V. Mazel a, H. Diarra a, P. Tchoreloff c.
a Université de Bordeaux, CNRS, I2M Bordeaux, 146 rue Léo Saignat 33000 Bordeaux
Purpose.
Tablets final properties are mainly determined during the compaction process by the evolution of the stresses applied to the powder (axial/radial). Any process or product parameter that influences this stress evolution may have a direct impact on the tablet final properties. In this work, we studied the influence of the friction between the tooling and the powder on the evolution of the die-wall pressure during compaction using flat and concave punches. In addition, effect of internal lubrication on die wall transmission was also studied in order to understand the influence of particle/particle frictions on the stress evolution during compaction.
Methods.
Experimental work was performed on a compaction simulator using both flat and concave punches. An external lubrication device was used in order monitor the tooling/powder friction. Numerical simulation was performed using Finite element method (FEM).
Results.
Increasing the powder/tooling friction promotes an increase in the die-wall pressure during tableting. This is in contradiction with results that can be found in the literature.
For flat punches, the stress evolution is mainly driven by the die/powder friction. On the contrary, for concave punches, changing the punches/powder friction have also a consequence in the evolution of the die-wall pressure.
Study of various levels of internal lubrication also emphasized the importance of particle/ particle frictions on the die wall pressure evolution.
Conclusions.
Friction (powder/powder and powder/tooling), significantly influences the stress evolution during compaction. For concave punches, the influence of the punch/powder friction may have practical consequences in sticking situations.
Vincent Mazel
After studies in fundamental physics, Vincent Mazel prepared a phD in Material Science from the University Pierre et Marie Curie (Paris). After 8 years as an assistant professor at the university Paris-sud, he moved to the University of Bordeaux. He’s now part of the institute of mechanical Engineering at the University of Bordeaux where his teaching activities are focused on pharmaceutical processes for the production of solid dosage forms. His research is focused he studies the application of the tools of mechanics (experimental and numerical) for the understanding of the phenomena occurring during pharmaceutical compression. He’s especially interested in the problems of tablet fracture like capping or lamination.