(70m) The Analysis of Fracture Surfaces of Bi-Layer Tablets of Microcrystalline Cellulose (MCC) Using Laser Profilometry

The introduction of bi-layer tablets into the pharmaceutical industry has enabled the development of pre-determined release profiles of active ingredients. During production, however, these bi-layer tablets have the tendency to fracture by capping, thought to be caused by internal tensile stresses normal to the plane of fracture. Bi-layered tablets of the widely used excipient Microcrystalline Cellulose (MCC) have been manufactured on site and using a developed tensile stress method have been stressed until fracture. The topography of the fracture surfaces at the interface has been obtained using laser profilometry. The overall geometric shape of the topographic profile has shown to provide insight into the magnitude of stress field that the MCC particles present at the interface have endured. The die wall friction has also shown to have significant implications in the development of bi-layer tablets. Using an unlubricated punch and die set it can clearly be seen that the retardation force of the die wall creates an inherent crack at the interface of the adjacent layers during either the unloading or the more likely ejection stage of the compaction process. This crack will act as a stress concentrator significantly weakening the tablet strength.