4.1physics of tab compression

physics of tablet compression

1. Physics of tablet compression SUBMITTED BY: Gaurav M.Pharma (pharmaceutics) Jamia Hamdard SUBMITTED TO: Dr. Yasmeen Sultana

2. Content Introduction 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. 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

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

10. 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.

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

12. 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 .

13. 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.

14. 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.

15. EJECTION

16. PROBLEM DURING DECOMPISSION/EJECTION 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