Enhanced hydrophobicity, mechanical and sound absorption properties of polyimide aerogels reinforced by polyacrylonitrile nanofibers

Despite its lightweight and porous nature, aerogel has been extensively investigated. However, there remains an urgent need to further enhance its mechanical strength . Many reports detail strengthening aerogel matrix with various fibers as supporting skeleton. Here, composite aerogels were prepared with polyimide serving as the matrix and polyacrylonitrile nanofibers as the filler. A more in-depth exploration was carried out into the transformation of the aerogel structure in relation to the nanofiber content. Additionally, an analysis was conducted on the impact of the structure on mechanical properties, heat insulation , sound absorption , and water absorption. It was found that the nanofibers effectively optimize the compressive properties of the composite aerogels, while also satisfying the requirement of resilience. The maximum compressive stress and corresponding elastic modulus of the aerogels were 1.83 MPa and 22.03 MPa, respectively. After soaking for 24 h, the lowest water absorption was only 5.56 %, and the sound absorption coefficient remained almost unchanged under such conditions. The thermal conductivity of all aerogels was stable at 0.0413–0.0428 W/m·K. In summary, this work provides a preparation method and design concept of aerogel that can meet the requirements of high strength and low water absorption based on the sound absorption and heat insulation , The rationally designed aerogel shows significant potential for harsh high-temperature and high-humidity applications. • PPAs composite aerogels exhibit large specific surface area and favorable mechanical property compared with the pure PI aerogel. • The water absorption of PPAS is only 5.6 % after soaking 24 h. • PPAs exhibit high average sound absorption coefficient.