Reduced shrinkage and mechanically strong dual-network polyimide aerogel films for effective filtration of particle matter

Abstract

• Innovative use of ultra-light nanofiber membrane as a template for preparing lightweight polyimide aerogel, which can effectively adjust the pore structure. • The prepared aerogel membrane show greatly improved mechanical properties (approximately 11 MPa) and good dimensional stability, which is much better than that of pure PI aerogel films. • The prepared aerogel membrane exhibits high filtration efficiency (99.91% for PM2.5) for air particulate at a small basis weight and may be application under higher temperatures and hazardous environments. Polyimide (PI) aerogel materials have been proven to have wide application potential in the fields of electronics, heat insulation, filtration, sensors, etc. due to high specific surface area and unique nanoporous structure. However, dimensional instability and poor tensile properties has been regarded as issues that limits its application, especially aerogel membranes, under severe temperatures. In this work, the electrospun polyimide nanofiber (PINF) membrane has been used as a self-reinforced template to successfully prepare PI composite aerogel membranes with greatly improved mechanical properties. The tensile strength can reach about 9–11 MPa, which is significantly higher than the corresponding pure PI aerogel film. At the same time, the composite aerogels also show good dimensional stability even after high temperature treatment. More importantly, observed by scanning electron microscope (SEM), PI composite aerogel films with hierarchical porous structure can be effectively constructed by adjusting the solid content of PI sol, especially at a low solid content of 1 wt%. In addition, the unique nanoporous structure between nanofibers makes it possible to maintain high filtration efficiency (99.91% for PM2.5) at a small basis weight.