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## Compressibility Index

Last Update: Oct 24 2017

Compressibility Index is a calculated data other than measured data, it is calculated by the formula:

Compressibility Index = **100(V0****– VF****)/V**0

**V0 **is unsettled apparent volume

**VF **is final tapped volume

angle of repose usp – carr s index –

The Compressibility Index is measure of the propensity of a powder to be compressed as described above. As such it is measure of the powder’s ability to settle, and it permit an assessment of the relative importance of interparticulate interactions. In a free-flowing powder, such interactions are less significant, and the bulk and tapped densities will be closer in value. For poorer flowing materials, there are frequently greater interparticle interactions, and a greater difference between the bulk and tapped densities will be observed. These differences are reflected in the Compressibility Index. In order to obtain compressibility index operator in the lab should first obtain apparent density and second obtain tapped density.

Because the interparticulate interactions influencing the bulking properties of a powder are also the interactions that interfere with powder flow, a comparison of the bulk and tapped densities can give a measure of the relative importance of these interactions in a given powder. Such a comparison is often used as an index of the ability of the powder to flow, for example the Compressibility Index and Hausner Ratio as described below. The Compressibility Index and Hausner Ratio are measures of the propensity of a powder to be compressed as described above. AimSizer Tap Density Tester measures both. As such, they are measures of the powder’s ability to settle, and they permit an assessment of the relative importance of interparticulate interactions. In a free-flowing powder, such interactions are less significant, and the bulk and tapped densities will be closer in value. For poorer flowing materials, there are frequently greater interparticle interactions, and a greater difference between the bulk and tapped densities will be observed. These differences are reflected in the Compressibility Index/Hausner Ratio.

**Compressibility Index Formula** – Calculate by the formula:

100(V0-VF)/V0

V0=unsettled apparent volume

VF=final tapped volume

**Hausner Ratio**=V0/VF

**LABULK 0335 Tap Density Tester is used to measure and calculate the compressibility index of powders.**