Fabrication of a polycarbonate/polypropylene fiber mix air filter using a melt-blowing apparatus with different nozzle diameters

Air filter filtration efficiency is determined by the particle capture-to-pressure drop ratio. We produced a melt-blown nonwoven fabric with a specific fiber diameter distribution by blending thick fibers using nozzles with different diameters. When a polycarbonate was extruded from large holes, the particle transmittance rate doubled and the pressure drop decreased by 1/3. Consequently, the quality factor increased by 1.5-fold. Most of the fibers in a pure polypropylene sample had diameters below 20 µm, even when the polypropylene was extruded from large holes. However, when polycarbonate was extruded, the distribution widened to 40 µm, and the proportion of fibers in the 20‒40 µm range increased. The pore size distribution followed a similar tendency of fiber distribution. Analysis of the fibers with diameters above 20 µm revealed that the fiber volume fraction widened markedly in the thickness direction. That is, a greater number of thick fibers ensures more air passages, thereby decreasing the pressure drop. The thick fibers form large pores, which increases the length of the flow paths of the aerosols. This increases the probability of particles contacting the fibers and suppresses particle penetration. The changes described above explain the increase in the quality factor.