Thermal insulating and fire-retarding behavior of treated cotton fabrics with a novel high water-retaining hydrogel used in thermal protective clothing

Hydrogel-born fire resistance materials have attracted great attention due to their flame retardance and environmental friendliness. In this work, a facile strategy is presented to prepare a novel hydrogel–cotton fabric laminate with excellent thermal insulation and fire-retarding performance. The hydrogel–fabric laminates exhibited outstanding flame retardant behavior. The flame-retardant mechanism of this system was mainly due to the absorption of a large amount of energy as the water is heated and evaporated in the hydrogel layer. To increase the water retention capacity of the fire-resistant hydrogel, highly hydratable salt (CaCl2) was incorporated into the fire-resistant composite hydrogel composed of poly(N-isopropylacrylamide) (PNIPAAm)/sodium alginate (SA) to prolong water retention time. Here in this work, we aimed to investigate the effect of CaCl2 concentration on water retention capacity, fire-resistant and thermal insulating properties of hydrogel–cotton fabric laminates. Results indicated that the presence of hydratable salt successfully prolonged the water retention time and provided superior fire retardance property over traditional hydrogel. In additional, infrared imaging and vertical flammability test results confirmed that hydrogel–fabric laminates were capable of sustaining 1200 °C for 30 min without the cotton fabric layer burning, whereas natural cotton fabric was completely burned after 12 s. Finally, the hydrogel–cotton fabric laminates exhibited remarkable antibacterial activity against Staphylococcus aureus and Escherichia coli due to incorporated silver nanoparticles in hydrogels, and the bacteriostatic rates both exceeded 96%. The preparation of this hydrogel-born fire resistance materials is facile and can extended the period of protective time as fire resistant clothing for the firefighters.