Investigation of the properties and structure of semi-rigid closed-cellular polyimide foams with different diamine structures

Polyimide foam (PIF) has been extensively used as structural and thermal insulation materials. Five semi-rigid PIFs with different diamine structures were fabricated by unrestricted foaming process with polyester ammonium salt (PEAS) precursor powders. All PIFs exhibited a nearly homogeneous spherical closed pore structure with an average pore size of 123-335 mu m and a high closed-cell rate (87.4-95.5%). Results indicated that the molecular structure, melt viscosity and foaming temperature were important factors that affected the foaming process and pore structure. The values of 10% compression strength of PIFs at both 25 and 200 degrees C were in the range of 0.16-0.35 and 0.09-0.16 MPa, respectively, with PIFBTDA-MDA and PIFBTDA-DMBZ exhibiting the best mechanical performance. All PIFs exhibited outstanding thermal stability, with glass transition temperatures of 312-378 degrees C and 5% weight loss temperatures of 504.5-564.5 degrees C in nitrogen and 501.8-562.0 degrees C in air, respectively. The prepared PIFs exhibited extremely low thermal conductivity and thermal diffusivity, which can be used as thermal insulation materials. Based on above findings, the prepared semi-rigid PIFs demonstrate a great potential for being utilized as thermal insulation and structural support materials in high-tech fields such as aerospace, marine transportation, and microelectronics.

Automated summary

Polyimide foam has been utilized as structural and thermal insulation materials due to its nearly homogeneous spherical closed pore structure and outstanding thermal stability. The prepared foam shows extremely low thermal conductivity and thermal diffusivity, which makes it ideal for applications in high-tech fields such as aerospace, marine transportation, and microelectronics.