A key role of a bio-based charring-coupling agent in flame retardant and anti-dripping performance of polyamide 6/aluminum diethylphosphinate

In this work, an organophosphorus flame retardant (BHD) was synthesized using 4-formylphenylboronic acid and 1,6-hexanediamine; a charring-coupling agent containing epoxy (DE) was synthesized using daidzein and epichlorohydrin. The BHD and DE were reacted and coated on the surface of aluminum diethylphosphinate (ADP) and the product is identified as BD-ADP. PA6 with 12 wt% BD-ADP achieves a UL-94 V-0 rating and a limiting oxygen index (LOI) value of 30.0 vol%. Substitute 1.0 wt% DE for BD-ADP, PA6-1.0E not only achieves a UL-94 V-0 rating, but also goes out before dripping. The time to ignition of PA6-1.0E is 19 s longer than that of PA6. The flame-retardant mode is the combination of the gas-phase effect of ADP and the condensed-phase effect of DE. In addition, the tensile strength and impact strength of PA6-1.0E are 103.9 MPa and 6.6 kJ/m 2 which are 35.6% and 43.5% more than that of PA6-12A. Both BD coating and DE contribute to a strong interfacial adhesion between ADP and PA6 which improves the mechanical properties. The DE plays a key role in the flame retardancy and mechanical properties of PA6 blends.