The tensile strength of bilayered tablets made from different grades of microcrystalline cellulose.

The aim of this work was to determine the tensile strength of bilayered tablets made from different grades of microcrystalline cellulose. While these grades are chemically identical, they differ significantly in their particle size distribution and in their mechanical properties such as Young's modulus of elasticity. Tablets were produced in the shape of beams of similar dimensions using uniaxial compression, and solid beams made from one material only were compared with bilayered beams made from various combinations of powders. It was found that in the production of layered tablets it is important for the purpose of quality assurance and control that the upper and lower layer of the compact can be identified. Otherwise, tensile strength measurements will result in large variability depending on which layer faces upwards during the test. Both particle size and Young's modulus of elasticity influenced the overall strength of layered tablets. If the material forming the lower layer was more elastic, then the beam strength was reduced due to tension introduced into the system, acting especially at the layer interface and potentially causing partial or complete delamination. Larger differences in the particle size of the materials forming the tablet layers resulted in an overall reduced compact tensile strength.