Thermally bonded nonwoven filters composed of bi-component polypropylene/polyester fiber. II. Relationships between fabric area density, air permeability, and pore size distribution

The relationships between the pore size, fabric area density, and air permeability of the three-dimensional (3D) nonwoven filter samples produced using a new 3D forming process has been studied. Results indicate that the thermally bonded nonwoven filter samples consist of multiple filtration layers of interconnected pores and tortuous pore paths through the fabric thickness. Both the bubble point pore diameter and the mean flow pore diameter of the produced filter samples increase linearly with increase in the reciprocal of the fabric area density. The air permeability of the nonwoven filter samples decreases significantly to a certain value with increasing fabric area density, and then becomes almost stable with further increasing of fabric area density. The measured pore size data in the thermally bonded nonwoven samples were found to follow all the bi-normal, bi-lognormal, and bi-Weibull distributions. Taken into account together the pore structure, pore size distribution, air permeability, and fabric area density, the new 3D forming system can substitute most of the commercial polyester filter media with significantly reduced costs. © 2006 Wiley Periodicals, Inc.