Mechanically Robust Nanoporous Polyimide/Silica Aerogels for Thermal Superinsulation of Aircraft

Abstract

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.

Ultralow shrinkage polyimide hybrid aerogel composite enhanced with organic fibers for thermal protection

“…The actual temperatures of the hot stage were 51.6, 101. Compared with our previous work, the thermal insulation performance of PIAs-C decreased slightly at 150 C. 31 These results may be explained by the introduction of PUF increasing the pore size and density of PIAs-C. In general, the larger the pore size of aerogel, the higher the gaseous heat conductivity.…”

“…Finally, APTES was added to the PI sol and stirred for 15 min, followed by aging, solvent exchanges, and supercritical CO 2 drying. The detailed preparation process is described in our previous work, and the obtained PIAs have linear shrinkage of 14.29%, bulk density of 0.150 g cm À3 and thermal conductivity of 0.0239 W m À1 K À1 at 25 C. 31…”

“…While previous investigations achieved undeniable progress in decreasing the shrinkage rate of PI aerogels, the complexity of the preparation method is still the major obstacle to obtaining PI aerogels with excellent properties. 29,30 Based on our previous work, 31 the lightweight porous polyurethane fiber (PUF) was chosen as the reinforcement to further optimize the shrinkage of PI aerogel. The PI hybrid aerogel composite was prepared by combining PI/Si sol with PUF by simple impregnation.…”

Cure Kinetics and Thermal Decomposition Behavior of Novel Phenylacetylene-Capped Polyimide Resins

“…Polyimide (PI) resin is an organic material with extremely high heat resistance and can be widely used to manufacture composite structures that are resistant to temperatures as high as 300 °C [ 1 , 2 , 3 , 4 , 5 , 6 ], making it irreplaceable in the aerospace industry [ 7 , 8 ]. Among them, the heat resistance of phenylacetylene-capped polyimide resins can even reach 450 °C.…”

“…Polyimide (PI) resin is an organic material with extremely high heat resistance and can be widely used to manufacture composite structures that are resistant to temperatures as high as 300 • C [1][2][3][4][5][6], making it irreplaceable in the aerospace industry [7,8]. Among them, the heat resistance of phenylacetylene-capped polyimide resins can even reach 450 • C. They are capable of replacing aluminum alloy structures as resin-based materials in airplanes, missiles, and rockets, while reducing the weight by 15% to 30% [9].…”