Designing Nonwovens to Meet Pore Size Specifications

New nonwovens applications in areas such as filtration require a media designed to particular pore size specifications in the 3 to 20 micron range. The purpose of this work was to develop a basis by which to design and construct a fabric with given pore size specifications. While doing so we have provided a validation for two different mathematical models. We have also found that bicomponent spunbonded islands-in-the-sea nonwoven fabrics can be designed very precisely to achieve target pore diameters and porosity. Mathematical models can be used to develop fabric specifications in the standard manufacturing terms of basis weight and fiber diameter. Measured mean flow pore diameters for the test fabrics showed excellent correlation to targeted mean flow pore diameters for both models. The experimental fit to the Bryner model is the better of the two, but requires specification of fabric thickness in addition to basis weight and fiber diameter to achieve actual mean pore diameters that closely match target values. Experimental validation of the influence of fabric thickness on the mean flow pore diameter at constant basis weight and fiber diameter remains open for further investigation. In addition, achieving complete separation of the island and sea polymers along with unbundling of the island fibers remain areas for improvement.