COMPRESSION AND COMPACTION , physics of tablet compression, compression, consolidation, effects of friction, distribution of forces, compaction profiles, solubility.

1. Masters of pharmacy, Pharmaceutical technology (Pharmaceutics)
Subject- Modern Pharmaceutics (MPH-103T)
Lesion no- 4, Compression and compaction By- Drx JAYESH M.RAJPUT
Points:-
1) 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.
Consolidation:-
Consolidation is an increase in the mechanical strength of a material resulting from particle-particle interactions. It is
an increase in the mechanical strength of the material resulting from particle or particle interaction. (Increasing in
mechanical strength of the mass)
Consolidation process: - 1. Cold welding:- when the surface of two particles approach each other closely enough (e.g.
at separation of less than nm) their free surface energies result in strong attractive force. This process known as cold
welding.
2. Fusion bonding:- contacts 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. Upon removal of load it gets solidified giving rise to fusion bonding and increase the
mechanical strength of mass.
Compaction:-
Compaction of powders is the general term used to describe the situation in which these materials are subjected to
some level of mechanical force. The physics of compaction may be simply stated as “the compression and
consolidation of a two phase (particulate solid-gas) system due to the applied force”.

2. The process of compression:-
Transitional repacking/ particle rearrangement---- deformation at points of contact---- fragmentation and
deformation---bonding---- removal of pressure----deformation of solid bonding----decompression----ejection.

3. Fragmentation and deformation:-
Higher pressure----cracks formation----increase in number of particle----formulation of new surface area.
Fragmentation does not occur when applied stress is balanced by a plastic deformation change in shape sliding of
groups of particle (viscoelastic flow).

4. 3 stages of force necessary to eject a finished tablet.
1- Peak force required to initiate ejection
2- Small force required to push tablet up to die-wall
3- Decline force as tablet emerge from die
2) Effect of friction:-
Two major components to the frictional force:-
1. Interparticulate friction
This arises at particle/ particle contacts and can be expressed in term of a coefficient of Interparticulate friction m1. It is
more significant at low applied loads. Material that reduced this effect are referred to as Glidants, e.g. colloidal silica,
talc, corn starch.
2. Die wall friction
This result from material being pressed against the die-wall and moved down it, it is expressed as mw, the coefficient of
die wall friction. Most tablets contain a small amount of an additive design to reduced die wall friction; such additives
are called lubricants. E.g. magnesium stearate, talc, PEG, waxes, stearic acid.

5. Compaction:- compaction is defined as “compression and consolidation of a two phase system (particulate solid-gas)
due to applied force”
Solubility:- solubility is defined as quantitative terms as concentration of solute in concentration of solute in
concentrated solution at a certain temperature, and in qualitative way it can be defined as a spontaneous interaction of
two or more substance to form a homogeneous molecular dispersion.
Importance of solubility:-
o Therapeutics effectiveness of a drug depends upon the bioavailability and ultimately upon the solubility of drug
molecule
o It is important parameter to achieve desired concentration of drug in systemic circulation for pharmacological
response to be shown
o Any drug to be absorbed must be soluble or present in the form of an aqueous solution at the site of absorption.

6. 3) Physics of tablet compression:-
PHYSICS OF TABLET COMPRESSION Tablet compression physics includes: Transmission of forces during compression
Distribution of forces in tablets The effect of applied pressure on the relative volume of the powder Interparticulate
adhesion and cohesion forces Tablet compression energies Mechanical strength of tablets Detailed description of the tools
used in these studies and working methods. The main criteria for tablet formulations are: To form tablets without sticking
to the punch surfaces and to the die wall, and capping; To compress the tablets with acceptable mechanical properties in
terms of hardness and friability; To meet pharmacopoeia limits for tablet weight variation and content uniformity; To
provide appropriate disintegration time and dissolution rate for the tablets.

8. Generally, internal surface area increases with increasing compression force. This initial increase
is due to fragmentation of granules at relatively low compression force. When compression
force is further increase rebonding takes leads to decrease in free internal surface.
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