The Improvement of Fire Safety Performance of Polyurethane by Introducing MPP Derivative Functionalized Zeolitic Imidazolate Framework 8 (ZIF–8) Flame Retardant

ABSTRACT A green and environmental‐friendly flame retardant was prepared using halogen‐free zeolitic imidazolate framework‐8 (ZIF‐8) to reduce the flammability and dripping behavior of polyurethane (PU). Mainly comprising phosphorus and nitrogen, the retardant was produced by functionalizing ZIF‐8. First, ZIF‐8 and melamine (MPP) were dissolved in absolute alcohol. Microencapsulation was performed using the –Zn 2+ group of the ZIF‐8 and the –NH 2 of the MPP to form a novel intumescent flame retardant, MPP@ZIF‐8. Furthermore, silanol‐terminated PU (Si‐PU) was formed through the reaction of isophorone diisocyanate (IPDI) with polyol and 3‐aminopropyltriethoxysilane (APTS), and then MPP@ZIF‐8 was introduced into the silanol‐terminated PU to prepare a polymer composite material. The microencapsulation of the ZIF‐8 and MPP was verified with Fourier‐transform infrared spectroscopy, and scanning electron microscopy revealed that, when the additive amount was increased to 40 wt%, high‐temperature combustion produced a thick and dense char layer. Raman spectroscopy further demonstrated that MPP@ZIF‐8 was primarily effective in the condensed phase; with an additive amount of 40 wt%, the I D /I G value decreased from its initial 0.72 to 0.69, indicating substantial damage to the structure and increased formation of the char layer. Furthermore, the ZIF‐8 was an effective flame retardant in both the gas phase and condensed phase by promoting the formation of a continuous and dense char layer and releasing NH 3 and H 2 O gases, which acted as diluents. A cone calorimeter test showed that the total heat release of the MPP@ZIF‐8 composite material decreased from 35.7 to 32.5 MJ/m 2 and that the peak heat release rate also decreased from 910.2 to 591.5 kW/m 2 . These results confirmed the safety improvement of the proposed material during a fire.