Super-flexible and low-shrinkage polyimide aerogel composites with excellent thermal insulation: Boosted by SiO2 micron aerogel powder

•A novel approach to increase the flexibility of PI aerogel composites is proposed.•Double crosslinking enhancement of SiO2 micron aerogel powder and 1,3,5-benzotrimonium chloride (BTC).•Ingenious design of the microstructure of the PI aerogel composites. Polyimide (PI) aerogel composites were synthesized using 4,4′-diaminodiphenyl ether (ODA) and 1,3-bis(4-aminophenoxy)neopentane (BAPN) as diamine monomers, and biphenyl-3,3′,4,4′-tetracarboxylic dianhydride (BPDA) as dianhydride monomers. This study examined the impact of varying proportions of SiO2 micron aerogel powder and the addition of BTC on the properties of the composites. The prepared composites showed ultra-high flexibility (180° folded) with the thickness of 3–4 mm, high thermal stability (95 % weight retention at 501 °C) and thermal insulation performance with ultralow thermal conductivity of 0.033 W/(K·m).