Analysis of densification mechanisms of dry granulated materials

Dry granulation by roll compaction is a continuum manufacturing process to produce granules with improved flowability which can further be easily used in tableting process. However, the granules are non-homogeneous in density and have non-spherical shapes which impact their densification behaviour during die-compaction. The aim of this study was to investigate both the densification mechanism and the failure strength of granules of microcrystalline cellulose (MCC) and mannitol using Cooper-Eaton and Adams models. For both materials, the Cooper-Eaton approach led to the quantification of fractional volume compaction by particle rearrangement and by plastic deformation respectively to explain the difference in densification behaviour of raw material and granules. Moreover, the model showed its ability to capture the effect of granule density and granule sizes and to differentiate the densification mechanisms of MCC as a plastic material and mannitol as a brittle material. The Adams model was used to compute the failure strength of single granule from in-die compression data. The obtained results of the granules were in the range 0.6–1.43 MPa]. However, regarding the effect of granule density, the model showed mixed results indicating that the model is not representative of the studied granules which are not spherical and have a relatively wide range of sizes, nevertheless, the model was derived for near spherical particles with a narrow size distribution.