Robust cellulose composite aerogels with enhanced thermal insulation and mechanical properties from cotton waste

Bio-based aerogels are sustainable and eco-friendly materials that have gained increasing attention. However, their development is hindered by complex technological processes and unsatisfactory mechanical properties. To obtain a multi-scale hierarchical micro-meso porous composite aerogel with extraordinary thermal insulation and mechanical properties via simple and facile preparation process, we used oxidized cotton linter fiber (CF) as the skeleton and reinforcement, oxidized microcrystalline cellulose (MCC) as the supporting and filling matrix, and PVA as the crosslinking agent and a good glue to enhance the interaction between CF and MCC, and the porous network of the composite aerogel. The composite aerogel is very light, strong, and flexible. The best obtained composite aerogel has a apparent density of only 67.5% of the pure cotton fiber composite aerogel (CF0), a maximum compressive stress of 1.22 MPa, which is 22 times higher than the pure microcrystalline composite aerogel (MCC0), and a thermal conductivity of 0.0335 W/m.K, which is 89% lower than CF0. These properties make the composite aerogel suitable for various thermal insulation applications, such as protective clothing for extremely cold environment.