Application of aluminum diethyl hypophosphite, iron-based metal organic framework-NH₂-MIL-53(Fe), and expandable graphite complexes as flame retardants for high-density polyethylene

High-density polyethylene (HDPE) composites are made by melt blending HDPE with MIL-53(Fe), amino-functionalized NH₂-MIL-53(Fe), aluminum diethyl hypophosphite (ADP), and expandable graphite (EG). The experimental disclosed showed that the aminated NH₂-MIL-53(Fe) could improve residual carbon quality and exert a better flame retardant effect than MIL-53(Fe). When 25 wt% of EG/ADP/NH₂-MIL-53(Fe) was added and the ratio of EG to ADP/ NH₂-MIL-53(Fe) was 1:1, HDPE/EG/ADP/NH₂-MIL-53(Fe) composites could achieve a limiting oxygen index of 31.1 %, which passed UL-94 testing and was rated V-0. This results in a considerable improvement in flame retardant efficiency as the peak heat release rate was lowered by 83.4 % and the total heat release was reduced by 35.8 % when compared to the pure HDPE material. Therefore, NH₂-MIL-53(Fe)/ADP/EG synergistic flame retardancy can lead to high flame retardancy efficiency in HDPE. This provided a new potential direction for the preparation of highly efficient flame retardants.