compression and consolidation

1. COMPRESSION AND CONSOLIDATION
by
Namile.Shyam Prasad
M.pharm(pharmaceutics)

2. CONTENTS
INTRODUCTION
FUNDAMENTALS OF POWDER COMPRESSION
DERIVED PARA METERS
METHODS
COMPRESSION MACHINES
CONCLUSION
REFERENCES

3. COMPRESSION
the reduction in the bulk volume of a material as a result of
the removal of the gaseous phase (air) by applied pressure
CONSOLIDATION
Involves an increase in the mechanical strength of a material
resulting from particle-particle interactions.
COMPACTION
The compression and consolidation of a 2 phase (solid +
gas) system due to an applied force.

4. FUNDAMENTALS OF POWDER COMPRESSION
 Attractive forces exist between particles vander Waal’s, H-bonding,
Electrostatic consider a number of granules in a die to which a force is
applied

5. DERIVED PARAMATERS
• solid-air interface,
• angle of repose,
• mass volume relationship,
• volume
• density,
• compressibilty

6. Solid-air interface
Cohesion is the attraction between like particle; Experienced by
particles in bulk.
Adhesion is the attraction between unlike particle; Experienced by
particles at surface.

7. Angle of repose
The maximum angle possible between the surface of pile of non-cohesive
(free-flowing) material and the horizontal plane.
Angle of repose is an indication of the flow ability of
the material.

8. Angle of Repose (θ)
θ = tan-1(h/r)
where
h = height of pile
r = radius of the base of the pile
h
Excellent flow ability if θ < 25o
Good flowability if 25o < θ < 30o
Passable flowability if 30o < θ < 40o
Very poor flowability if θ > 40o
r

9. Mass-Volume relationships
VOLUME
1. Open intraparticulate voids-those with in a single
particle but open to the external environment.
2. closed interparticulate voids-those within a single
particle but closed to the external environment.
3. Interparticulate voids-the air spaces between
individual particles.
• True volume (VT)
• Granule volume (VG)
• Bulk volume (VB)
• Relative volume (VR)
VR = VB / VT
VR tends to become unity as all air is eliminated from the mass during the
compression process.

10. DENSITY:
The ratio of mass to volume is known as the density of the material
Types of Density:
• True density (ρT = M / VT )
• Granule density (ρG = M / VG )
• Bulk density (ρB = M / VB)
• Relative density (ρR = M / VR)
M is the mass of powder

11. Compressibility:
The ability of the powder bed to be compressed (under
pressure) and consequently be reduced in volume.
Measuring Compressibility:
Carr’s (Compressibility) Index
= [(VB – VTap) / VB] x 100 ≈ E
where
VB = Freely settled volume of a given mass of powder
VTap = Tapped volume of the same mass of powder ≈ VT
Carr’s (Compressibility) Index
= [(ρTap – ρB) / ρTap] x 100 ≈ E
where
ρB = Freely settled bulk density of the powder
ρTap = Tapped bulk density of the powder ≈ ρT

12. Measuring Compressibility
Excellent flowability if 5 < Carr’s Index < 15
good flowability if 12 < Carr’s Index < 16
Passable flowability if 18 < Carr’s Index < 21
poor flowability if 23 < Carr’s Index < 35
Very poor flowability if 33 < Carr’s Index < 38
Very very poor flowability if Carr’s Index > 40

13. METHODS
Direct Compression

14. Dry Granulation

15. Wet Granulation

16. COMPRESSION MACHINES
Components of compression machines
• Hopper for holding and feeding granulation to be compressed
• Dies that define the size and shape of the tablet
• Punches for compressing the granulation within the dies
• Cam tracks for guiding the movement of the punches
• Feeding mechanisms for moving granulation from the
hopper into the dies

17. Single Punch Machine

18.  Multistation tablet press

19. CONCLUSION

20. Reference
Adolfsson, Å., Caramella, C., Nyström, C., 1998. The effect of
milling and addition of dry binder on the interparticulate bonding
mechanisms in sodium chloride tablets. Int.J. Pharm. 160, 187-195.
Adolfsson, Å., Gustafsson, C., Nyström, C., 1999. Use of tablet
tensile strength adjusted for surface area and mean interparticulate
distance to evaluate dominating bonding mechanisms. Drug Dev.
Ind. Pharm. 25, 753-764.
Adolfsson, Å., Nyström, C., 1996. Tablet strength, porosity,
elasticity and solid state structure of tablets compressed at high
loads. Int. J. Pharm. 132, 95-106.