Dual-channel coextrusion printing strategy towards mechanically enhanced, flame retardant, and thermally stable polyimide-silica aerogels for thermal insulation

Extrusion-based 3D printing enables the on-demand shaping of aerogels with compatible material compositions and tailored geometric features for functional applications. Herein, a novel dual-channel coextrusion printing strategy has been proposed for fabricating polyimide-silica aerogels. The implementation of printing processes depends on the fluid intermixing of inks and catalyst liquids in the specific zig-zag structure, as well as the coextrusion of their mixtures through a single nozzle. After coextrusion printing, chemical imidization solidification ensures that 3D-printed aerogels achieve high shape fidelity in macroscopic geometries. Benefiting from the microscopic composite phases of polyimide and silica, 3D-printed aerogels exhibit improved mechanical properties (specific modulus, 54.45 kN·m·kg−1), outstanding flame retardancy (LOI value, 55.3 %), and excellent thermal stability (linear shrinkage, <5 % at 400 °C). More importantly, nanoscopic pore characteristics, such as low density (0.196 g·cm−3), high surface area (518 m2·g−1), and concentrated pore diameter distribution (∼30 nm), endow 3D-printed aerogels with a low thermal conductivity of 20.80 mW·m−1·K−1, which presents great potential for thermal insulation applications in medium-high temperature environments. This work would offer feasible guidelines for the design and fabrication of shape-dominated functional materials by additive manufacturing.