Sheath-core structured Ca-alginate/PVA aerogel fibers via directed freezing wet-spinning

Biomass-based aerogel fibers have attracted increasing attention due to their renewable nature. However, their disadvantages, such as low mechanical strength, poor long-range order, and easy combustion, are still significant challenges. Herein, a directed freezing-assisted forced stretching strategy is developed to fabricate sheath-core structured Ca-alginate/polyvinyl alcohol (Ca-A/PVA) aerogel fibers with Long-range-ordered pores. The Ca-A/ PVA aerogel fibers (3:2 m/m) exhibit the best comprehensive mechanical properties in terms of low thermal conductivity of 0.0524 W center dot m- 1 center dot K- 1, a density of 0.1614 g center dot cm- 3, a porosity of 89.9 %, a tensile strength of 8.72 MPa, a tensile modulus of 249.7 MPa, a toughness of 1.98 MJ center dot m- 3, and a self-extinguishing time from the fire of <1.2 s. The Ca-A/PVA fabrics showed a maximum absolute temperature difference of 11.4 C at -20 degrees C and 14.0 degrees C at 60 degrees C compared to the plate temperature. The presented strategy is generalizable to other alginatebased aerogel fibers (e.g., alginate/guar gum).