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

Abstract

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.