Dry granulation using roll compaction process : powder characterization and p rocess understanding.

In recent years, dry granulation using roll compaction (DGRC) attracts considerable interest of engineers and researchers, especially in the pharmaceutical industry, due to its distinct feature that no liquid binder is needed. It is generally anticipated that as a size enlarge process, DGRC would improve properties of feed powders (such as flowability and bulk density), but it was also reported that DGRC could cause a reduction in powder compactibility. A wide range of powder properties, such as size, shape, flowability, compactibility and compressibility, were analysed for several pharmaceutical excipients using the state of art techniques. Elastic-plastic properties of single component powders and mixtures were also determined using the Drucker Prager Cap (DPC) model and an example of FEM application was presented. All the properties determined were used to investigate: 1) the prediction of ribbon milling from friability tests and 2) the effect of granule size on die filling and die compaction behaviour of pharmaceutical powders. A new and easy method was developed for predicting fines produced during ribbon milling. An exponential relation between the filling ratio and the shoe speed was found. Furthermore, it is shown that flowability is strongly influenced by the granule size, and there is a decrease in the tensile strength with the increase of the granule size. Additionally, for all the materials analysed a strong correlation between the flow indexes and the critical filling speed was observed and an empirical equation is obtained