Synthesis of waterborne polyurethane aerogels-like materials via freeze-drying: an innovative approach

Waterborne polyurethane (WBPUR) aerogels using acetone method and freeze-drying procedure have been successfully synthesized. The morphology, chemical structure, and thermal and mechanical properties of obtained aerogels were analysed by means of scanning electron microscopy, Fourier-transform infrared spectroscopy, contact angle, thermogravimetric analysis, differential scanning calorimetry and dynamic mechanical analysis. In addition, the influence of the solids content in the hydrogel (2–15 wt.%), obtained by varying the amount of water added in the suspension, on the density and thermal conductivity was evaluated. Obtained results demonstrated that the properties of aerogels strongly depend on the solids content assayed in the parent solution. As the solids content in the WBPUR aerogels increases, the density and thermal conductivity for materials with 2.5 and 10% solids content follow an upward trend, while their elasticity decreases. Materials with solids content below 2.5% and above 10% have not demonstrated adequate processability due to their high deformity and hardness, respectively. The drying methodology (freeze-drying) can be profitably used to prepare aerogels-like materials in a cost-effective way. Graphical abstract Illustration of the alternative preparation process of WBPUR aerogels and its potential industrial application.