The physical state of binders during the granulation process has a significant impact on the wet granulation process and granule, tablet properties. Li et al. evaluated the physical state of a binder on wet granulation and granule properties using the binary model system. PVP K12 needed a small amount of water to change from glassy to the rubbery/solution state for granule enlargement. On the other hand, HPMC required longer granulation time and more water to reach the solution state [14]. PVP might reach the rubbery/solution state faster compared to the other binders, which caused the granule enlargement with a small amount of water (added water 1.0%, 111 μm). HPMC might not change from glassy to the rubbery/solution state with a small amount of added water (1.0%, 1.5%, 2.0%).
The Hausner ratio of all Met granulates was acceptable (1.13–1.33).
3.2. Compaction analysis
Fig. 1 shows the Heckel plots of Met API and the Met granulates produced with the various binders, and Table 3 shows the summary of the Heckel analysis. The yield pressure and elastic recovery was calculated by the Heckel plots profile (see Section 2.5). For this analysis, the volume of added water was 1.5%. Intact Met API was also evaluated for the comparison. Oleic acid was coated thinly over the punches for prevention of sticking.