N-alkoxyamine-containing macromolecular intumescent flame-retardant-decorated ZrP nanosheet and their synergism in flame-retarding polypropylene

High-efficiency macromolecular intumescent flame retardant (MIFR) is urgently demanded but of great challenge. In this work, a novel N -alkoxyamine-containing MIFR-decorated zirconium phosphate (ZrP) nanosheet (denoted as RQMIFR-ZrP) was synthesized and combined with ammonium polyphosphate (APP) to endowed polypropylene (PP) with excellent flame retardancy. With the addition of 6.3 wt% RQMIFR-ZrP and 18.7 wt% APP, PP classed a UL-94 V-0 rating with a high LOI value of 39.5%. Moreover, the peak heat release rate, the total heat release, the peak of CO production, and the peak of CO 2 production of PP/RQMIFR-ZrP/APP decreased by 94.0%, 83.2%, 91.3%, and 91.7%, respectively. It revealed that RQMIFR-ZrP not only generated nitroxyl radicals (NO•) to suppress the chain degradation of PP but also promoted to form high-quality intumescent char layers with the catalytic carbonization and layered barrier effect of ZrP nanosheet, which effectively prevented PP from burning. This work provides a new approach to preparing high-performance flame-retardant polymer.