Density is an important material property for evaluating, or developing a tablet formulation. In-die compressibility data can be obtained using a small amount of powder with the help of a compaction simulator. However, compacts undergo volume expansion upon ejection from die. Therefore, accurate out-of-die compressibility profiles cannot be directly obtained from the in-die data. By splitting the tablet elastic recovery into three components (in-die axial, out-of-die axial, radial), we have shown that the in-die elastic recovery is linearly dependent on the compaction pressure within the range investigated, and the out-of-die elastic recovery is a material constant. Hence, we have developed a two-step data treatment (the Hirschberg-Sun approach) for deriving an accurate out-of-die compressibility profile from in-die and out-of-die data of two tablets compressed at a low and a high compaction pressure. The broad applicability of the approach was verified with a larger number of diverse materials.
Bibliographical noteFunding Information:
The authors thank Jiangnan Dun and Else Holmfred for providing the compaction profile data used in this study. C. Hirschberg acknowledges Innovation Fund Denmark (Project: High Quality Dry Products with Superior Functionality and Stability – Q-Dry; File-No: 5150-00024B) for financing her PhD project. Furthermore, C. Hirschberg acknowledges the Faculty of Health and Medical Sciences at the University of Copenhagen for financial support during her stay in Minnesota, during which this work was conducted.
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- Compaction simulator
- Elastic recovery
- Tablet density