Enhanced toughness and gas permeabilities of polyimide composites derived from polyimide matrix and flower‐like polyimide microparticles

Abstract The flower‐like polyimide (PI) based on 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride and benzidine was successfully obtained via solvothermal method. Using the flower‐like PI as organic fillers, the flower‐like PI/PI composites were fabricated by using 4,4′‐diaminodiphenyl ether and 1,2,4,5‐pyromellitic dianhydride as monomers through in situ polymerization and thermal imidization. The residual amino groups on the surface of flower‐like PI microparticles easily lead to the formation of chemical linkage between the flower‐like PI and PI matrix, which are benefit for tight interface and uniform dispersion. These experimental results showed that the broken elongation of the composites was significantly improved from 9.8% (pure PI) to 33.5% (PI‐4%), but the tensile strength and Young's modules were slightly sacrificed. The glass transition temperatures were mainly concentrated at around 352°C, while the 5% and 10% thermal decomposition temperature were slightly reduced. Furthermore, the light transmittance remarkably decreased from 75.9% (pure PI) to 4.3% (PI‐5%) at 550 nm. When the incorporation of flower‐like PI was 5%, an obvious increase of water uptake from 2.05% to 2.89% was noticed, and the water surface contact angle increased from 67.5° to 89.4°, indicating the increasing hydrophobicity. Additionally, with the increase of flower‐like PI fillers, the gas permeation flux of H 2 , CO 2 , O 2 , and N 2 enhanced by more than two times, and the selectivities of O 2 /N 2 and CO 2 /N 2 increased first and then decreased. Therefore, the flower‐like PI microparticles will be promising functional fillers to improve the properties of polyimide materials.