Preparation and characterization of glass fiber/polyimide/SiO2 composite aerogels with high specific surface area

A glass fiber/polyimide (PI)/SiO2 composite aerogel (FPS aerogel) was prepared by dispersing glass fibers in PI/SiO2 hybrid sol derived from 4,4'-oxydianiline (ODA), pyromellitic dianhydride (PMDA) and tetraethoxysilane (TEOS) with supercritical CO2 fluid drying technology. The SiO2 primary particles were combined with PI chains which improved the strength of the composite aerogel, and the glass fibers inhibited the shrinkage deformation during the drying process by acting as the supporting skeletons. Effects of PI contents on the density, shrinkage, thermal conductivity and mechanical properties of the FPS aerogels were investigated. The as-prepared FPS aerogels had low densities (0.116-0.145 g/cm(3)), high specific surface area (844-963 m(2)/g), low thermal conductivity (0.0268-0.0280 W m(-1) K-1 at room temperature) and relatively high compression strength (0.12-0.29 MPa) with integrated nanostructures, fewer powders and stronger fiber/aerogel matrix interfaces. The density, the shrinkage, the thermal conductivity and the compression strength of the FPS aerogels increased with the increasing PI content. This research provided a new method employing PIs and glass fibers as strengthening phases to improve the mechanical properties of SiO2-based aerogels.