Flexible and interlocked quartz fibre reinforced dual polyimide network for high-temperature thermal protection

The booming aerospace industry presents significant challenges for lightweight and flexible thermal protective materials for spacecraft and related apparatus. Despite polyimide aerogels being potential candidates with outstanding thermostability, their low strength and instability at ultra-high temperatures limit their practical applications. We report a lightweight composite interlocked by a dual polyimide network and a 3D quartz fiber felt, with attractive flexibility, excellent thermostability, long-term thermal insulation under both static and dynamic conditions, as well as superior flame retardancy and hydrophobicity. The robustness of the composite was endowed by the embedment of linear polyimide, which strengthened the felt and chemically bonded with the network polyimide. The resulting composite with a density of 0.147 g cm⁻³ exhibited low thermal conductivity (0.036 W m⁻¹ K⁻¹), reversible bending and compressive behaviors (strains of 15% and 60%, respectively), high pyrolysis temperature in air (445 °C), sustainable thermal insulation at 300-400 °C, and even 30 min-insulation at 1200 °C with a space-saving thickness (8 mm). These integrated performances made the composite promising for wide-temperature thermal protection where both efficient thermal insulation and flexibility are demanded.