Closed die compaction of powders is an extremely important industrial process. It is a mainstay in many North American industries including the $230 billion/year pharmaceutical industry and the $5 billion/year powder metallurgy industry.
Closed die compaction is an inherently anisotropic process with respect to strains, insofar as axial strain is unrestricted while radial strain is zero. However, anisotropy of other green compact (i.e. no post-compaction processing) properties has not been extensively investigated. These “green” properties are of especial importance to the pharmaceutical industry where little post compaction processing of green compacts is done.
The strength anisotropy and permeability anisotropy of three common pharmaceutical powders and one metal powder have been investigated. The powders investigated cover all basic material categories: Metals, ceramics, and polymers.
The anisotropy trends correlate with material category and particle shape. Computer modeling of particles undergoing closed die compaction provides insight into the possible failure modes of ductile and brittle particles as well as the flow of air through the resulting matrix. Extrapolation from the modeling is consistent with the experimental anisotropy data.
Scanning electron microscopy of failure surfaces for ductile powders shows clear morphology differences consistent with the strength anisotropy trends. The shape of the force/displacement curves from tensile testing of the ductile powders also correlates with the strength anisotropy trends. In addition, the shape of the force/displacement curves appears to reflect the underlying ductile or brittle nature of the material.
Back to Graduate Student Competition
Back to SES Abstracts
Back to The 41st Annual SES Technical Meeting