Fabrication of rigid polyimide foams by adopting active crosslinking strategy

Rigid polyimide foams (PIFs) with excellent mechanical and thermal properties were fabricated by thermal foaming of active cross-linkable units terminated polyester ammonium salts (PEAS) precursor powders. The active cross-linking strategy was realized by breaking C C bonds in maleic anhydride under heating treatment. Results showed that the formation of cross-linked structure before complete imidization effectively resisted matrix shrinkage and endowed PIFs with outstanding mechanical properties . The room temperature compressive strength and modulus of PIFs with four repeating units reached as high as 2.34 and 56.1 MPa, respectively. Moreover, the PIFs exhibited excellent thermal properties with onset decomposition temperatures ranging from 490 to 550 °C and the glass transition temperatures exceeding 290 °C. The PIFs displayed better thermal insulation , and the values of thermal conductivity fell within a range of 0.056–0.090 W m −1  K −1 , which demonstrates potential application as high temperature resistant structural materials in aerospace and energy sectors.