title: Evolution of the Die-Wall Pressure during the Compression of Biconvex Tablets: Experimental Results and Comparison with FEM Simulation.
abstract: Capping is a classical manufacturing problem for tablets, which is known to affect more biconvex tablets than flat-faced ones. One reason could be the development of a higher residual die-wall pressure during unloading. Unfortunately, contradictory results were published on the subject. In this work, the evolution of the die-wall pressure during the compaction of biconvex tablets was studied experimentally and using finite element method (FEM) modeling. It was compared with the case of flat-faced tablets. Experimental and numerical results showed that during the compression of biconvex tablet, a lower maximum die-wall pressure and a higher residual die-wall pressure were obtained compared with the case of flat-faced tablet. Moreover, both approaches showed, for biconvex tablets, a temporary increase of the die-wall pressure at the end of the unloading phase. FEM demonstrated that this phenomenon was due to a gradual loss of contact between the punch and the tablet from the side to the center. This complex unloading behavior causes the temporary increase of the die-wall pressure and the development of a shear stress between the convex part and the land of the tablet. This could explain the capping tendency of biconvex tablets.
authors.affiliation: Univ. Bordeaux, CNRS, Bordeaux INP, ENSAM, Bordeaux F-33000, France.
authors.forename: Vincent
authors.initials: V
authors.lastname: Mazel
authors.affiliation: CNRS, Univ. Bordeaux, Bordeaux INP, ENSAM, Bordeaux F-33000, France.
authors.forename: Harona
authors.initials: H
authors.lastname: Diarra
authors.affiliation: Univ. Bordeaux, CNRS, Bordeaux INP, ENSAM, Bordeaux F-33000, France. Electronic address: vincent.mazel@u-bordeaux.fr.
authors.forename: Virginie
authors.initials: V
authors.lastname: Busignies
authors.affiliation: Univ. Bordeaux, CNRS, Bordeaux INP, ENSAM, Bordeaux F-33000, France.
authors.forename: Pierre
authors.initials: P
authors.lastname: Tchoreloff
mesh_terms: D005079:Excipients / Q000737:chemistry; D020342:Finite Element Analysis; D011208:Powders / Q000737:chemistry; D011312:Pressure; D013314:Stress, Mechanical; D013607:Tablets / Q000737:chemistry*; D013678:Technology, Pharmaceutical / Q000379:methods; D013718:Tensile Strength
chemical_list: D005079:Excipients; D011208:Powders; D013607:Tablets
keywords: compression; excipients; powder technology; tablet; tableting