hollow-structure 3D-printed items are potentially highly flammable. The PIN FR PA6 filaments could be printed identically to neat PA6. Compared to neat PA6, the PIN FR PA6 showed much higher char yield, 47% and 31% lower peak and total heat release, and reduced melt dripping. The authors conclude that this PIN FR combination can significantly improve the fire safety of 3D-printed materials.
“Environmentally Benign Flame Retardant Polyamide-6 Filament for Additive Manufacturing”, T. Kolibaba et al., Macromol. Mater. Eng. 2021, 2100245 https://doi.org/10.1002/mame.202100245