Powder flow properties are affected by particle size, shape, density, and forces like friction and cohesion between particles. Tests like angle of repose, Carr's compressibility index, and Hausner's ratio are used to evaluate a powder's flowability, with lower angles and ratios generally indicating better flow. The angle of repose is determined by allowing powder to flow through a funnel onto a surface, with flow classified as excellent below 25 degrees and very poor above 40 degrees. Carr's index and Hausner's ratio both compare a powder's bulk and tapped densities to characterize flow, with better flow indicated by lower percentage values.

1. FLOW
PROPERTIES
OF POWDER
RAHUL PAL
B.PHARM 5th SEM
(Industrial Pharmacy 1st )

2. JensMartensson
“Powders may be free flowing or sticky.”
Flowabilty of powder & chemical stability depends on the habit & internal structure of
a drug.
❖ Habit - Description of the outer appearance of a crystal.
❖ Internal Structure – Mainly depends on the environment for growing crystals.
• Powder flow property can affected by the change in particle size, shape & density.
The flow property depends upon following –
❑ Force of Friction – Generated by two surfaces that contacts & slide against
each other, angle & position of object mainly affected.
❑ Cohesion Force – Between one particle to another.
Example – Caking tendencies within a bag after shipping or storage time or
talcum powder.
❑ Powder Flow Properties
2

3. JensMartensson
Test to evaluate the flowability of a powder –
❑ Determination of Powder Flow Properties
3
1
➢Angle of Repose
2
➢Carr’s Compressibility
Index
3
➢Hausner’s Ratio

4. JensMartensson
• “A technique for estimating the flow properties of powder determined
by allowing a powder to flow through a funnel & fall freely on to a
surface.”
Other methods to determinding the angle of repose-
 Static angle of repose.
 Fixed funnel method.
 Fixed cone method.
 Kinetic & dynamic method.
 Rotating cylinder method.
❑ Angle of Repose
4

5. JensMartensson
• The height & diameter of resulting are measured –
Where ,
h = Height or powder cone (pile).
r = Radius of circle.
Continue…
5
Angle of repose
(Degree)
Types of flow
<25 Excellent
25-30 Good
30-40 Passable
>40 Very poor
𝜽 = tan-1
𝒉
𝒓

6. JensMartensson
“One hundred time of the ratio of the different tapped density & bulk
density to the tapped density.”
➢Bulk Density = Ratio of weight to volume of sample
➢Tapped Density = Ratio of weight of sample to volume after trapping
a measuring a cylinder 500 times from a two inches height.
• It may be also known as “Percentage Compressibility.”
❑ Carr’s Compressibility Index
6

7. JensMartensson
% Carr’s Index = (Tapped density – Bulk Density) /Tapped Density x 100
% Carr’s Index = (TD – BD) /TD * 100
7
%Carrs Index Type of Flow
< or =10 Excellent
11-15 Good
16-20 Fair
21-25 Passable
26-31 Poor
32-37 Very poor

8. JensMartensson
• “Hausner’s is the ratio of tapped density to bulk density.”
❑ Housner’s Ratio
8
Housner’s ratio =Tapped Ratio / Bulk Ratio
H.R =TD/BD
Hausner’s Ratio Flow Properties
1-1.11 Excellent
1.12-1.18 Good
1.19-1.25 Fair
1.26-1.34 Passable
1.35-1.45 Poor
1.46-1.59 Very poor

9. Thank
You