Flame-retardant polybenzoxazine nanocomposites with suppressed smoke and toxic gas emission enabled by copper-embedded laser-induced graphene

The development of polymeric materials that integrate both flame retardancy and smoke suppression is crucial for upgrading fire protection level. Traditional flame-retardant methods generally introduce special elements or form intumescent carbon, which exacerbate the release of toxic smoke. Herein, a nanocomposite derived from daidzein-based benzoxazines (Dz-f) and nano-smoke suppressants (Cu@LIG) is reported, which enables the formation of a dense char barrier and facilitates the complete oxidation of carbon monoxide during combustion. Specifically, Cu@LIG features copper-embedded graphene structure was synthesized via laser-induced graphene technology using a polybenzoxazine precursor containing copper(II) acetylacetonate. This material was incorporated into Dz-f matrix via solvent-assisted molding to form a nanocomposite. With only 0.75 wt% Cu@LIG, the composite maintained good thermal stability, mechanical property, and fire safety, while significantly improving smoke suppression performances. It not only achieved a UL-94 V-0 rating and reduced total heat release from 65.4 to 60.9 MJ/m 2 . Furthermore, the maximum smoke density also decreased from 178.7 to 104.9, and the CO production was lowered by 16.3%. Mechanistic studies indicate that the copper species in Cu@LIG catalyze the oxidation of CO to CO 2 and participate in forming a dense char layer in the condensed phase. This work provides an effective strategy for balancing flame retardancy and smoke suppression and offers insights for designing advanced nano smoke suppressants.