RHEOLOGY OF PHARMACEUTICAL GRANULATIONS

The rheological transformations that take place when granulating fluid is added to pharmaceutical powders were monitored by means of a laboratory scale (.apprx. 50 g amounts) torque rheometer. The 3 formulations studied, based on lactose, sulfadiazine and benoxaprofen, had common characteristics in that each passed through a granulation peak of a maximum torque. In the zone immediately before the peak the granules were growing, while after it the material had properties of a cohesive, viscoelastic mass. The rheological state of the material under process is not specified by a single torque reading, but by the rheological history of the granulation.