Preparation of a cobalt metal-organic framework (Co-MOF) and its application as a polypropylene flame retardant by compounding with melamine polyphosphate

A cobalt metal-organic framework (Co-MOF) was successfully prepared, and its combination with melamine polyphosphate (MPP) was studied to enhance the fire retardant properties of polypropylene (PP) composites. The morphology, composition, and structure of PP/MPP/Co-MOF composites were characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The maximum limiting oxygen index of the PP/MPP/Co-MOF composite was 26.8%, which is 49% higher than that of pure PP and its combustion grade reached the V-0 level. When 2 wt% Co-MOF was added, the carbon residue of the composite reached 19.6 wt%, peak heat release rate was significantly reduced, smoke emission was suppressed, fire growth index was significantly reduced, and the fire risk of the composite was effectively reduced. Analysis of the carbon residue showed that aggregated carbon spheres were present on the carbon residue surface of the composite material supplemented with Co-MOF. The generation of carbon spheres effectively prevented the heat exchange and release of combustible gas during the combustion of the composite material, significantly improving the flame retardancy and stability of the material. As a new material, MOF has great innovation and necessity in researching polymer flame retardant. Moreover, the latest composite materials synthesized in this paper contribute to environmental safety to a great extent.