Characterization by Mercury Porosimetry of Nonwoven Fiber Media with Deformation

The porosity and pore diameter distribution are important characteristics of nonwoven fiber media. With the advent of electrospinning, the production of mats of nonwoven fibrous materials with fiber diameters in the 0.1-10 μm range has become more prevalent. The large compliance of these mats makes them susceptible to mechanical deformation under the pressures attained in a typical mercury porosimetry experiment. We report a theoretical analysis of the liquid volume measured during liquid intrusion porosimetry in the presence of deformation of such mats by one of two modes: buckling of the pores or elastic compression of the mat. For electrospun mats of poly(ε-caprolactone) with average fiber diameters ranging from 2.49 to 18.0 μm, we find that buckling is the more relevant mode of deformation, and that it can alter significantly the determination of pore diameter distributions measured by mercury porosimetry.