Macroporous Polyimide Aerogels: A Comparison between Powder Microparticles Synthesized via Wet Gel Grinding and Emulsion Processes

Abstract

It is noteworthy to mention that synthesizing the polyimide aerogel powder, which is carried out in this study, benefits from two advantages: (i) the powder particles can be used for some specific applications where the monolith is not suitable and (ii) there is a possibility to investigate how a polyimide aerogel monolith can be made through the polyimide powder to reduce its cost and cycle time. In this study, two straightforward methods, wet gel grinding and emulsion, are introduced to prepare polyimide aerogel powders using ambient pressure drying. The microscopic properties of interest, including skeletal and porous structures, microparticle size and assembly, combined with macroscopic properties such as thermal stabilities and conductivities (0.039 W/m·K), confirm that the fabricated microparticles with a size in the range of 7–20 μm and porosity in the range of 65–85% are thermally stable up to 500 °C.

Fabrication and Characterization of a High-Strength Polyimide/Thermoplastic Polyurethane Composite Aerogel with Hydrophobicity and Low Thermal Conductivity

“…Aerogel with high porosity and low density emerges as an ideal thermal insulation material, owing to readily and efficiently restraining heat transmission, convection, and radiation in a solid phase. − Polyimide (PI) aerogel is a high-performance polymer possessing an imide ring in its main chain, rigid skeleton structure, and high conjugation effect of the aromatic heterocyclic ring, endowing it excellent mechanical strength . Owing to high-temperature resistance and effective heat insulation, PI has been used in aerospace, heat insulation and flame retardancy, adsorption and cleaning, photoelectrochemistry, etc. − Recently, PI-based aerogel composites have drawn attention, because the PI content overcomes the brittleness of inorganic aerogel, but their poor hydrophobicity causes difficulties from application perspectives …”