Contact Angles of Porous Media by Liquid Extrusion and Comparison to Measurements from a Novel Inclined-Plate Technique

Abstract

Most techniques for characterization of the pore structure of porous media, such as mercury porosimetry, liquid extrusion porosimetry, and permporometry, among others, require the estimation of a capillary pressure. The estimation of capillary pressure requires the knowledge of liquid contact angles with the porous material. This paper demonstrates the use of liquid extrusion for estimating the liquid−porous medium contact angle. It then demonstrates the estimation of the advancing and receding contact angles for the same system with a modified inclined-plate technique. In this technique, a critical drop mass is experimentally estimated, at a fixed plate tilt angle, as compared to estimating the critical tilt angle for a fixed drop mass. Comparison between the contact angles measured by these techniques shows that the inclined-plate technique gives lower receding and higher advancing contact angles. It is concluded that higher surface roughness of the coated inclined plate is the cause of the above discrepancy and that the liquid-extrusion-based technique yields the better estimate of the liquid−porous material contact angle. This paper also demonstrates that surfactant solutions can be used in liquid extrusion methods, provided their concentration is high enough to ensure that the “extruded” liquid surface tension does not change from its original value.