Abstract: Polyimide （PI）/glass powder composite films were prepared through a two-step thermal imidization polymerization process using pyromellitic dianhydride （PMDA） and 5-amino-2-（4-aminophenyl） benzoxazole （BOA） as monomers and glass powders as a filler， and their structure and thermal and mechanical properties were investigated. The as-prepared composite films were fully imidized by showing a yellowish brown color. The composite films exhibited excellent thermal properties with a 5 wt% weight loss temperature between 556 and 565 °C， and their residual char yields were more than 60 wt%. Moreover， the composite films present a glass transition temperature of above 410 °C and a low thermal expansion coefficient of less than 5.3 ppm/K. Their tensile strength was determined to be 164~242 MPa， their tensile modulus ranged from 4.7 to 7.5 GPa， and their elongation at break was higher than 6.0 %. This indicates excellent mechanical performance of the composite films.

Key words: polyimide, glass powder, film, thermal behavior, mechanical property