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Lightweight microablation thermal protection materials are one of the crucial factors contributing to the rapid development of next-generation aircrafts. However, the maintenance of a high mass residual and long-term antioxidant capacity of the matrix after bearing high-temperature aerobic environments remains a major challenge. Herein, we put forward a strategy for constructing polybenzoxazine/silica hybrid aerogels depending on the introduction into silica inorganic phases by different technologic preparation routes, possessing excellent thermal insulation, superior self-extinguishing properties, and outstanding thermal stability. In detail, the mass residual rate of polybenzoxazine/silica aerogels (PSAs) as-prepared could reach up to 40.19%, mainly due to the reinforced networking structure by the introduction of silica that would be preserved well due to the inorganic phase nature in the high-temperature oxidizing environment. The pore size of polybenzoxazine/silica/chitosan aerogels (PSCAs) is mainly distributed within 5–35 nm, which contributes to obtaining a low thermal conductivity (0.037 W m–1 K–1) due to the pore size being smaller than the mean free path of stationary air at normal temperature and pressure. PSAs and PSCAs both exhibit excellent self-extinguishing properties, attributed to the presence of a large number of aromatic ring structures and the introduction of the silica inorganic phase in polybenzoxazine itself. The microscopic morphology, crystalline shape, and Si-related chemical bonding of PSAs did not significantly change after muffle thermal treatment, including the three-dimensional network structure composed of polybenzoxazine and silica. This study provides a kind of approach for designing a thermal protection material matrix with high mass residual and excellent thermal insulation performance in the aerospace field.

Polyimide aerogels (PIAs) are thermally insulating materials that possess various advantages, such as exceptionally high temperature resistance and low thermal conductivity, which make them great potential candidate materials to be applied in the area of thermal protection. However, under harsh mechanical stresses, the macro- and microscopic structural stability of PIAs may be compromised due to shrinkage/collapse, leading to performance degradation. Herein, we propose a homogeneous organic/inorganic hybrid formation strategy for constructing nanoporous polyimide/silica aerogels (PIAs-A) with exceptional mechanical strength and ultralow thermal conductivity. The results obtained indicate that PIAs-A have an optimal three-dimensional nanoporous network structure with a pore size distribution mainly within the range of 10–20 nm. Monitoring the temperature evolution of the material’s cold surface showed that it remained at a low temperature of 37.5 °C even when the material was placed against a hot surface of 150 °C. The residual mechanical strengths of the aerogels remained at a superior level (with strength degradation being less than 9%) after exposure to ultralow and high-temperature atmospheres. Furthermore, compressive stress values at 3% strain exceeded previously reported values for PIAs by 625 and 733% at −50 and 100 °C, respectively. Meanwhile, our aerogels displayed flame resistance even when exposed to a heat source of approximately 1200 °C, possessed favorable hydrophobic properties, and maintained dimensional stability up to 504 °C. The robust mechanical and thermal insulation properties of PIAs-A make them a promising substitute material for thermal superinsulation in aircraft.