The study of granular agglomeration mechanism

The purpose of this study was to determine the effects of the properties of different binders on the granular agglomeration mechanism for the fabrication of pharmaceuticals. The raw materials included calcium carbonate powders with an average particle size of 32–75 μm and four different grades (4000, 6000, 8000 and 10,000) of polyethylene glycol (PEG) used as binders. The raw material was mixed with the binder in a high shear mixer. The surface structure of the granules was analyzed by low vacuum scanning electron microscope (LV-SEM) examination. Three major agglomeration mechanisms are discussed in this study: nucleation, consolidation and coalescence. The results showed that the agglomeration growth rate increased with increasing binder viscosity during the nucleation stage, but the exact opposite phenomenon occurred in the consolidation stage. Observation of the granular surfaces showed the surfaces to be full of fine powder in the nucleation stage, but PEG crystals appeared on the surface in the consolidation stage. During the coalescence stage, the granules grew quickly due to collisions and the surface structures of the granules became full of binders, as can be seen from the LV-SEM photographs.

Graphical abstractWe observed the low vacuum scanning electron microscope photographs of surface structures of granules, using different initial liquid ratios, (a) 0.15, (b) 0.175, (c) 0.2 and (d) 0.225 w/w. The results show that the surface structures of the granular materials with higher initial L/S ratio were smoother than those with lower initial L/S ratio at the coalescence stage.Figure optionsDownload full-size imageDownload as PowerPoint slide