Simplifying Johanson’s roller compaction model to build a “Virtual Roller Compactor” as a predictive tool – Theory and practical application

The purpose of the study is to build a “virtual roller compactor” as a predictive tool to assess the roll force (RF)-maximum pressure (Pmax) and RF-ribbon density relationship for pharmaceutical roller compaction. We provided a theoretical basis to demonstrate that, there exists a critical nip angle for a pharmaceutical powder, beyond which the RF-Pmax relationship is insensitive to wall friction angle or effective angle of internal friction. We showed that for most pharmaceutical roller compaction, the critical nip angle is lower than 17 degree, and can be exceeded via wall friction elevation, using rolls with non-smooth surface. Under this condition, the original Johanson model can be substantially simplified to a single equation requiring only one material property (compressibility). By performing manufacturing-scale roller compaction using materials with diverse compressibility, we showed that the simplified, friction angle-free model performed similar to the original Johanson model. It can predict the RF-Pmax and RF-ribbon density relationship well after applying a correction factor. The predictive tool, in the form of a user-friendly graphical user interface, was created based on the simplified model. The tool was adopted for in-house, bench-scale formulation development and scale-up because of its ease-of-use, good predicting capability, and very low material demand.