Rate-dependent mechanical properties of granulated pharmaceutical powder formulations

Pharmaceutical tablets are formed using formulations consisting of ingredients such as filler, binder, disintegrant, and active pharmaceutical ingredients. These ingredients are granulated followed by compaction. In the present study, the granules were formed using 5 and 10% binders. These granulated formulations were tested to determine mechanical properties using a medium pressure (<10MPa) flexible boundary cubical triaxial tester. Hydrostatic triaxial compression and conventional triaxial compression tests were conducted at 10 and 20MPa/min loading rates. Fundamental elastic, elastoplastic, and rate-dependent properties such as bulk modulus, compression index, spring-back index, shear modulus, and failure stress were determined from these tests. Some of the key findings were bulk modulus, compression index, and spring-back index increased with pressure. Shear modulus and failure stress increased with confining pressure; Bulk modulus increased with binder content at 10MPa/min while decreased at 20MPa/min loading rate; bulk modulus increased with loading rate. Spring-back index increased with binder content.