Flexible silica aerogel composites strengthened with aramid fibers and their thermal behavior

To meet the flexibility of some practical applications, aramid fiber reinforced silica aerogel composites (AF/aerogels) were successfully prepared, which possessed low density, remarkable flexibility and excellent thermal insulation properties. The microstructure of the AF/aerogels showed that the aramid fibers were inlaid in the aerogel matrix acting as the supporting skeleton, which established the foundation of mechanical properties. Three point bending indicated that improvement in flexibility could be achieved by ~ 5% fiber content without compromising the thermal insulation properties. As the fiber content increased, the density monotonously decreased to 0.142 g·cm− 3 while the thermal conductivity increased slightly with ranging between 0.0221–0.0235 W·m− 1·K− 1. The hot plate experiments indicated the transient thermal transfer was similar to one-dimensional heat transfer and the heat transfer characteristics were further analyzed in which a simple method to estimate the thermal conductivity was established according to the Fourier's law. TG-DSC analysis revealed that the thermal stability was up to approximately 285 °C which was mainly depended on the thermostability of pure silica aerogels. All these characteristics indicated that the as-prepared AF/aerogels were excellent thermal insulation materials and have great practical application prospects.