The normalization of the solid fraction of particulate compacts

Abstract

Meaningful comparison of the compressibility and compactibility of different powder materials cannot be made using the solid fraction as a yardstick for comparison, due to the different ranges of solid fraction over which different materials consolidate. Consequently, the solid fraction has been normalized as follows: P = ( Θ rc − Θ rf)/(1 − Θ rf), where Θ rc is the solid fraction of the compact at a given consolidation state and Θ rf is a reference solid fraction marking the begin of interparticle bond formation. This work evaluates comparatively the appropriateness of the relative tap density, Θ rT, (which is the tap density expressed as a ratio of the true density) and the solid fraction, Θ ri, at the point where the punch forces begin to increase and subsequently remain above the noise level of the load transducers, as reference densities. It was deduced that. Θ ri is more appropriate than the tap density as the reference density. In the event where Θ ri cannot be determined, the relative tap density may be used for noncohesive materials; it cannot however be used for cohesive materials. It was also shown that Θ ri is independent of compression speed.