The effect of EG on the synergistic flame retardancy of MPP/Co-MOF in polypropylene

Polypropylene (PP) is a widely used thermoplastic resin known for its strong properties, including chemical stability, electrical insulation, and high abrasion resistance. However, its low ignition point and rapid burning rate pose significant fire risks, necessitating the incorporation of flame retardants. In this study, cobalt metal–organic framework (Co-MOF), melamine polyphosphate (MPP), and expandable graphite (EG) were combined to enhance the flame retardancy of PP. The optimal blending ratio was determined, and the results showed that PP/MPP/2 mass% Co-MOF/15 mass% EG composites exhibited superior flame retardancy. These composites achieved a critical oxygen index (LOI) of 28%, a V-0 rating in the UL-94 test, and significantly reduced heat release and smoke production during combustion. The synergistic effect of MPP, Co-MOF, and EG facilitated the formation of a dense, thermally stable carbon layer, which effectively hindered flame propagation and improved fire safety. These findings provide valuable insights for the development of flame-retardant PP materials. Graphical abstract