Hybridization of the Zinc-Based Organic Framework with Diphenylfenosundinyl Chloride and Its Combination with Hexaphenoxycyclotriphosphazene for Flame Retardancy of Epoxy Resin

In order to further enhance the compatibility and flame retardant efficiency of metal–organic frameworks (IRMOF-3), diphenylphosphinyl chloride was reacted with free –NH2 of IRMOF-3 to prepare an organic–inorganic hybrid (IRMOF-3-P, I-P), and its structure and properties were analyzed by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and thermogravimetric analysis. Then, I-P combined with hexaphenoxycyclotriphosphazene (HPCP) was applied to the flame retardant modification of EP resin, and their synergistic flame retardant effects were studied in detail by the thermal stability, flame retardancy, and mechanical properties of EP composites. The experimental results indicated that I-P particles could be well dispersed in the EP matrix. I-P combined with HPCP could promote the char formation of EP resin, delay ignitions, decrease the release of heat, smoke, CO, and CO2 due to the release of phosphorus free radicals, and have a strong barrier effect, further leading to an increase in its limiting oxygen index to 32.0% and achieving an UL-94 V-0 rating. Finally, EP composites exhibited a good self-extinguishing property. These results proved that the combination of HPCP and I-P had an excellent flame retardant synergistic effect and endowed the EP composite with excellent flame retardancy. In addition, a moderate dose of I-P combined with HPCP can effectively improve the toughness and strength of the epoxy composite.