Abstract:

Objective To address the issue of indoor fire alarms caused by flammable cotton fabrics, MoS₂/MXene flame retardant gas sensitive cotton fabrics were prepared with dual functions of active early warning response and passive flame retardant protection. It is significant for protecting personal and property safety by detecting characteristic CO₂ gas in the early stages of a fire and preventing the spread of flames.

Method Phytic acid-doped polypyrrole modified cotton fabrics were prepared using in-situ polymerization with phytic acid as dopant. Meanwhile, MoS₂/MXene hybrid nanomaterials were synthesized via a hydrothermal method and then assembled onto the modified fabrics by impregnation method to obtain CO₂-responsive flame retardant cotton fabrics. The thermal stability, flame retardant performance and CO₂ gas sensitivity were evaluated by thermogravimetric analysis, an FTT micro calorimeter and a digit multimeter, respectively.

Results MoS₂/MXene flame retardant gas sensitive cotton fabrics were successfully prepared. The surface of the pure cotton fabric was initially smooth, but after modification with phytic acid-doped polypyrrole, it became rough and covered with numerous particles. This change is due to the in-situ synthesis of the doped polypyrrole particles adhering to the cotton fabric. After dipping, the surface of flame-retardant cotton fabric became even rougher with regular folds, indicating successful adsorption of the MoS₂/MXene nano-hybrid material. The MoS₂/MXene flame retardant coating reduced the maximum weight loss rate of cotton fabric by 55.2% and increased the residual carbon content from 9.6% to 21.7%, enhancing thermal stability. Additionally, the coating decreased the peak heat release rate and total heat release by 83.5% and 68.7%, respectively, from 235.8 W/g and 26.7 kJ/g to 38.9 W/g and 8.0 kJ/g. This improvement is attributed to the P-N synergistic flame retardant effect of the doped polypyrrole and the barrier effect of MoS₂/MXene. The fabrics also exhibited high sensitivity to CO₂ gas, with a significantly higher resistance change rate compared to fabrics treated only with MoS₂ or MXene. At a CO₂ concentration of 180 mg/m³, the resistance change rate was as high as 49.9%, allowing for early detection of CO₂ changes during the initial stages of a fire. The presence of P-N heterojunctions in the MoS₂/MXene flame retardant gas sensitive cotton fabrics increased the concentration and migration rate of carriers in the channel, thereby enhancing the sensitivity of MoS₂/MXene flame retardant gas sensitive cotton fabrics to CO₂ gas. In addition, MoS₂/MXene flame retardant gas sensitive cotton fabrics provide more adsorption sites for CO₂ gas, further improving the sensitivity.

Conclusion MoS₂/MXene flame retardant gas sensitive cotton fabrics were successfully synthesized, demonstrating dual functionality of active early warning response and passive flame retardant protection. Compared to pure cotton fabrics, the MoS₂/MXene flame retardant gas sensitive cotton fabrics show significant improved flame retardant efficiency, with an 83.5% reduction in the peak heat release rate and a 68.7% reduction in total heat release. This performance is mainly due to the P-N synergistic flame retardant effect of phytate-doped polypyrrole and the barrier effect of MoS₂/MXene. In addition, MoS₂/MXene flame retardant gas sensitive cotton fabrics exhibit high sensitivity to CO₂gas, capable of monitoring sudden change of CO₂ at the initial stage of a fire. This study shines a new light on fire prevention and control.

Key words: MoS₂, MXene, heterogeneous structure, flame retardant early warning, gas-sensitive mechanism, flame retardant fabric, functional textiles