physics of tablet compression

1. SUBMITTED TO:
Dr. Yasmeen Sultana

2. Content
1. Introduction
2. Mechanism of tablet compression
 Particle rearrangement
 Deformation
 Fragmentation
 Bonding
 Deformation of solid bonding
 Decompression
 Ejection
3. Problem during ejection

3. INTRODUCTION
• COMPRESSION: Compression means a reduction in the
bulk volume of a material as a result of the removal of the
gaseous phase (air) by applied pressure.
• COMPACTION: Compaction of powder is the general term
used to describe the situation in which these materials are
subjected to some level of mechanism force.
The physics of compaction may be simply stated as “the
compression and consolidation of a two phase (solid-gas)
system due to the applied force’’

4. COMPRESSION COMPACTION

5. • CONSOLIDATION: An increase in the mechanical strength of the
material resulting from particle or particle interaction
• Consolidation Process
cold welding: When the surface of two particles approach each
other closely enough their free surface energies result in strong
attractive force.
Fusion bonding: Contact of particles at multiple points upon
application of load, produces heat which causes fusion or melting. If
this heat is not dissipated the local rise in temperature could be
sufficient to cause melting of the contact area of the particles.

6. MECHANISM OF TABLET
COMPRESSION

7. PARTICLE REARRANGEMENT
• Generally it occures at low pressures.
• It depends on particle size of distribution and shape.
• Reduction in relative volume of powder bed into closure
packing structures.
• the granules flow with respect to each other with the final
particles entering the void between the larger particles and
the bulk density of the granulation is increased.
• As pressure increases , relative particle movement
becomes impossible , inducing deformation.

8. Punch and particle
movement at low
pressure
Fines enters the voids of
larger particles
Rearrangement occurs

9. DEFORMATION
• When the particles of the granulation are so closely
packed that no further fillings of the voids can occur , a
further increase of compression force causes
deformation at the point of contact.
• change in the shape of material occurs.
• At a certain point , the packing characteristics of the
particles, reduced space or porosity of inter-
particulate friction will prevent any further
rearrangement of particles

10. 1. ELASTIC DEFORMATION
Removal of upload act like rubber comes to original
place, usually all solids undergo deformation
example: Acetyl salicylic acid
2. PLASTIC DEFORMATION
They would not come back to its original volume,
completely reduction in bulk volume.
example: Sucrose

12. FRAGMENTATION
• Under high pressure the deformed particles may fragment
resulting in new clean surfaces that have potential bonding
areas.
• Fragmentation leads to further densification with the
infiltration of the smaller particles in the voids.
• The mechanism of fragmentation and plastic deformation
are not independent because both the phenomena modify
particle size distribution.
• With some materials fragmentation doesn’t occurs because
the stresses are released by plastic deformation.

13. Fragmentation do not occur when applied
stress:
•Is balanced by a plastic deformation.
•Change in shape
•Sliding of groups of particle (viscoelastic flow)

14. BONDING OF PARTICLES
 THE MECHANICAL THEORY:
 It occures between irregularly shaped particles .
 Also Increases the number of contact points Between the particles
 The mechanical theory proposes that under pressure the individual
particles undergo Elastic / Plastic Deformation & that the Edges of
the particle intermesh deforming a mechanical Bond.
 Mechanical interlocking is not a major mechanism of bonding in
pharmaceutical tableting.

15.  INTERMOLECULAR THEORY
 The Molecules at surface at the surface of solids have unsatisfied
forces which interact with the other particle in true contact
 Under Pressure Molecules in true contact between new clean
surface of the granule are close enough so that vanderwal forces
interact to consolidate the particles.
 Material containing plenty OH group may also creat hydrogen bond
between molecule.

16. DEFORMATION OF THE SOLID
BODY
• On further increases of the pressure , the non-
bonded Solid is consolidated towards a
limiting density by plastic/elastic deformation.

17. EJECTION
Rising of lower punch
Continuation of residual die wall pressure
Energy expansion due to die wall friction.
Removal of tablet relief of lateral pressure
2 to 10% increase in volume of the portion removed

18. PROBLEM DURING
DECOMPISSION/EJEC
TION
•Capping: deep concave
punches may expand radially,
while the cylindrical part
cannot
•Lamination : Elastic
expansion of some particles
and divided in layers
•Sticling: too much adhesion
on the punch