Facile Construction of a Flexible Film with Ultrahigh Thermal Conductivity and Excellent Flame Retardancy for a Smart Fire Alarm

Design and development of intelligent fire warning materials with rapid response capabilities has always been an urgent need for the safety of many flammable materials in their applications. Herein, an aminated black phosphorene (BP-NH2) prepared by ball milling was employed to connect with graphene oxide (GO) via covalent bonds to fabricate a flexible film with ultrahigh thermal conductivity and remarkable flame retardancy. The thermal diffusivity of the RPNG 20 film is as high as 1496.87 ± 51.11 mm2 s–1, and its thermal conductivity is also up to 1085.74 ± 37.08 W m–1 K–1, which is in full agreement with the theoretical calculation value (1086.9 ± 59.1 W m–1 K–1) of the multilayer graphene nanosheets reported in the previous literature. The effective medium theoretical calculations show that the interface thermal resistance has been reduced to 1/367 of that of pure graphene, which promotes the heat transfer of phonons. Simultaneously, it displays excellent flame-retardant properties. The peak of the heat release rate (PHRR) value is only 12.46 W g–1, resulting in a 96.57% decrease compared with that of the pure GO film (363.17 W g–1), which is attributed to the formation of an intumescent flame-retardant system. More importantly, when encountering a flame attack, the unreduced flexible film demonstrates an extremely fast fire alarm response capability of less than 1 s and can continue to work after leaving the fire, which is ascribed to the high degree of carbonization after contacting with fire. This covalent linkage strategy provides a new thought for the preparation of multifunctional films to improve the fire prevention and protection response capabilities in the smart fire alarm device.