A bio-based alginate hydrogel with considerable thermoelectric performance, mechanical strength and flame retardancy for ultra-fast and sustained early fire-alarm system

Recently, the widespread utilization of combustible materials has increased the risks associated with building fires. Early fire-warning systems represent a pivotal strategy in mitigating losses incurred from fire incidents and offer considerable potential for the enhancement of fire safety management. This study focuses on the synthesis of bio-based ionic hydrogels, specifically calcium alginate/polyacrylamide/glycerol/lithium bromide (CPG-L X ), as a novel fire sensor. The synthesis was conducted using a one-pot polymerization method combined with solvent exchange techniques. The CPG-L 2 hydrogel exhibits impressive mechanical properties, demonstrating a maximum tensile strength of 1.24 MPa. Moreover, its Seebeck coefficient of 9.31 mV/K indicates a considerable thermoelectric performance. The fire-warning system based on CPG-L 2 is capable of triggering an alarm circuit just within 0.07 s under a heating plate condition of 70 °C, maintaining a warning duration of up to 855 s. Furthermore, it also has considerable flame-retardant, self-healing and water-retention properties. This research indicates the exceptional thermoelectric properties and temperature sensitivity of the bio-based ionic hydrogels, marking a significant advancement in the application of bio-based materials for early fire-warning systems.