Low Shrinkage and Robust Polyimide/Ultrafine Glass Fiber Aerogel for Efficient Heat Resistance and Oil/Water Separation

Polyimide (PI) aerogels have attracted a great deal of attention due to their low density and excellent heat resistance. However, PI aerogels produce large, irregular shrinkage during the thermal imidization process, resulting in decreased porosity and strength. In this work, the silane coupling agent-modified ultrafine glass fibers (mUGF) were mixed with polyamide acid solution, followed by freeze-drying and thermal imidization to prepare PI/mUGF aerogels. As the inorganic reinforced phase, mUGF with a high aspect ratio can significantly enhance the skeleton of the PI aerogel, reducing its volume shrinkage and avoiding the collapse of the porous structure during thermal imidization. The PI/mUGF aerogel exhibits low density (0.059 g/cm3), low volume shrinkage (18%), good mechanical properties, and excellent thermal stability and insulation (thermal conductivity as low as 31.4 mW/m·K at room temperature, 55.9 mW/m·K at 300 °C). Additionally, the aerogel also shows excellent adsorption properties (pump oil at room temperature: 24 g/g; at 200 °C: 17 g/g) and structural stability, which can be used to adsorb oils and organic solvents from polluted water. These findings can promote the design and development of low-shrinkage and robust PI aerogels for oil/water separation and thermal insulation.