Synergistic flame retardancy of <scp>MIL</scp> ‐ <scp>88B</scp> ‐Fe metal–organic framework with aluminum diethyl hypophosphite in epoxy resin

Abstract 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 PET waste‐derived MIL‐88B‐Fe showed synergistic flame retardancy with ADP. 4% MIL‐88B‐Fe and ADP at a 1:19 weight ratio in EP reached a UL‐94 V‐0 rating. MIL‐88B‐Fe/ADP flame retardant hardly decreased the EP mechanical properties.