Assessment of the plasticity of dry granulated particles (mini-tablets) and its relationship to their tabletability

Mini-tablets of different proportions of α-lactose monohydrate (LAC) and microcrystalline cellulose (MCC) were prepared by uniaxial compaction and served as surrogate granules. The inverted Adams coefficient i.e., α ^-1 was derived from bulk mini-tablet compression data and used as an indication of granule plastic deformation. The correlation of the parameter to single granule deformability assessed from uniaxial single mini-tablet compression and macro-indentation hardness was investigated. Furthermore, the relationship between the plastic deformation parameters and the tabletability of mini-tablets were evaluated. An increased MCC concentration resulted in an increased indentation hardness and deformability of the mini-tablets, but no correlation was found between indentation hardness and the α ^-1 coefficient. Thus, the plastic deformation expressed during powder compression showed no relationship to the single specimen indentation hardness and plastic deformability. An increased indentation hardness tended to correspond to an increased tablet tensile strength, while the opposite applied for the α ^-1 coefficient. The trend of increased tablet tensile strength with higher MCC concentration was broken at the highest MCC concentration, i.e., for mini-tablets showing very limited fragmentation. It was concluded that granule plastic deformation is a key property for granule tabletability. It is suggested that granule plastic deformation should be assessed during granule engineering.