The use of mercury porosimetry in assessing the effect of different binders on the pore structure and bonding properties of tablets.

This study investigated the effect of binders with different deformability characteristics on the pore structure of tablets composed of binary mixtures. The pore structure was evaluated using mercury porosimetry. The pore size distribution in tablets of both individual components and binary mixtures indicated that the pores in pure binder tablets appeared not to exist to the same degree in composed tablets and were therefore unlikely to substantially contribute to the pore structure. It is therefore suggested that, because the binder undergoes extensive deformation and shearing during compaction, it will exist as relatively small lumps or aggregates or even primary particles that are located between the compound particles. Most of the pores in the binary tablets studied were thus found between particles of the compound and the binder phase. The most deformable binder, polyethylene glycol 3000, had the greatest effect on pore structure, reflected in the greatest increase in tablet strength. An attempt was also made to use mercury porosimetry data to qualitatively assess the effect of a binder on the dominating bond types in a tablet. The results indicated that addition of a binder caused a decrease in the probability of forming solid bridges.