DEGREE OF PELLET DEFORMATION DURING COMPACTION AND ITS RELATIONSHIP TO THE TENSILE-STRENGTH OF TABLETS FORMED OF MICROCRYSTALLINE CELLULOSEPELLETS

The degree of deformation and densification of pellets during compress ion have been quantified. The relationship between the degree of defor mation of the pellets and their compactability were also studied. Two sets of pellets of microcrystalline cellulose, showing a marked differ ence in intragranular porosity, were prepared by extrusion-spheronizat ion. The pellets were mixed with a lubricant and compacted at a series of applied pressures. The individual pellets were retrieved after com pression by tablet deaggregation and the porosity (densification behav iour) 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 wa s almost non-existent during the compression for both sets of pellets. The low porosity pellets showed only limited local permanent deformat ion during compression and the pellet porosity was unaffected by the c ompression. The high porosity pellets showed both a high compression-i nduced change in shape and a marked decrease in pellet porosity. Tensi le strength values of tablets of unlubricated pellets indicated that a marked bulk structure deformation of the pellets was necessary for th e formation of intergranular contacts of a high bonding force in the c ompact.