Role of capillarity in penetration into and flow through fibrous barrier materials

Hydrophobic fibrous media, in the form of barriers, provide protection to its user against fluids. Important aspects to consider are the pressure at which liquids (nonwetting fluids) will penetrate into the fabric and the rate at which it will flow through. At the same time we need to consider the comfort level that the fabric provides, that is, the pores should be large enough to allow the exchange of air. The objective of this study was to develop an experimental technique to determine (1) the displacement pressure of medical barrier fabrics in combination with aqueous solutions and (2) the flow rates once the aqueous solutions had penetrated. A pressure/flow cell was used to make these determinations during sequences of increasing and decreasing pressures applied to the nonwetting fluids (aqueous solution). The resulting flow rate–pressure curves exhibited hysteresis, that is, lower flow rates existed during increasing pressures (increasing liquid contact) than during decreasing pressures (decreasing liquid contact) at corresponding pressure values. The reasons for this hysteresis were investigated. The flow rate–pressure curves also provided information about the pore size distributions of the fabrics. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 841–846, 2005