Preparation of Thermosetting/Thermoplastic Polyimide Foam with Pleated Cellular Structure via In Situ Simultaneous Orthogonal Polymerization

Miscible thermosetting/thermoplastic aromatic polyimide foam is prepared by in situ simultaneous orthogonal polymerizations, where the linear polyimide (PI) is formed by condensation polymerization from polyester ammonium salt (PEAS) and the cross-linked bismaleimide (BMI) is synthesized through addition polymerization from 4,4'-bismaleimide diphenylmethane (BDM). A unique pleated cellular structure is formed after the polyblend foam is cured at high temperature; here, 2D FT-IR correlation analysis is employed to detect the detailed chemical reactions during the thermal foaming progress. The simultaneous orthogonal polymerization is confirmed, and the cross-linking reaction of BDM is found to be divided into two stages. The pleated structure formed in the second stage significantly improves the thermal insulation property of the polyblend foam-the effective thermal conductivity decreases from 427.5 to 77.S mW.m(-1).K-1 at 300 degrees C with 15 wt % BMI. Meanwhile, the polyblend is miscible and foams only have one single glass transition temperature (Tg), which BMI. This polyblend polyimide foam will be a promising porous material for thermal insulation applications in extreme environments, and the method to prepare the pleated cellular structure in this work should provide a strategy to develop advanced polymeric foam materials.