MERCURY POROSIMETRY STUDIES .2. APPLICATION OF MERCURY POROSIMETRY TO POROUS POLYMER POWDERS

Two experimental methods are outlined for the separation of the inter- and intraparticle intrusion volumes of porous powders. The first of these relies upon the control of interparticle bed packing by mounting the particles upon a transparent adhesive substrate. The pressure at which interparticle penetration occurs (critical pressure) is measured by observing the penetration process directly in a microscope pressure cell. A mercury intrusion experiment is then run on a similarly mounted sample and the value of the critical pressure obtained previously used to define the interparticle volume. In the second method, the critical pressure is determined by running a mercury intrusion experiment on a powder sample whose intraparticle volume has been filled with a wetting liquid-dioctyl phthalate (DOP). This technique depends upon the observation made previously in Part I of this series that bed depacking rather than bed penetration is the initial step of the penetration process. Total intraparticle volumes determined by both of these methods were compared with those obtained by the uptake of a wetting oil (DOP). Although an excellent degree of correlation was observed between the two methods, the DOP uptake values were found to be high by a constant amount. This was demonstrated to be due to oil retained in the interparticle volume. The values of critical pressure determined in this study indicate that the filling of the interparticle voids in a mercury intrusion experiment may not correspond to any feature observed in the penetration curve. Thus it is necessary to determine this quantity separately. © 1979.