A long-term anti-aging and anti-migration nanoscale core-shell flame retardant with supramolecular lock-shell layers for ABS composites

Acrylonitrile-butadiene-styrene (ABS) is widely used but inherently flammable, and conventional flame retardants often suffer from poor compatibility, high migration tendency, or compromised mechanical properties. Herein, a novel nitrogen-phosphorus (N/P) synergistic flame retardant, ammonium 1,3,5-triazine-2,4,6-triyl tri(phosphate) (ATTP), was synthesized, and a nanoscale core-shell flame retardant (NCSFR) with ATTP as the core and crosslinked polyacrylates as the shell was constructed via a supramolecular lock-shell strategy. This unique supramolecular encapsulation not only transforms micron-sized rod-like ATTP into 300–900 nm nanoparticles but also enhances interfacial affinity with ABS. At 40 wt% loading, NCSFR/ABS achieved a limiting oxygen index (LOI) of 24.8% (vs. 17.1% for pure ABS) and superior combustion inhibition (peak heat release rate reduced by 46.2% vs. pure ABS), outperforming ATTP/ABS. TG-IR and SEM confirmed a N/P synergistic biphasic mechanism, that is, gas-phase release of non-flammable gases and phosphorus radicals, and condensed-phase formation of a dense char layer. Benefiting from the supramolecular lock-shell structure, NCSFR/ABS exhibited better mechanical properties than ATTP/ABS at the same 40 wt% loading (tensile strength: 25.3 MPa vs. 21.9 MPa), excellent high-temperature aging resistance (96.77% LOI retention after 100 ℃/2 h aging), and migration resistance (13.33% mass loss after 80 ℃ water immersion, versus 40% for ATTP/ABS). This work highlights the superiority of supramolecular encapsulation in balancing flame retardancy, mechanical performance, and durability for ABS, addressing key bottlenecks of traditional additives. Graphical abstract