Preparation and thermal insulation performance study of anisotropic glass fiber/polyimide composite aerogels

In this study, glass fiber/polyimide composite aerogel (GF/CLPI) was successfully fabricated via directional freezing technology. By precisely controlling the mass ratio of polyamic acid salt to glass fiber (GF) powder (ranging from 5:1 to 1:2), and through high-speed blending, liquid nitrogen-induced directional crystallization, freeze-drying, and stepwise thermal imidization processes, anisotropic structured materials were obtained. Microscopic characterization revealed that the axial cross-section exhibited a honeycomb-like interconnected pore structure. At the same time, the radial direction formed a layered orientation. GF were uniformly embedded in the polyimide pore walls, resulting in a homogeneously distributed reinforcing phase. Performance tests demonstrated that the material had an initial decomposition temperature of 490 °C in air and 550 °C in nitrogen. Furthermore, the radial thermal insulation performance (thermal conductivity ranging from 27.4 to 36.6 mW·m −1 ·K −1 ) was significantly superior to that in the axial direction (thermal conductivity ranging from 27.5 to mW·m −1 ·K −1 ). At elevated temperatures, the polyimide matrix and GF cooperatively formed an insulating carbonized layer, thereby endowing the material with self-extinguishing properties. This structure-property coordinated regulation strategy offers a novel approach for the development of advanced lightweight thermal insulation materials.