Abstract

We co-modified layered double hydroxide (LDH) in water using phosphocreatine (PC) and dodecylphosphoric acid (DPA) to obtain a highly dispersible LDH. Embedding this LDH in epoxy enabled V-0 at 7 wt% and lowered HRR, THR and TSP, attributed to a dense char and PC-DPA synergy. SEM, WAXS, and TGA characterised the structure and thermal behaviour of the functionalised LDHs. These modified LDHs were then loaded into the epoxy resin (EP) to develop flame-retardant nanocomposites. Compared to unmodified LDH (NO3-LDH) and PC-modified LDH (PC-LDH), PC-DPA-LDH showed superior dispersion and compatibility within the epoxy matrix. As a result, PC-DPA-LDH/EP achieved a UL-94 V-0 rating at only 7 wt% loading, while NO3-LDH/EP had no rating, and PC-LDH/EP reached only V-2. Moreover, PC-DPA-LDH/EP demonstrated significant decreases in peak heat release rate (46.4%), total heat release (34.5%), and total smoke production (59.7%) compared with neat EP. These improvements were attributed to the synergistic flame-retardant effects of PC and DPA, as well as to the formation of a compact char layer that effectively insulated the underlying material and suppressed volatile emissions. This work highlights the potential of bio-based, aqueous-synthesised nanohybrids for high-efficiency, eco-friendly flame-retardant epoxy systems.

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