Melamine-Crosslinked Polyimide Aerogels from Supercritical Ethanol Drying with Improved In-Use Shape Stability Against Shrinking

Polyimide aerogels are promising for diverse applications owing to their nano-porous structure and superior properties. However, the shrinkage of melamine-crosslinked polyimide (MPI) aerogels has greatly compromised their performance in practical applications. In this study, supercritical drying with ethanol rather than CO2 is employed to enhance their in-use shape stability at high temperatures. The structure, thermal insulation, mechanical strength of the resultant aerogels as well as their shape stability are characterized. Experimental results reveal that the shape stability of MPI aerogels during use is greatly improved thanks to the in-advance baptism of supercritical ethanol drying. The aerogel shrinks by only 2.64 vol.% after being treated at 280 °C for 72 h. Besides, the MPI aerogel shows enhanced compressive strength and can easily support a load more than 20 000 times its own weight. The thermal conductivity of these aerogels varies from 0.034 to 0.046 W m−1 k−1, indicative of remarkable performance in thermal insulation. In addition, the aerogels that started to decompose at as high as 500 °C also perform well in thermal stability and char forming. It can be envisaged that the developed MPI aerogels with greatly improved in-use shape stability may have broad prospects for thermal insulation at high temperatures