Fig. 9: Filtration membrane for vehicle exhaust.

a PI nanofiber for vehicle exhaust filtration. The nanofiber membrane has various values of optical transmittance of 45%, 58%, 64%, 71%, 89%, and 95%, denoted as PI-45, PI-58, PI-64, PI-71, PI-89, and PI-95, respectively. b The PM_2.5 filtering efficiency of PI nanofibers. PI nanofibers with optical transmittance of 45% have the highest efficiency of 99.98% at 350 °C. However, at 370 °C, the efficiency decreases significantly. (reproduced with permission from ref.¹⁰ copyright (American Chemical Society, 2016)). c The fabrication process of wrinkled PI nanofibers, including the SEM and TEM images of fabricated nanofibers. Wrinkled PI nanofibers are obtained by adding 20 wt% of PAN to PI (denoted as PI-20). d The efficiency of PM filtering with various particle sizes at room temperature of fabricated nanofibers (PI-0, PI-5, PI-10, and PI-20 nanofibers). The PI-20 has the highest efficiency for all PM sizes, with even a PM_0.3 efficiency of 99.99%. e TGA curves of fabricated nanofibers. The mass of the pure PI nanofibers starts to decrease significantly at 505 °C. (reproduced with permission from,²⁵¹ copyright (American Chemical Society, 2020)).