In Situ Cross-Linking\nReinforced Cellulose Aerogel\nFibers for Thermal Insulation and Multifunctional Applications

Cellulose aerogel fibers (CAFs) which have a porous nanonetwork\nand fiber geometry are promising candidates for thermal insulation\nor flexible devices due to their excellent thermophysical properties,\nrenewability, and cost-effectiveness. However, their weak skeletal\nstructure, low mechanical strength, combustibility, and poor moisture\nresistance remain significant barriers to their commercial viability.\nThe establishment of physical and chemical cross-links is a potential\nstrategy to enhance the strength, toughness, and overall performance\nof aerogels. In this work, interconnected networks of cellulose-based\naerogel fibers are fabricated through continuous coagulation spinning\nand modified with the addition of 4,4′-methylene diphenyl diisocyanate\n(MDI) as the cross-linker. The CAFs modified with 1.5 wt % of MDI\nhave good tensile strength (27.7 MPa), an ultrahigh Young’s\nmodulus (735 MPa), and excellent bending resistance even after they\nare knotted or looped for the tensile tests. The fabric made with\nMDI-modified CAFs is lightweight and flexible and has humidity insensitivity,\nwith a better thermal conductivity of 0.09 in a 98% humidity environment\ncompared with pristine CAFs. Significantly, the insulation of this\nfabric is almost the same as cotton wadding, yet only 1/5 of its thickness\n(RH = 50–60%). In addition, different functionalized aerogel\nfibers have been fabricated, such as those that are colored, antibacterial,\nand flame-retardant. The study shows the huge potential of cellulose-based\naerogel fibers and textiles in producing the next generation of biomass-based\nhigh-performance thermal insulating devices.