Tunable Thermal Conductivity and Mechanical Properties of Polyurethane Aerogels Showing High Transparency

Herein, the synthesis of polyurethane-based aerogels is described. Then, these materials are characterized and the influence of different catalyst contents in the formulations on the final properties is studied. Tunable thermal conductivities are reached by changing the catalyst amount, since this factor also has a strong effect on the aerogel nanostructures. Thus, thermal conductivity values ranging from 11.7 to 24.2 mW/mK can be obtained, reaching the most insulating value for polyurethane aerogels in the literature. Finally, the stiffness and elasticity of these materials was evaluated by mechanical compression experiments. The elastic modulus followed a clear trend with the catalyst concentration, and, therefore, with the porous structure obtaining values from 0.13 to 6.32 MPa. Thus, in this work, the structure-properties relationship of these materials has been explored, achieving the production of super-insulating materials with tailorable stiffness in combination with optical transparency leading to on-demand applications. The exceptional insulation of silica aerogels was reached at the same time that their general brittleness was improved while keeping good transparency to visible light (85 %, 650 nm) becoming promising materials.