Compaction Properties of Powders: The Relationship Between Compression Cycle Hysteresis Areas and Maximally Applied Punch Pressures

The consolidation behaviors of various pharmaceutical solids were characterized by investigating the relationship between the calculated hysteresis areas and the maximally applied punch pressures. An Instron universal testing apparatus and an instrumented die were used to generate compression cycle profiles at various maximally applied punch pressures for the materials studied. Based on the profiles obtained, hysteresis areas were calculated for the materials studied as a function of maximally applied punch pressures. Furthermore, model profiles describing the plastic and brittle fracture processes were utilized to derive mathematical relationships between the calculated hysteresis cycle areas and the maximally applied punch pressures. The mathematical relationships derived indicate that a linear relationship between hysteresis areas and maximally applied punch pressures exists for plastic materials, whereas for brittle materials the hysteresis areas are related to the square of the maximally applied punch pressures. Experimental data obtained support the mathematical relationships derived. The goodness of fit to the models derived is used to rank order the consolidation mechanism of various drugs and pharmaceutical excipients.