Degree of pellet deformation during compaction and its relationship to the tensile strength of tablets formed of microcrystalline cellulose pellets

The degree of deformation and densification of pellets during compression have been quantified. The relationship between the degree of deformation of the pellets and their compactability were also studied. Two sets of pellets of microcrystalline cellulose, showing a marked difference in intragranular porosity, were prepared by extrusion-spheronization. The pellets were mixed with a lubricant and compacted at a series of applied pressures. The individual pellets were retrieved after compression by tablet deaggregation and the porosity (densification behaviour) and dimensions (deformation behaviour) of the retrieved pellets were determined. Tensile strength of compacts prepared of unlubricated pellets was also determined. The incidence of pellet fragmentation was almost non-existent during the compression for both sets of pellets. The low porosity pellets showed only limited local permanent deformation during compression and the pellet porosity was unaffected by the compression. The high porosity pellets showed both a high compression-induced change in shape and a marked decrease in pellet porosity. Tensile strength values of tablets of unlubricated pellets indicated that a marked bulk structure deformation of the pellets was necessary for the formation of intergranular contacts of a high bonding force in the compact.