A highly flame-retardant, agile fire-alarming and ultrasensitive cotton fabric-based piezoresistive sensor for intelligent fire system

With the high frequency of fires, multifunctional cotton fabrics with high flame retardancy and agile fire-warning ability are urgently needed. Herein, a newly cotton fabric-based piezoresistive sensor (denoted as CF@A-CNTs/APP) with intelligent fire protection and high sensitivity is proposed, which is composed of amino-functionalized carbon nanotubes (A-CNTs) and ammonium polyphosphate (APP) wrapped on cotton fabric (CF) using layer-by-layer self-assembly. The CF@A-CNTs/APP demonstrated excellent flame retardancy due to the synergistic formation of a dense flame retardant layer on the CF surface by A-CNTs and APP. The char residue of CF@A-CNTs/APP reached 44.0 wt% at 700 °C (nitrogen atmosphere), and the limiting oxygen index of CF@A-CNTs/APP was as high as 37.6%. More importantly, the CF@A-CNTs/APP triggered the fire-alarming system within 2 s. Benefiting from the pattern microstructures of double-layers CF and the high conductivity of A-CNTs, the CF@A-CNTs/APP has exhibited a high sensitivity of 3.8 kPa−1 (0 kPa-16.62 kPa). In view of outstanding flame retardancy, high sensitivity and robustness, the CF@A-CNTs/APPs could be integrated into firefighting suits or electronic skins to monitor the behavioral actions and equipment operating conditions. This work provides a novel strategy for a new generation of CF-based sensors with fire resistance and high sensitivity, and offers new insights into the preparation and application of smart fire-resistant materials in the field of the internet of things.