Flame-retardant effects of NH₂-MIL-53(Al) in combination with phosphorus-containing and nitrogen-containing flame retardants on polypropylene

Polypropylene (PP) flammability poses great fire risks for its application. A metal-organic framework (MOF), NH₂-MIL-53(Al), was synthesized and subsequently integrated into PP, the flame-retardant efficacy in conjunction with piperazine pyrophosphate (PAPP) and melamine cyanurate (MCA) was additionally examined. When the total mass fraction of the additives was 25 %, the limiting oxygen index (LOI) of PP composite reached 31.1 %, it also passed the UL-94 test with a V-0 rating. The peak heat release rate (pHRR) and the total heat release rate (THR) was reduced by 88.55 % and 79.75 %, respectively, compared with the pure PP. The char residual char percentage increased to 8.02 %. The Tensile Strength reached 30.1 MPa. The results indicate that adding NH₂-MIL-53(Al) significantly enhanced the flame retardancy and thermal stability of PP composites, without significantly affecting their mechanical properties, which offers a novel potential direction for the advancement of polymer flame retardants (FRs).