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D2873-94 – Standard Test Method Technical Guide
🛠️ Scope and Principle of Mercury Intrusion Porosimetry
ASTM D2873-94 (Reapproved 1999) outlines the standard test method for determining the interior pore volume and apparent pore diameter distribution of porous poly(vinyl chloride) (PVC) resins. The method relies on the principle of mercury intrusion porosimetry, where mercury, a non-wetting liquid, is forced under increasing pressure into the open pores of a resin sample. The sample is placed in a calibrated, graduated penetrometer. By measuring the volume of mercury intruded as a function of the applied hydrostatic pressure, a complete pore volume and size profile can be constructed.
📊 Key Measured Properties and Calculations
The primary value calculated by this method is the interior pore volume, expressed in cubic centimeters per gram (cm³/g). This is defined as the volume of mercury intruded between the point of demarcation—which separates inter-particle void filling from true interior pore filling—and the maximum applied pressure. The apparent pore diameter (D) at any given pressure is calculated using the Washburn relationship as adapted for mercury and the contact angles typical for PVC:
D = 1207 / PkPa
where D is the apparent pore diameter in micrometers. This allows the direct conversion of a pressure-volume curve into a pore size distribution.
| 🎯 Applied Pressure (kPa) | 📏 Minimum Apparent Pore Diameter (µm) |
|---|---|
| 390 | ~3.1 (Demarcation for typical 100 µm resins) |
| 21,000 | 0.058 |
| 35,000 |