Effect of alumina on the structure and properties of polyimide matrix films

To improve the properties of polyimide (PI), different mass fractions of alumina (Al2O3) nanoparticles, unmodified or modified by KH550, were incorporated into PI matrix to form PI/Al2O3 hybrid films by in situ polymerisation. The effects of Al2O3 additives on the structure, dielectric and mechanical properties of the films were studied. Fourier transform infrared spectroscopy confirmed the successful preparation of PI/Al2O3 hybrid films, and the microstructures of the samples showed a more uniform dispersion of the modified Al2O3 nanoparticles than the unmodified ones in the matrix. The dielectric constant of the films increased with increasing filler content, and the maximum electrical breakdown strength of 311 MV m−1 was obtained with a filler content of 8.0 wt-% modified Al2O3 in the matrix. Both unmodified and modified Al2O3-reinforced PI hybrids demonstrated improved mechanical properties compared with the PI matrix. Moreover, the properties of films with Al2O3 modified by KH550 were better.