Synergistic flame retardancy of MIL-88B-Fe metal-organic framework with aluminum diethyl hypophosphite in epoxy resin

Four metal-organic frameworks (MOFs), namely MIL-88B-Fe, MIL-53-Fe, Co-MOF, and Ni-MOF, were successfully prepared using polyethylene terephthalate (PET) waste as the raw material. The structure and morphology of the prepared MOFs were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Subsequently, the synergistic flame retardancy of these MOFs with aluminum diethylphosphinate (ADP) in epoxy resin (EP) was compared. The prepared MOFs, in particular MIL-88B-Fe, exhibited significant synergistic flame retardancy when used in combination with ADP. When the addition amount of MIL-88B-Fe and ADP in EP was 4% with the MIL-88B-Fe to ADP weight ratio at 1:19, the prepared flame-retardant EP, EP/Fe88B-ADP-2:38, successfully achieved a high limiting oxygen index (LOI) value of 34.2%. Thermogravimetric analysis (TGA) results indicated that the residual carbon amount in EP/Fe88B-ADP-2:38 increased by approximately 6.6% compared to pure EP. Additionally, the peak heat release rate (PHRR) of EP/Fe88B-ADP-2:38 decreased by 30.2% compared to pure EP. EP/Fe88B-ADP-2:38 also demonstrated excellent smoke suppression, with a 16.5% decrease in total smoke production (TSP) compared to EP. These studies have provided new insights into the efficient utilization of PET waste. The synergistic flame retardant, composed of PET waste-derived MIL-88B-Fe and ADP, can enhance the flame retardancy of EP while preserving EP's mechanical properties. Highlights center dot PET waste-derived MIL-88B-Fe showed synergistic flame retardancy with ADP. center dot 4% MIL-88B-Fe and ADP at a 1:19 weight ratio in EP reached a UL-94 V-0 rating. center dot MIL-88B-Fe/ADP flame retardant hardly decreased the EP mechanical properties.