Flame-retardant and fire-warning cotton composite fabrics based on the thermoelectric effect of polypyyrole doped with P-toluenesulfonic acid

Recently, many efforts have been devoted to studying early-stage fire-warning materials (EFWMs). Among those, thermoelectric effect-based EFWM (TE-EFWMs) are particularly attractive because they are self-powered and intrinsically sensitive to temperature. However, none of the reported fire-warning response times of TE-EFWMs can reach 1.0 s. Herein, flame-retardant composite cotton fabrics with speedy and repeatable fire warning function (denoted as CF-TE-FR) were constructed by in-situ polymerized polypyrrole (PPy) doped with P-toluenesulfonic acid (PTSA) and a flame retardant composite layer composed of sodium montmorillonite (MMT) and ammonium polyphosphate (APP). The fire warning performance of CF-TE-FR was effectively enhanced through PTSA doping, and the fire warning response time was shortened with an increasing concentration of PTSA. The fire warning indicator could be triggered as fast as 0.8 s when the molar ratio of PTSA to pyrrole monomer reached 1:3. Meanwhile, all the CF-TE-FR samples could release the fire-warning signals repeatedly. This work proposes a facile approach to the fabrication and application of organic thermoelectric polymer-based materials with ultrafast fire-warning response, repeatable fire-warning capability, and excellent flame retardancy. Graphical abstract Flame-retardant cotton fabrics based on the thermoelectric effect of polypyrrole demonstrate speedy and repeatable fire warning function.