Flexible and Flame Retardant Polyetherimide Silica Aerogel Thermal Insulation Membranes via Phase Separation

As the demand for energy-efficient thermal insulation continues to grow, the development of advanced materials plays a key role in minimizing heat loss, particularly at elevated temperatures around 400 °C. This study reports the fabrication of flexible and flame retardant polyetherimide silica aerogel thermal insulation membranes via a facile non-solvent induced phase separation(NIPS) process. By incorporating 50 wt% of nanoporous silica aerogel, the resulting membranes achieved an ultralow density of 0.20 g cm -3 and a thermal conductivity of 0.046 W m -1 K -1 , representing a 79.1% reduction compared to neat NIPS-derived polyetherimide (NPEI). The composites demonstrated superior fire safety, exhibiting a UL 94 V-0 rating, a limiting oxygen index of 31%, and a significant 73% reduction in peak heat release rate down to 62.4 W g -1 . Notably, the membranes maintained excellent structural integrity and dimensional stability without shrinkage even after exposure to 400 °C for 1 hour. Furthermore, the composites retained exceptional bending and torsional flexibility despite their high filler loading and porosity. The structural stability originates from a synergistic mechanism where the PEI matrix serves as a physical binder that transforms into a robust char to anchor the aerogel network, while the aerogel provides intrinsic thermal insulation. These NIPS derived membranes are promising candidates for next generation thermal management in aerospace and electric vehicle applications. • Flexible polyetherimide (PEI)–silica aerogel membranes were successfully fabricated through a scalable non-solvent induced phase separation (NIPS) process. • The PEI/Silica aerogel (SA50) membrane, fabricated via the NIPS process, exhibited a low density of 0.20 g cm -3 with high porosity. • NPEI/SA50 achieved excellent thermal insulation with a thermal conductivity of 0.046 W m -1 K -1 , driven by the synergistic effects between the porous PEI and silica aerogel. • The membrane showed outstanding flame retardancy, satisfying the UL 94 V-0 rating, limiting oxygen index (LOI) of 31%, and a 73% reduction in peak heat release rate (pHRR). • PEI acted as a binder to provide flexibility before carbonization and maintain the structural morphology after carbonization.