In the experiment, the porous solid systems are attached to a microbalance and brought into contact with several liquids. Their penetration velocities are determined by the slope of weight versus time plots. A commercial tensiometer can be used for these gravimetric experiments (Fig. 2). The application of this concept was demonstrated for hydrophobic polymer powders (PTFE, polypropylene, polyethylene, polystyrene), for hydrophilic (cellulose) and hydrophobic (PTFE) membranes, for pigments used in powder coatings, for inorganic fillers used in polymer composites and for textile fiber bundles. The solid surface tension values determined by the capillary penetration technique are in good agreement with the γsv values obtained from contact angle measurements on flat and smooth solid surfaces of the same materials.
Fig. 2: A schematic of the experimental set-up for capillary penetration measurements using a commercially available tensiometer.