Density Modifications Toward High Mechanical Performance Nanocellulose Aerogels

Mechanical properties are crucial for the application of nanocellulose aerogels. In this work, a series of nanocellulose aerogels with solid content concentration gradient (0.5, 1.0, 1.5, 2.0 wt%) of precursor dispersion are prepared by freeze-drying method, and the effect of nanocellulose solid content on the mechanical properties of nanocellulose aerogels was investigated. As the solid content concentration increased, the internal microstructure of the aerogel underwent a transition from a sparse reticular structure to a tightly arranged lamellar structure. This transition led to a substantial improvement in the mechanical properties of the aerogel. At 50% strain, the compressive strength of the aerogel increased from 8.4 to 37.56 kPa with the increase of nanofibrillar cellulose solid content. Furthermore, the specific strength, specific modulus, and compressive modulus also increased, while maintaining a low density (20.02 mg/cm³) and high porosity (98.63%). This work confirms the feasibility of structural strengthening and mechanical property enhancement of nanocellulose aerogels by density modification, which provides a guidance for the design of durability enhancement of nanocellulose aerogels for broadening their application fields.