Influence of the Punch Speed on the Die Wall/Powder Kinematic Friction During Tableting.

Influence of the compaction speed on the final tablet properties is an important challenge during the scale-up of a solid dosage form. This strain rate sensitivity is generally attributed to the time dependent deformation behavior of the powder. In this work, we studied the influence of the speed on another important factor during compaction: friction between the tablet/powder and the die. An original experimental methodology was developed to study the evolution of the kinematic friction coefficient between the tablet and the die as a function of the sliding speed of the tablet on the die wall. This methodology made it possible to separate the speed used to make the tablet from the speed used to measure the friction coefficient. Results indicate that the kinematic coefficient of friction increases with the sliding speed following a logarithmic trend. This trend was observed for 4 different pharmaceutical excipients. Moreover, it was proved that the speed dependency is an intrinsic property of the friction between a tablet and a die lubricated using magnesium stearate.