Interpreting deformation behavior in pharmaceutical materials using multiple consolidation models and compaction energetics

Abstract

Tableting behavior is often characterized using qualitative analyses of compactibility and compressibility measurements. More quantitative methods use consolidation models to estimate parameters indicative of the predominating deformation mechanism exhibited by a material. It will be shown that a concerted approach, using multiple consolidation models and mechanical energy analysis, presents a more reliable way of evaluating the relative plasticity of pharmaceutical materials and identifying complicating behaviors. Force versus displacement data for compact formation, porosity versus pressure and tensile strength data for ejected compacts were collected with a single instrument. The porosity and tensile strength data were analyzed using two relatively new models and the results were compared to three more classical models. Additionally, the mechanical work measurements were used to interpret the consolidation model predictions. Although the individual models are susceptible to a number of errors, complications and invalid assumptions, confidence can be gained when diverse models provide similar predictions. Disagreement between the model predictions can be taken as a sign of atypical behavior that should be further investigated by looking at the material’s mechanical energetics. Finally, the use of work energy associated with compression and decompression as an initial measure of plasticity is supported.

Keywords::

• Powder compaction
• tableting physics
• consolidation modeling
• deformation mechanism
• pharmaceutical excipients

Declaration of interest: I.S.B gratefully acknowledges the University of Iowa Graduate College, the American Foundation for Pharmaceutical Education (AFPE) and J. Keith Guillory and friends for their financial support during this work.