In Situ Cross-Linking Reinforced Cellulose Aerogel Fibers for Thermal Insulation and Multifunctional Applications

Cellulose aerogel fibers (CAFs) which have a porous nanonetwork and fiber geometry are promising candidates for thermal insulation or flexible devices due to their excellent thermophysical properties, renewability, and cost-effectiveness. However, their weak skeletal structure, low mechanical strength, combustibility, and poor moisture resistance remain significant barriers to their commercial viability. The establishment of physical and chemical cross-links is a potential strategy to enhance the strength, toughness, and overall performance of aerogels. In this work, interconnected networks of cellulose-based aerogel fibers are fabricated through continuous coagulation spinning and modified with the addition of 4,4′-methylene diphenyl diisocyanate (MDI) as the cross-linker. The CAFs modified with 1.5 wt % of MDI have good tensile strength (27.7 MPa), an ultrahigh Young's modulus (735 MPa), and excellent bending resistance even after they are knotted or looped for the tensile tests. The fabric made with MDI-modified CAFs is lightweight and flexible and has humidity insensitivity, with a better thermal conductivity of 0.09 in a 98% humidity environment compared with pristine CAFs. Significantly, the insulation of this fabric is almost the same as cotton wadding, yet only 1/5 of its thickness (RH = 50–60%). In addition, different functionalized aerogel fibers have been fabricated, such as those that are colored, antibacterial, and flame-retardant. The study shows the huge potential of cellulose-based aerogel fibers and textiles in producing the next generation of biomass-based high-performance thermal insulating devices.