A sustainable alginate-based multifunctional porous material with integrated thermal barrier and reversible fire warning for enhanced building protection.

The need for innovative bio-based building material development that solves excessive energy consumption and environmental sustainability and enables thermal barrier with sensitive early fire warnings is urgent. This study focuses on developing a sustainable multifunctional SNAP (sodium alginate/nickel oxide/ammonium polyphosphate/polypyrrole) porous material, fabricated by incorporating sodium alginate (NaAlg) as the primary structural matrix, ammonium polyphosphate (APP) as a flame retardant, nickel oxide (NiO) for temperature sensing and enhanced flame retardancy, and polypyrrole (PPy) to improve electrical conductivity for fire warning functionality. The inclusion of APP, NiO, and PPy significantly improved the limiting oxygen index to 48.7 %, and a robust char layer during flame exposure provided effective thermal barrier and self-extinguishing properties. The porous material exhibited thermal conductivity of 0.076 W·m-1·K-1. The synergistic integration of NiO and PPy enhanced temperature sensing and electrical conductivity, enabling ultrafast (0.9 s) flame detection and a stable fire warning period of 227 s (under continuous exposure) with reversible warning characteristics. Post-crosslinking with Ca2+ ion improved mechanical strength (0.32 MPa) and maintained stability up to 48 h of immersion in deionized water. This innovative, environmentally friendly composite material holds significant promise in advanced building materials where high fire safety and early warning systems are critical.