Preparation of tetraethoxysilane-based silica aerogels with polyimide cross-linking from 3, 3', 4, 4'-biphenyltetracarboxylic dianhydride and 4, 4'-oxydianiline

Polyimide cross-linked silica aerogels with different weight percentages of polyimide were prepared through sol-gel technology and supercritical CO2 fluid drying technology. Tetraethoxysilane (TEOS) was used as a silica source precursor, 3-aminopropyltriethoxysilane (APTES) end-capped polyimide was used as a cross-linking agent, derived from 3, 3', 4, 4'-biphenyltetracarboxylic dianhydride (BPDA) and 4, 4'-oxydianiline (ODA). The acid produced during the imidization process catalyzed the hydrolysis reaction without additional catalyst. After condensation reaction catalyzed by ammonium hydroxide solution, the polyimide cross-linked silica gels were obtained and then dried in supercritical CO2. The polyimide cross-linked silica aerogels have low density (0.132 similar to 0.187 g/cm(3)), high specific surface area (623-741 m(2)/g), low thermal conductivity (0.0306 similar to 0.0347 W/m K at room temperature), relatively high compressive strength (1.03 similar to 3.82 MPa) and high thermal decomposition temperature (360 A degrees C). This research provided a simple and efficient method that used the polyimide as a strengthening phase to improve the mechanical properties of TEOS-based silica aerogels. [GRAPHICS] .