Facile Adjusting for Cells of Lightweight Isocyanate-based Polyimide Foam and Operable Combination between Different Distinctive Acoustic Foams for Higher Performance

New ambient sound absorption material,lightweight isocyanate-based polyimide foam(IBPIF),was fabricated by operable combination between different distinctive acoustic IBPIF.Cellular structure of IBPIF was facilely and obviously adjusted by increased slurry temperature corresponding to change in distinctive acoustic properties.Moreover,density of all IBPIF kept at only 12-17 kg/m3.With increasing slurry temperature from 0℃to 40℃,cell size and window opening rate gradually increased from 553μm to 791μm and from 6.85%to 58.46%,respectively.In this study,IBPIF generated by slurries at 0℃(marked as PIF-2)and 40℃(marked as PIF-6)showed best and distinctive acoustic behavior in 315-800 Hz and 800-6300 Hz regions,respectively.After acoustic behavior study of combined IBPIF prepared by stitching combination between two distinctive acoustic IBPIFs,results showed that only when PIF-6 sheet used as sound receiving surface even though with thickness of only 10 mm could the combined IBPIF possess the best acoustic level in 800-6300 Hz region as PIF-6.Furtherly,acoustic behavior in 315-800 Hz region could be significantly enhanced by increasing thickness of PIF-2 and could reach or close to the best acoustic level.