Layered double hydroxide/graphene oxide synergistically enhanced polyimide aerogels for thermal insulation and fire-retardancy

Environmentally friendly materials with lightweight, good thermal insulation and fire-resistance are highly required for energy efficient buildings. Here, layered double hydroxide (LDH) - graphene oxide (GO) synergistically enhanced polyimide (PI) aerogels with great thermal insulation, good thermal stability and excellent flame retardancy, have been designed and synthesized through a green environmental freeze-drying method followed by thermal imidization. LDH can be uniformly dispersed in aqueous solutions by electrostatic interactions with GO, thus resulting in uniform dispersion in PI matrix. Due to the physical interaction between the two kinds of nanosheets and PI, the pore size of PI/LDH-GO (PLG) composite aerogel was significantly reduced from 20 μm to 5 μm, leading to ultralow density (52 ± 3.6 mg cm−3), low thermal conductivity (36 ± 1.7 mW m−1 K−1), and high compressive modulus (26 ± 1.8 MPa). More importantly, the addition of two pollution-free fire-retardants (LDH-GO) endows the PLG aerogels excellent fire-resistant performance with the limiting oxygen index reach up to 43 ± 1.2%, reaching the nonflammable level. Therefore, this work paves a new way for anti-flaming and heat insulating materials with great potential for practical applications in energy efficient buildings.