Polyurea–Cellulose Composite Aerogel Fibers with Superior Strength, Hydrophobicity, and Thermal Insulation via a Secondary Molding Strategy

Aerogel materials, considered as the "miracle material that can change the world in the 21st century", owe their transformative potential to their high specific surface area, porosity, and low density. In comparison to commercially available aerogel felt, aerogel particles, and aerogel powder, aerogel fibers not only possess the inherent advantages of aerogel materials but also exhibit exceptional flexibility and design versatility. Therefore, aerogel fibers are expected to be processed into high-performance textiles and smart wearable fabrics to further expand the application field of aerogel materials. However, the aerogel fibers suffer from poor mechanical properties and intricate, time-consuming preparation processes. Herein, a simple and efficient method for crafting polyurea–cellulose composite aerogel fibers (CAFs) with superior mechanical properties is presented. The dried bacterial cellulose (BC) matrix was immersed in a polyurea sol, and the aerogel fibers were prepared via secondary molding, followed by CO2 supercritical drying. In a representative case, the CAFs obtained via secondary molding demonstrate outstanding hydrophobicity with a contact angle of 126°, along with remarkable flexibility. Significantly, the CAFs exhibit excellent mechanical properties, including a tensile strength of 6.4 MPa. Moreover, the CAFs demonstrate superior thermal insulation capabilities, withstanding temperatures ranging from 180 to −40 °C. In conclusion, with the successful fabrication of polyurea–cellulose CAFs, this study introduces a magic approach for producing aerogel fibers endowed with exceptional mechanical properties and thermal insulation. This advancement contributes to the development and application of aerogel materials in various fields.