Influences of Fiber Geometry on the Performance of Nonwoven Air Filters

Abstract

The principal aim of this study was the evaluation of the influence of five fiber properties on the filtration performance of model nonwoven fabrics made from the fibers. Variables studied were cross-sectional shape, linear density, surface roughness, crimp, and staple length. Two levels of each were represented in a set of 32 polyester fiber samples. Non woven fabrics made from each of these were used to filter fly-ash particles from a stream of air using a test apparatus designed for the purpose. The relative filtration performances associated with a change in each fiber property were assessed from measurements of pressure drop across the filter, collection efficiency, and particle-size distribution. Sta tistical analysis showed that: 1) efficiency is improved by the use of trilobal rather than round cross-section fibers with no detrimental effect on drag; 2) efficiency and drag are both improved by the use of crimped rather than uncrimped fibers; and 3) efficiency is improved by the use of 3-denier rather than 6-denier fibers but at the cost of greater drag. Curves relating efficiency to particle size seem to indicate that rougher fibers are more efficient in removing finer particles. In general, emdency improvements imparted by changes in fiber geometry are especially pronounced for fine-particle filtra tion (∼2.5 microns).