Comparison between mechanical properties of dry blended and granulated pharmaceutical powder formulations

Pharmaceutical tablets are formed using various powder ingredients such as filler, binder, disintegrant, and active pharmaceutical ingredients (APIs). Tablets are formed either by dry blending the above ingredients or wet granulation of the powder mix followed by compaction. In the present study, the powder ingredients were dry blended using a manual blender and granulated using a high shear mixer. The granules were oven dried and sieved to get the desired size range. Both the dry blend and granulated powders were tested to determine mechanical properties using a medium pressure flexible boundary cubical triaxial tester (CTT). Hydrostatic triaxial compression (HTC) tests were conducted at pressures upto 10 MPa. The data obtained from the HTC tests used for determining the various fundamental elastic, elastoplastic, and rate-dependent properties such as bulk modulus, compression index, and spring-back index. The bulk modulus increased linearly in all cases with pressure. At 10 MPa/min loading rate, the bulk modulus value increased with binder content. The increase in bulk modulus values were more in case of granulated powder formulation as compared to dry blended powder formulation. In case of dry blended powder formulation, the compression index values increased with pressure in all cases. At 10 MPa/min loading rate, for dry blended powder formulation the compression index generally decreased with binder content. In case of granulated formulation the compression index increased with binder content. In general, the compressibility of the powder was increased by granulation. The spring back index increased with increase in pressure in all cases. In case of dry blended formulation, at 10 MPa/min loading rate, the spring-back value decreased with binder content. In case of granulated powder formulation, the spring back index for 10% binder content was higher than for 5% binder content. Granulation decreased the spring-back index of the powder formulation.