Aerogels are lightweight, wispy materials whose volume is taken up almost entirely by air. These fluffy substances can be made from cellulose, silica, and other materials and used for thermal insulation, catalyst supports, and filters. But aerogels tend to be mechanically weak. So Xuetong Zhang and coworkers at the Chinese Academy of Sciences, Suzhou, devised a simple method for making aerogel fibers from a notoriously tough starting material—the aramid-based product known as Kevlar (ACS Nano 2019, DOI: 10.1021/acsnano.9b01094).
The team, which also included Zengwei Liu, Jing Lyu, and Dan Fang, first prepared a suspension of Kevlar nanofibers by stirring a few grams of the bulk material in dimethyl sulfoxide. Then, they created gel fibers by extruding the suspension via a pump-controlled syringe into a coagulation bath. Finally, they treated the product with alcohol and freeze-dried it, removing the solvent. As the material froze, it expanded to form a spongelike matrix, turning the Kevlar fibers into aerogels. The team then wove these into aerogel textiles. Compared with various organic and inorganic aerogels, the Kevlar aerogel exhibits similar surface area and thermal conductivity but has greater mechanical strength. It also shows good thermal and flame resistance and can be dyed and rendered hydrophobic.