Effects of iron-based metal–organic framework-MIL-53(Fe) and phosphorus-based flame retardants on the flame retardancy of high-density polyethylene

An iron-based metal–organic framework, MIL-53(Fe), was synthesized and added as a synergist to high-density polyethylene (HDPE), and its flame-retardant effect with aluminum diethyl hypophosphite (ADP) and aluminum hypophosphite (AHP) in HDPE was investigated to further improve the flame-retardant efficiency. FTIR results showed that the ADP, AHP, and MIL-53(Fe) were successfully incorporated into the HDPE. The LOI of HDPE-3 and HDPE-7 with 0.75 mass% MIL-53(Fe) was 48.9% and 34.8% higher than that of the pure sample. The combustion grades reached V-0 and V-1. HDPE/MIL-53(Fe)/ADP exhibited more superior flame-retardant properties than HDPE/MIL-53(Fe)/AHP. A synergistic effect between ADP and both AHP and MIL-53(Fe) changes the decomposition process of HDPE. In addition, the FGI value of the composites decreased after the addition of MIL-53(Fe). MIL-53(Fe) enhances the thermal stability of HDPE composites, and improves the quality of the char residue. Experimental results show that MIL-53(Fe) can be used as a flame retardant and is a novel material in polymer flame-retardant research. The new synthetic material shown here may contribute to environmental safety.