Compression and Compaction

This presentation includes the detail information about the physics of tablet compression and compaction, Compression, Effect of friction, distribution of forces, compaction profiles,solubility.

1. COMPRESSION AND COMPACTION Mr. Gaurav Shriram Pat il M PHARM PHARMACEUTICS H R PATEL INSTIUTE OF PHARMACEUTICAL EDUCATION AND RESEARCH, SHIRPUR DEPARTMENT OF PHARMACEUTICS / HRPIPER 6/5/2021 Gaurav Patil 1

2. Contents Introduction Physics of Tablet Compression Process of Tablet Compression Compaction Equation Forces involve in compression Effect of friction Distribution of Forces Compaction profiles Solubility Conclusion References 6/5/2021 Gaurav Patil 2

3. Introduction Tablets constitutes of almost 70-80% of the all dosage forms. Tablets are generally manufactured by 3 main processes. Compaction represent one of the most important unit operations in the pharmaceutical industry. Compaction is the situation in which materials are subjected to some level of mechanical force. The physics behind the compaction is stated as the compression and consolidation of the two phase system due to applied force. While considering the compaction and compression of tablets we had to taken the properties of powder into the consideration as they are involve in the process of the compression and compaction. 6/5/2021 Gaurav Patil 3

4. Derived properties of powder: Volume, density, porosity, Flow properties, angle of repose etc., help in quantification of important variables . Definitions: What is Compression: Compression means reduction of bulk volume of material as a result of the removal of gaseous phase (air) by applied pressure. What is Consolidation: Consolidation is an increase in mechanical strength of material resulting from particle-particle interactions . What is Compaction: Compaction of the powder is the term is used to describe the situation in which the materials are subjected to some level of mechanical forces. Compaction =compression + consolidation of two phases (solid-gas) on application of force. 6/5/2021 Gaurav Patil 4

5. Physics of Tablet Compression: Steps involved in the compression of Tablet. Transitional repacking or particle rearrangement. Deformation Fragmentation Bonding (here removal of process) Deformation of solid body Ejection. 6/5/2021 Gaurav Patil 5

6. Chart showing the steps and process behind the tablet compression 6/5/2021 Gaurav Patil 6

7. Process of Tablet Compression: 1. Transitional Repacking or Particle rearrangement: When a powder is compressed initially the particles are rearranged under low compaction pressures to form a closer packing structure. The finer particles enter the voids between the larger ones and give a closer packing arrangement. In this process, the energy is evolved, as a result of inter particulate friction and there is an increase in the amount of particle surface area capable of forming inter particulate bonds. 6/5/2021 Gaurav Patil 7

8. 2. Deformation: When the particles of granulation are so closely packed that no further filing of voids can occur, a further increase in the compression force causes deformation at that point of contact Change in shape of material occurs. At certain points the packing characteristics of the particles reduced space or porosity of inter-particulate friction will prevent any further rearrangement of particles. At this point further reduction in the compact volume results in elastic or plastic deformation. 6/5/2021 Gaurav Patil 8

9. 3.Fragmentation: As compression force increases deformed particles start fragmentation due to high load, particles breaks into smaller fragments leading to formation of new bonding areas. The fragment undergo densification with infiltration of small fragments into voids. Some particles undergo structural break down called as brittle fracture. 6/5/2021 Gaurav Patil 9

10. 4.Bonding of Particles: After the fragmentation of the particles, as the pressure increases, formation of new bonds between the particles at that contact area occurs. The hypothesis favoring for increase in mechanical strength of bed of powder when subjected rising compressive forces can be explained by following theories. Liquid surface film theory Intermolecular theory The mechanical theory. Liquid surface theory: This theory attributes bonding to the presence of a thin liquid film which may be the consequences of fusion or solution at the surface of the particles. This theory is a combination of Solid bridge, Hot welding and Cold welding theory. The Mechanical Theory : It occurs between irregularly shape particles and increase no of point of contact between the particles. This theory proposes that under pressure the individual particles undergo elastic or plastic deformation and edges of particle intermesh deforming a mechanical bond. 6/5/2021 Gaurav Patil 10

11. 5. Deformation of the solid body : As the applied force /pressure is further increased the bonded solid is consolidated towards a limiting density by plastic/ elastic deformation of the tablet within the die. 6. Ejection: The last stage in compression cycle is ejection from die. The force necessary to eject a tablet involves the distinctive peak force required to initiate ejection, by breaking of die wall– tablet adhesion. The second stage involves the force required to push the tablet up the die wall, and the last force is required for ejection. 6/5/2021 Gaurav Patil 11

12. Compaction Equations: 1.Heckel equation : The Heckel equation is based on the assumption that densification of the bulk powder under force follows first-order kinetics. The Heckel equation is expressed as; In [1/1-D] = KP +A Where, D is the relative density of the tablet (the ratio of tablet density to true density of powder) at applied pressure P, and K is the slope of straight line portion of the Heckel plot. 6/5/2021 Gaurav Patil 12

13. 2.Kawakita equation : The basis for Kawakita equation for powder compression is that the particles are subjected to compressive load in equilibrium at all stages of compression, so that the product of pressure term and volume term is constant. Pa/C = 1/ab +Pa/a Where, Pa= Applied pressure, a= degree of volume of reduction for bed particles. b= Constant inversely proportional to yield strength. C= Degree of Volume of reduction. 6/5/2021 Gaurav Patil 13

14. Forces involves in the Compression 1.Frictional forces Inter-particulate friction Die wall friction 2 . Distribution force 3 . Ejection Force: The force necessary to eject the finished the tablets. 4. Radial Force. 6/5/2021 Gaurav Patil 14

15. Effect of Friction Two major component to the frictional force. 1.Inter-particulate friction Occur due to particle-particle contact and more significant due at low applied load. These frictional effect is reduced by addition of glidants like colloidal silica or corn starch. 2. Die wall friction. Die wall friction occurs from material pressed against die wall and moved it down. It is expressed as mw the coefficient of die wall friction. This effect is reduced by the addition of lubricants. Eg . Waxes, Stearic acid, PEG. 6/5/2021 Gaurav Patil 15

16. Distribution of Forces Distribution Force: The fundamentals of tableting have been carried out on single station press or even on isolated punch or punch with hydraulic press. When the force is being applied to top of cylindrical powder mass, the following basic relationship is applies, since there must be an axial balance of forces. FA=FL+FD Where, FA= Force applied to upper punch and FD= force transmitted to lower punch & FD= Reaction at die wall due friction at surface. 6/5/2021 Gaurav Patil 16

17. Compaction Profiles Compaction profiles are hysteresis curve that establish the relationship between the axial pressure and radial pressure. In compaction cycle two forces are considered: Axial Force: This is the vertical component applied by upper punch during the compression. Radial force: This is the horizontal component observed in die wall , when powder mass attempt to in the die wall. 6/5/2021 Gaurav Patil 17

18. Compression phase: OA- Repacking of powder or granules. AB- Represent elastic deformation which continues upto B BC- It represent plastic deformation and brittle fracture and point C indicates maximum compression force. Decompression Phase: CD- Represent elastic recovery. DE- Represent recovery from plastic deformation. E- Represent residual force, hold compact in die sides. Ejection force must be greater than residual force. 6/5/2021 Gaurav Patil 18

19. How they are measured: It is analysed by the compaction simulators, these are attached to the which collect or measure the data from the forces on punches, displacement of punches, die wall friction, ejection force, and temp change. Types of compaction profiles: 1. Force- time profile 2. Force displacement profile 3. Die wall force profile 6/5/2021 Gaurav Patil 19

20. Applications of compaction profiles These can be used to monitor the compaction cycle. Provide information regarding the radial transmission of applied force to the die wall. Helps in calculating ejection force and lubricant requirements. Compaction profiles give good assessment of elastic component of the powder. 6/5/2021 Gaurav Patil 20

21. Solubility Solubility can be defined as spontaneous interactions of two or more substances to form homogenous molecular dispersion. Or Concentration of Solute in a saturated solution at constant temperature. Importance of Solubility: Therapeutic effectiveness of the drug is depends on bioavailability of the drug and hence it ultimately depends on the solubility. Imp to achieve desired concentration of drug molecule into the systemic circulation. Important in respect to the preformulation studies. 6/5/2021 Gaurav Patil 21

22. Conclusion Compaction and compression are an integral processes for the manufacture of tablets, and it is pertinent to understand the underlying physics of compaction. Complete understanding of compaction physics still eludes us, many variables such as inherent deformation behaviour of drugs/excipients, solid state properties, and process parameters are known to affect the final attributes of tablets. Various mathematical equations have been used to describe the process of compaction are played integral role in overall process. Check out this short and simple video of tablet compression here 6/5/2021 Gaurav Patil 22

23. References Banker GS, Anderson NR. Tablets, In: Lachman L, Liberman HA, Kanig JL, editors. The Theory and Practice of Industrial Pharmacy, 3rd ed., Bombay, Varghese Publishing, 1976. Marshall K. Compression and consolidation of powdered solids, In: Lachman L, Lieberman HA, Kanig JL, editors. The Theory and Practice of Industrial Pharmacy, 3rd ed. Bombay, Varghese Publishing, 1987. Images an Video: Source Google and Wikipedia . Textbook of the theory and practice of industrial pharmacy by Lachman. 6/5/2021 Gaurav Patil 23

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