Bio-based chitosan/amino trimethylene phosphonic acid films enabling highly-efficient intumescent flame retardancy and ultra-fast fire early-warning function

Early fire warning holds immense potential for achieving more efficient fire -safety management. Despite the emergence of numerous fire -alarm sensors in recent years, they display deficiencies in providing prompt and repeatable early detection during fire accidents, thus failing to mitigate potential losses. Herein, we demonstrated a bio-based fire -warning film with chitosan (CS) and amino trimethylene phosphonic acid (ATMP) prepared by an environmental -friendly water evaporation method. The transparency, thermal stability, flame retardancy and fire -warning performances of CS and CS-ATMP films were comprehensively investigated. Remarkably, the inclusion of ATMP results in a significant improvement in the thermal stability and char yield. Moreover, the total heat release value of CS-ATMP-1 film exhibits a remarkable 35.7% reduction compared to that of pure CS film, demonstrating a substantial enhancement in flame retardancy. The thermosensitive properties of CS endow it with fire -warning capabilities. The CS-ATMP-2 film triggers an alarm signal within 0.3 s and the signal maintains for 196.0 s under alcohol flame attack, indicating its high sensitivity and stable alarm signal. Furthermore, the possible flame-retardant and fire -alarm mechanisms are proposed. This bio-based CS-ATMP film with excellent flame-retardant and repeatable early warning capacities manifests promising applications in building fire prevention and detection.