Environmentally Benign Flame Retardant Polyamide‐6 Filament for Additive Manufacturing

The engineering applications of thermoplastic 3D printing filaments are currently limited by their inherent flammability, especially in fields such as automotive and aerospace, which require high standards for material safety. Polyamide-6 (PA6) is of particular interest for additive manufacturing but is a very flammable thermoplastic known to spread fires due to its aggressive melt-dripping. A flame retardant (FR) composite filament composed of PA6, ammonium polyphosphate, and aluminum phosphate is shown to be printable under identical conditions to commercially available PA6. Calorimetry measurements reveal that the composite filament generates a 7000% increase in char yield, along with 47% and 31% decreases in peak heat release rate and total heat release, respectively. Additionally, open flame testing demonstrates a significantly reduced capacity for this filament to spread fire to other nearby combustible materials. This unique FR additive system represents an important step toward improving the safety and utility of 3D printed parts.