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Compression and compaction

The document provides an overview of key concepts related to the compression and consolidation of powder solids in pharmacy, covering definitions, properties of powder, methods for measuring various parameters, and the mechanisms involved in the compaction process. It discusses the significance of angle of repose, mass-volume relationships, force-volume relationships, and the effects of compression forces on tablet formation. Additionally, the document outlines the theoretical equations relevant to understanding the compaction and strength of tablets, as well as techniques to minimize manufacturing issues like capping and lamination.

Health & Medicine◦
11 Department of Pharmacy (Pharmaceutics) | Sagar savale 04/21/16 Sagar KiShor Savale
CONTENTS. Definition. Inherent properties of powder solids. Solid air interface. Angle of repose and flow rates. Mass volume relationship. Process of compression. 2204/21/16 Sagar KiShor Savale
Die wall lubricant. Force and volume relationship. Heckel plot and kawatika equation. Compaction profile. Energy expenditure. Measurement of energy.  transmission of force.  force displacement curve. Strength of tablet and its estimation. References. 3304/21/16 Sagar KiShor Savale
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. 4404/21/16 Sagar KiShor Savale
WHAT IS COMPACTION ? The compression and consolidation of a two phase (solid + gas) system due to an applied force, resulting in the formation of a compact but porous mass of definite geometry. Compaction =compression + consolidation of two phases (solid-gas) on application of force. 5504/21/16 Sagar KiShor Savale
Inherent properties of powder solids Solid –air interfaces. Angle of repose. Fixed funnel and free standing cone method. Tilting box method. Revolving cylinder method. Mass –volume relationships. Methods to mesure volume of powder.  Helium pycnometer  Liquid displacement method (specific gravity bottle method 604/21/16 Sagar KiShor Savale
7 Angle of repose. The maximum angle possible between the surface of pile of the powder and the horizontal plane. (also called as Dynamic angle) 704/21/16 Sagar KiShor Savale
8 METHODS TO MEASURE ANGLE OF REPOSE. a.Fixed funnel and free standing cone method. b.Tilting box method. c.Revolving cylinder method 04/21/16 Sagar KiShor Savale
9 FORMULA FOR MEASURING ANGLE OF REPOSE 1. θ = Tan-1 (h/r) here, h =height of pile r = radius of the base of the pile θ = angle of repose. 2. θ = cos-1 D/ (l1+l2) here, D = diameter of base l1+l2 = the opposite sides Angle of repose Flow property of powder <25 25-30 Excellent Good 30-40 Passable >40 poor 904/21/16 Sagar KiShor Savale
10 CONSOLIDATION INDEX (Carr, % ) FLOW 5-15 EXCELLENT 12-16 GOOD 18-21 FAIR TO PASSABLE 23-35 POOR 33-38 VERY POOR >40 VERY VERY POOR 1004/21/16 Sagar KiShor Savale
11 MASS-VOLUME RELATIONSHIPS. TYPE OF VOIDS OR AIR SPACES:  Open intraparticulate voids-  Closed intraparticulate voids-  Interparticulate voids- 11 Fig:- types of voids and air spaces. 04/21/16 Sagar KiShor Savale
METHODS TO MEASURE VOLUME OF POWDER.  Helium pycnometer  Liquid displacement method (specific gravity bottle method) HELIUM PYCNOMETER Vt = Vc/U1-U2x[U1-Us] Vt = true volume of sample. Vc =true volume of stainless steel spheres. U1=Volume of empty cell. U1-U2=Volume occupied by the std. sample. U1-Us = volume occupied by sample. 121204/21/16 Sagar KiShor Savale
13 Helium pycnometer. 04/21/16 Sagar KiShor Savale
Liquid displacement method. Solvent used are ---e.g., ethyl alcohol ,water, mercury , etc. Pycnometer or specific gravity bottle used. True density= w3/(w4-w2) = (w2-w1)/(w4-w2) w1 = wt. of Pycnometer w2 = Wt. of Pycnometer +sample or glass beads w4 = Wt. ofPycnometerwith powder & filled with solvent w3=w2-w1=Wt. of sample w4-w2=Volume of liquid displaced by the solid 141404/21/16 Sagar KiShor Savale
15 specific gravity bottle 1504/21/16 Sagar KiShor Savale
Tablet Press Machine 1604/21/16 Sagar KiShor Savale
. 17 The process of compression. 17 REMOVAL OF PRESSURE 04/21/16 Sagar KiShor Savale
Deformation • The force required to initiate a plastic deformation is called as yield stress or elastic limit. 181804/21/16 Sagar KiShor Savale
Effects of compression force. 19 INITIALLY REPACKING DEFORMATION 1904/21/16 Sagar KiShor Savale
Transitional repacking/particle rearrangement. 202004/21/16 Sagar KiShor Savale
Fragmentation and deformation. Fragmentation do not occur when applied stress-  is balanced by a plastic deformation. change in shape. sliding of groups of particle (viscoelastic flow). 212104/21/16 Sagar KiShor Savale
22 If, only elastic deformation occurs – Under nonisostatic conditions- Uniaxial relaxation 2204/21/16 Sagar KiShor Savale
Ejection. 2323 Portion under strain caps strain > shear strength. 04/21/16 Sagar KiShor Savale
3 stages of force necessary to eject a finished table, 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. 242404/21/16 Sagar KiShor Savale
Compression and consolidation under high loads. 2525 Thin layer is abrasion resistant but it – Retards air escape during compression. Retards the ingress of liquid media during dissolution. punch Die wall tablet 04/21/16 Sagar KiShor Savale
Die-wall lubrication • Best lubricant has low shear strength & strong cohesive tendencies. • Lubricant forms a film of low shear strength at the interface between tabletting mass & die-wall. 2626 LUBRICANT SHEAR STRENGTH (M pa) Stearic acid 1.32 Calcium stearate 1.47 Magnesium stearate 1.96 Boric acid 7.16 graphite 7.35 04/21/16 Sagar KiShor Savale
Force volume relationship. 2727 FIG. Decreasing porosity with increasing compressional force for single ended pressing i) initial repacking ii) Elastic deformation iii) Plastic deformation iv) compression End of compressional process is when bulk volume = tapped volume. porosity (E)= 0  Decrease in porosity is due to two process: 1. Filling of large spaces by Interparticulate Slippage. 2. Filling of small voids by deformation or fragmentation at high loads.  A more complex sequence of events during compression process involves four stage as shown in fig., 04/21/16 Sagar KiShor Savale
Heckel plot. • It follows 1st order The pore in the mass are the reactant. log 1/E = KyP + Kr E = porosity P = Applied pressure Ky= material dependent constant Ky inversely proportional to it’s yield strength (S) (Ky = 1/3S) Kr = related to repacking stage & hence E0 For cylindrical tablet, P = 4F / ∏×D2 here, P = applied pressure D = tablet diameter F = applied compressional force 282804/21/16 Sagar KiShor Savale
2929 E = 100×[1 – 4w/ρt ×∏×D2×H] here, w = weight of tabletting mass. ρt = true density. H = thickness of tablet. •Type a : Soft material(e.g., NaCl) • Type b: Hard material(e.g., lactose) • Crushing strength of tablet is directly proportional to Ky. APPLICATION OF HECKEL PLOT: •Used to check lubricant efficacy. • For interpretation of consolidation mechanisms. •Duberg & nystom distinguish between plastic and elastic deformation characteristics of a material. 04/21/16 Sagar KiShor Savale
Kawakita Equation. C = Vi – Vp/ Vt = abPa / 1+ bPa C = degree of volume reduction, Vi = initial apparent volume, Vp =powder volume under applied pressure Pa, Vt = true volume, a & b = constants.  LIMITATION: Compaction process can be described upto certain pressure, above which the equation is no longer linear. 303004/21/16 Sagar KiShor Savale
Cooper and Eaton Equation. Vi – Vp/ Vi– Vt = C2 exp (-K2/Pa ) + C3 exp (-K3/Pa) C2,C3, K2,K3 = constants.  LIMITATION : Applies only to single component analysis. 313104/21/16 Sagar KiShor Savale
Energy expenditure. 323204/21/16 Sagar KiShor Savale
Crushing strength. Compression force applied diametrically to tablet. Measured by- o Monsanto tester. o Pfizer tester. o Erweka tester. o Schleuniger tester. o Strongcobb tester. Fracture across granule – size of granule influence strength 3333 Fig:- pfizer tester. 04/21/16 Sagar KiShor Savale
Friability. 3434 • Measures the resistance for abrasion. Parameter indicating tablet weight loss. F = 100 x (1 – wo/w) 0.8% -1.0% upper limit for acceptance . Fig:- Roche friabilater 04/21/16 Sagar KiShor Savale
Lamination and Capping. Laminating- Separation of tablet into two or more distinct layer. Capping – Partial or complete separation of top and bottom crowns of tablet from the main body. 353504/21/16 Sagar KiShor Savale
3636 REASONS FOR CAPPING AND LAMINATING. 04/21/16 Sagar KiShor Savale
Minimizing capping and lamination.  use of flat punch.  use of tungsten carbide insert.  proper set up of press.  addition .  use of binders. 373704/21/16 Sagar KiShor Savale
References:-  Keith marshall 1987,Compression and consolidation of powderd solids, Leon lachman, Herbert a.Liberman, & Joseph kanig ,The theory and practice of industrial pharmacy, third edition varghese publication house,bombay, pp.66,68,70-88.  Eugene parrott , 2007,Compression,Herbert A.Liberman, Leon Lachman & Joseph B.Schwartz ,Pharmaceutical dosage forms, tablets, volume ii,pp.201-241.  Stanforth J.N,Aulton’s pharmaceutics the design and manufacturing of medicine,third edition,Churchill livingstone elsevier,pp.176,177.  Subrahmanyam C.V. ,Micromeritics, Textbook Of Physical Pharmaceutics, Second Edition,vallabh prakashan,delhi,Pp-180-234.  Gilbert S. Banker , Christopher T. Rhodes, Modern Pharmaceutics , Fourth Edition.Pp.408-409.  encyclopedia of pharmaceutical Technology, Second Edition,volume- 3.Pp.303-305 383804/21/16 Sagar KiShor Savale
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