Improvement of Air Filtration Performance Using Nanofibrous Membranes with a Periodic Variation in Packing Density

This study reports a patterned nanofibrous membrane and its novel filtration performance. The nanofibers are prepared using an electrospinning technique, and the nanofibers are collected on a commercial nonwoven fabric covering a roller collector, which is prepared using a metal sheet with a round hole array. The nanofibers collected on the metal surface have a much denser structure than those in the hole areas. As a result, the patterned nanofibrous membrane has a different filtration performance (lower pressure drop and filtration efficiency) from the uniform nanofiber membrane, prepared under the same condition but using a smooth roller collector. When two layers of this patterned nanofibrous membrane are combined, the filtration performance depends on the layer arrangement. When the dual-layer membranes are arranged with the dense and loose packing areas staggering between the layers, the filter shows lower filtration resistance but higher efficiency than the uniform dual-layer filter. It is further shown that the staggered dual-layer membranes (made of polyacrylonitrile nanofibers) maintain high efficiency after eliminating the electrostatic charges. The efficiency meets air filter F9, the highest requirement according to the air filter standard (EN 779:2012), enabling a long service life.