(496b) Permeability of Electrospun Mats Under Pressure Driven Flow

Abstract

Electrospun mats are promising in filtration applications because of their high surface-to-volume ratio (10-500 m²/g for 10-500 nm fiber diameter) and high porosity (>0.9), which results in high permeability constants [1,2]. However, electrospun mats are also highly compressible, hence their porosity decreases with increasing pressure. This compressibility of the mat can reduce the benefits of high porosity in filtration applications. An understanding of the extent of the reduction in permeance upon compression for electrospun mats is vital for performance comparison with other commercial filtration membranes in filtration processes.

Hydraulic permeability of electrospun mats under flow-induced compression has been modeled and verified experimentally. The permeation model accurately estimates the changes in solidity, and hence the permeability of the electrospun mats, over a range of pressure differentials. The model is based on Darcy’s law using Happel’s permeability equation coupled with a compression model of the form, P_m=kE(ϕⁿ-ϕ₀ⁿ) where P_m is the compressive stress and ϕ is solidity, in accord with the analysis of Toll [3]. Hydraulic permeability of electrospun mats of bis-phenol A polysulfone (PSU) comprising fibers of different mean diameter, annealed at temperatures at and above the glass transition of the polymer, was measured for feed pressures ranging from 5 kPa to 140 kPa. By using kE value as a fitting parameter in the permeation model, permeation test may be used as an alternative tool to estimate the kE value, which is difficult to measure accurately from compression testing. The electrospun mats experience a decrease of more than 60% in permeability constant, compared to a 32% decrease for a commercial membrane, because electrospun mats are more compressible than the commercial membrane. 

References

[1]       Yoon K., Hsiao B., Chu B. (2008) J. Mater. Chem. 18, 5326-5334.

[2]       Burger C., Hsiao B., Chu B. (2006) Annu Rev Mater Res 36 (1), 333-368.

[3]       Toll S. (2004) Polymer Engineering & Science 38 (8), 1337-1350.