Effect of DAPBO segment on the structure and performance enhancement of powder foamed BTDA-ODA polyimide

Achieving excellent thermal stability, good mechanical strength, and low-density in one product, is a big challenge in the design and synthesis of polyimide (PI) foams. We selected a rigid diamine monomer, 2-(4-aminophenyl)-5-aminobenzoxazole (DAPBO) to partially replace 4,4 '-oxydianiline (ODA) in BTDA-ODA system, and studied the effect on properties of foamed PI products. With various molar ratio between DABPO and ODA (0:5, 1:4, 2:3, 3:2, 4:1, 5:0), the diamine(s) polymerized with 3,3 ',4,4 '-benzophenonetetracarboxylic dianhydride (BTDA) and produced six PI precursors (PAE-0 similar to PAE-5). After foaming and thermal imidization, corresponding PI foams (PI-0 similar to PI-5) prepared. Among them, PI-3 has a glass transition temperature of 386 degrees C, which is 95 degrees C higher than PI-0, and its compressive strength reaches 1.32 MPa. Moreover, PI-3 has a uniform cell structure with an average pore size of similar to 200 mu m. The analysis results show that PI-3 is in a transition state from amorphous to partial crystalline, maintaining a balance between flexibility and rigidity. The addition of DABPO not only increases the rigidity of polymer molecular segments, but also introduces N and O atoms that can form intermolecular hydrogen bonds between molecules, which increases the packing density and arrangement regularity of polymer molecules.

Automated summary

The study successfully optimized the properties of foamed PI products by partially replacing the traditional ODA with a new rigid diamine monomer, DAPBO. PI-3 exhibited a higher glass transition temperature and compressive strength, as well as a uniform cell structure. The addition of DABPO not only increased the rigidity of polymer molecular segments, but also introduced N and O atoms that formed intermolecular hydrogen bonds, improving the packing density and arrangement regularity of polymer molecules.