Fabric Reinforced Polybenzoxazine Aerogel Composite With Lightweight, High Compressive Strength, and High‐Temperature Resistance to 1100°C

ABSTRACT High‐temperature resistance polymer composites are crucial for application in aerospace field. Polybenzoxazine (PBz) aerogel is a novel insulation material with excellent mechanical properties, low bulk density, and low thermal conductivity, which has potential application in thermal protection systems. However, the improvement of high residual char rates for shape‐keeping purposes at high‐temperature is still a critical challenge. Herein, a novel kind of PBz aerogel composite reinforced with mullite‐fiber fabric (PBZ‐MF) is prepared by sol‐immersion‐gel strategy. The prepared composite integrates the nanoporous structure of aerogel with the fascinating properties of mullite‐fiber fabric, resulting in relatively low thermal conductivity (0.0557–0.0647 W m −1 K −1 at 25°C and normal pressure), lightweight (0.41–0.47 g cm −3 ), outstanding flame resistance (self‐extinguishing time as short as 0.7 s), and high compressive modulus (20.611–32.656 MPa). Furthermore, PBz‐MF demonstrates exceptional high‐temperature resistance and shape‐keeping properties even at 1100°C. This work provides valuable insights into the development of lightweight insulation materials and expands the potential applications of aerogel composites in thermal protection systems within the aerospace field.