What is compressibility index and Hausner ratio?
The Carr Compressibility Index and Hausner Ratio are two measures which can be used to predict the propensity of a given powder sample to be compressed, and which are understood to reflect the importance of interparticulate interactions.
What is a compressibility index?
The Compressibility index and Hausner ratio are measures of the propensity of a powder to be compressed as described above. As such, they are measures of the powder ability to settle and they permit an assessment of the relative importance of interparticulate interactions.
How is Hausner ratio calculated?
The Hausner ratio6 expressed as the tap density divided by the bulk density, Hr = ρtap/ρb, and related Carr index,7 CI = 1 − 1/Hr, are used to indicate the flowability of granular powders in a wide variety of industries.
How can determine the flowability of powder?
Some of the most commonly applied methods to measure the flow of powders include: density indices, such as the Carr index and Hausner ratio, powder avalanching, the angle of repose (AOR), flow through an orifice, powder rheometry and shear cell testing.
How is the compressibility index and flowability calculated?
Compressibility Index and Flowability Compressibility Index is a calculated data other than measured data, it is calculated by the formula: The Compressibility Index is measure of the propensity of a powder to be compressed as described above.
How accurately Carr’s Compressibility Index and Hausner ratio?
Since Carr’s index and Hausner ratio are not the intrinsic properties, they may not always give the accurate estimation of the blend flowability Measuring bulk densities will not accurately determine the flow properties. Carr’s index and Hausner ratio will however provide basic understanding of the flow properties of particles
Why does a powder have a low compressibility index?
A free-flowing powder should have a low compressibility index, because the inter-particle forces are not as significant as in a poorly-flowing powder, which implies the value of bulk density is close to that of the tapped density. As a general rule of thumb, a compressibility index of higher than 30% indicates poor powder flow.
Which is a compendial method for powder flowability?
The compendial methods include measurement of angle of repose, bulk density, tapped density, carrs compressibility index or hausners ratio  and another method like FT4 powder rheometer. The FT4 powder rheometer is designed to characterize powders under various conditions in ways that resemble large – scale production environment.