The report gives results of an extension of studies of the influences of fiber geometric properties on the ability of nonwoven fabrics to filter particles from gas streams to a wider range of geometric variables and to the measurement of capture efficiencies for particle sizes in the respirable range down to 0.024 micrometers. In addition to the light-weight (about 0.17 kg/sq m) fabrics studied earlier, commercial-weight (about 0.5 kg/sq m) fabrics were prepared from experimental fibers and evaluated in flat patch form. Some of these heavier fabrics were made into filter bags and tested in a laboratory baghouse equipped with automatic pulse-jet cleaning. Fibers with certain cross-sections (especially, trilobal) were found to increase flyash particle capture efficiency, especially in the submicron sizes, once a cake forms. The improvement occurs with no pressure drop increase. In comparing rough and smooth fibers, certain rough fibers appear to improve capture of the smallest particles after dust cake formation. Crimped fibers lead to better flyash filtration performance than uncrimped, but the crimp frequency has no noticeable effect. The capture efficiency increase accompanying a fiber diameter decrease follows different empirical relationships, depending on cake formation.

Prepared under grant no. R800042, program element no. EHE624. "EPA 600-7-77-115." "October 1977." Includes bibliographical references.