Abstract The quality factor ( QF ) of an air filter depends on the pressure drop and filtration efficiency. In this study, mixing thick polycarbonate (PC) fibers into a polypropylene (PP) melt-blown (MB) nonwoven improved the QF . We investigated how the PC fiber diameter affected QF . A series of MB nonwoven samples were prepared by changing the PC throughput rate ( L ) from 0 to 90 cm 3 /min, while maintaining a constant PP throughput rate. We used X-ray computed tomography to evaluate the nonwoven characteristics, i.e., the thickness, fiber diameter, fiber orientation, and fiber volume fraction. We used these characteristics to determine the relationship between the nonwoven structure and QF . The PC fiber diameter increased with L , and the initial nonwoven thickness increased linearly with the PC fiber diameter. However, loading at 0.5 and 50 kPa considerably decreased the nonwoven thickness for all L values except the maximum L . The enhanced QF for samples prepared using L values of 15–52.5 cm 3 /min resulted from a decrease in the pressure drop caused by the incorporation of thick fibers, as has been previously reported. The further enhancement of QF for the sample produced using the maximum L of 90 cm 3 /min was attributed to the uniform fiber volume fraction and fiber orientation in the thickness direction of this sample (the fiber orientation factor increased slightly in the thickness direction).
Shibata et al. (Wed,) studied this question.