Flame-Retardant and Fire-Sensing Packaging Papers Enabled by Diffusion-Driven Self-Assembly of Graphene Oxide and Branched Polyethyleneimine Coatings

Paper has gained popularity as a packaging material due to its reduced environmental impact compared with non-degradable alternatives. However, its flammability poses safety risks, prompting research on enhancing its flame retardancy. This work introduces a diffusion-driven self-assembly strategy (DDSAS) to create a functional graphene oxide (GO) coating on various packaging papers. DDSAS involves infiltrating the paper’s cellulose microfiber network with branched polyethyleneimine (b-PEI), which binds firmly to cellulose microfibers. Electrostatic interactions between GO and b-PEI then drive GO assembly into a densely stacked, layered structure on the paper surface. This GO structure provides a physical barrier against flames and generates incombustible gases (CO2, H2O, NO2, and NO) when heated, diluting the surrounding oxygen concentration and acting as a heat insulation layer. These factors increase the flame retardancy of treated papers ten-fold. Additionally, the gradual reduction of GO upon heating forms reduced graphene oxide (rGO) on the paper, significantly increasing its electrical conductivity. As a result, the flame-retardant papers not only prevent the fire from spreading but can also act as fire sensors by triggering an alarm signal at the early stages of contact with fire. In summary, this work offers a rational strategy for designing and manufacturing flame-retardant paper packaging materials.