Compressibilities INDEX

In a more recent study running model formulations having different flow properties on a GKF 400 machine, Heda [50] found that Carr Compressibility Index (Cl) values should be 18flowing powders (CI%>30) were observed to dam up around the... 

Amidon and Houghton [48] completed a comparative study of several common methods of characterizing powder flow. Table 2 contains experimental results for a number of commonly used pharmaceutical excipients. Compressibility index, angle of repose, flow rate through an orifice, and shear cell data are presented. 

In recent years the compressibility index Ci( has become a simple, fast, and popular method of predicting powder flow characteristics [40,42-44,51,52]. Carr [42-44] proposed its use as an indirect measure of bulk density, size and shape,... 

The compressibility index values reported in Table 2 were obtained by tapping powder until a plateau value was obtained. As can be seen from Fig. 4, 2000 to 3000 taps were sufficient to obtain plateau conditions in most cases when the material was relatively free flowing. For poor flowing materials, however, 7000 taps were required. 

Fig. 4 Influence of number of taps on the compressibility index. (Adapted from Ref. 48 with permission of the publisher.)...

Because the compressibility index can be thought of as a measure of the likelihood of arch formation and the ease with which arches will fail [44], and because it can be rapidly completed, it appears to be a useful measure of flow. Obviously, exceptions will occur, and caution should be exercised in its interpretation. As we will dicuss, the compressibility index values reported in Tables 2 and 3 and Fig. 4 are quite consistent with shear cell characterization. 

Trial description Bulk density (g/cm ) Tap density (g/cm ) Compressibility index (%)... 

The Carr Compressibility Index (CI%) is calculated from the loose and tapped... 

In a similar, yet more extensive study, the compaction of compressible sugar was examined for materials preconditioned at different relative humidities. The hardness versus compression profiles (Fig. 21) for these samples show a group of lines whose slope appears to be a function of moisture content. This relationship is also demonstrated in Fig. 22, where the slope is used as a compressibility index. This index is a linear function of moisture content samples with desorbed moisture did not differ from those with adsorbed moisture. 

Elowability 19% (Carr compressibility index) Density (bulk) 1.04 g/cm ... 

Flowability 10.8-11.7g/s for corn starch 30% for corn starch (Carr compressibility index). Corn starch is cohesive and has poor flow characteristics. 

Commonly conducted qualitative tests are the angle of repose, compressibility index or Hausner ratio, and flow rate through an orifice, all of which are thoroughly reviewed in the literature (17). 

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