Flame retardant performance of PA 6/ADP composites

Diethyl-phosphate aluminum(ADP) was mixed with polyamide 6(PA 6) by the twin screw extruder to prepare PA 6/ADP composites. The thermal and mechanical properties of PA6/ADP composites as well as flammability are characterized by differential scanning calorimeter, UL-94 burning rating, limiting oxygen index (LOI) and cone calorimeter test respectively. The results show that the addition of ADP helps to improve the glass transition temperature of the composites; while the mechanical properties of PA 6 drops slightly; the LOI value of PA 6 achieves 33.5% when ADP is 22 wt% compared with that of 26.7% of pure PA 6, and UL-94 (1.6 mm) can reach V-0 rating without melting and dripping. The peak heat release rate (PHRR) decreases from 1200 kW/m² to 500 kW/m2 in the 22 wt% ADP loading. The composite produces dense char residue after burning, which can prevent the heat and oxygen from transferring to PA6 matrix.