Thermally Insulating Polybenzoxazine/Nanosilica Aerogel Ablation Resistant to 1100 °C for Re-Entry Capsules

Nanoporous phenolic resins have been widely used in the thermal protection system for the aerospace field owing to their ability to withstand high temperatures during ablation. Polybenzoxazine among other phenolic materials is considered as a potential candidate for thermal protection in re-entry capsules. However, polybenzoxazine aerogels often exhibit relatively increased thermal conductivity and limited high-temperature resistance, resulting in an adverse effect. Herein, we report a strategy of introducing a nanoporous silica-phase structure into a network of polybenzoxazine aerogels with an outstanding thermally insulated property and high-temperature (1100 °C) resistance. As-prepared aerogels possess a residual mass rate of up to 61.14% at 800 °C in oxygen. Even at 800 °C for 30 min, they can maintain the original shape, reflecting their dimensional ability, and the compressive stress of the aerogels under 2% strain is maintained at 1.323 MPa. After hydrophobic treatment, the water contact angle increased from 0° to 134°, which significantly improved the loss of thermal insulation performance caused by the absorption of water in the air. The study provides insight into the design of thermal protection material matrices with high quality residuals and excellent thermal insulation performance for re-entry capsules in the aerospace field.