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Heckel Plots for Tablet Compression

The document presents a seminar on Heckel plots for tablet compression as part of the M.Pharm curriculum at Raghavendra Institute of Pharmaceutical Education and Research. It covers concepts such as compression, consolidation, compaction, and the Heckel equation, detailing the methods used to analyze powder densification under pressure. The seminar discusses different types of materials, their behavior during compression, applications of Heckel plots, and potential limitations affecting their use.

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Raghavendra Institute of Pharmaceutical Education and Research - Autonomous K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 Heckel Plots for Tablet Compression A Seminar as a part of curricular requirement for I year M.Pharm I semester Raghavendra Institute of Pharmaceutical Education and Research(RIPER)- Autonomous JNT University Anantapur Master of Pharmacy in Pharmaceutics Presented by UDIT NARAYAN SINGH (20L81S307) Under the guidance of Dr. C H Pavan Kumar Head of the Department Department of Pharmaceutics
RIPER AUTONOMOUS NAAC & NBA (UG) SIRO- DSIR Raghavendra Institute of Pharmaceutical Education and Research - Autonomous K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 Contents Introduction  Compression  Consolidation  Compaction Compaction Equations Heckel Plot & Equation Types of materials Interpretation Applications of Heckel plot Limitations of Heckel plot 2
RIPER AUTONOMOUS NAAC & NBA (UG) SIRO- DSIR Raghavendra Institute of Pharmaceutical Education and Research - Autonomous K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 Compression 3 Unit Particle Pressure Void Space Reduced Void Space Compressed Compression Reduction in bulk volume of a material By removal of gaseous phase (Void) By application of Force/ Pressure
RIPER AUTONOMOUS NAAC & NBA (UG) SIRO- DSIR Raghavendra Institute of Pharmaceutical Education and Research - Autonomous K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 Consolidation 4 Unit Particle Pressure Void Space More Interaction More Strength Consolidation Increase in Mechanical strength of material Due to Particle-Particle Interaction and Unification By application of Force/ Pressure Less Interaction Less Strength
RIPER AUTONOMOUS NAAC & NBA (UG) SIRO- DSIR Raghavendra Institute of Pharmaceutical Education and Research - Autonomous K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 Compaction 5 Unit Particle Pressure Void Space More Dense Compacted Compaction (Compression + Consolidation) Increase in Density, Reduction in Volume By formation of bonds between particles as they move closer By application of Force/ Pressure Less Dense
RIPER AUTONOMOUS NAAC & NBA (UG) SIRO- DSIR Raghavendra Institute of Pharmaceutical Education and Research - Autonomous K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 6 A compaction equation relates some measure of the state of consolidation of a powder, such as porosity, volume (or relative volume), density, or void ratio, as a function of the compaction pressure. Compaction Equations Compaction Equation Kawakita Equation Heckel Equation Walker Equation
RIPER AUTONOMOUS NAAC & NBA (UG) SIRO- DSIR Raghavendra Institute of Pharmaceutical Education and Research - Autonomous K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 7 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, Where, D is relative density of tablet (tablet density/true powder density) P is the applied pressure K is the slope of the straight line portion of Heckel Plot A is the intercept. Heckel Equation ln (1/1-D) = KP + A
RIPER AUTONOMOUS NAAC & NBA (UG) SIRO- DSIR Raghavendra Institute of Pharmaceutical Education and Research - Autonomous K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 8 It is based upon analogous behavior to a first order reaction The Heckel analysis is a popular method of determining the volume reduction mechanism under the compression force Based on the assumption that powder compression follows first order kinetics with the interparticulate pores as the reactants and the densification of the powder as the product. Contd.
RIPER AUTONOMOUS NAAC & NBA (UG) SIRO- DSIR Raghavendra Institute of Pharmaceutical Education and Research - Autonomous K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 9 In 1961, Heckel postulated a linear relationship between the relative porosity (Inverse density) of a powder and the applied pressure Plotting the value of (1/(1-D)) against applied pressure, P, yields a linear graph having slope, K and intercept, A Reciprocal of K i.e., Heckel Constant, yields a material- dependent constant known as Yield Pressure. Heckel Plot
RIPER AUTONOMOUS NAAC & NBA (UG) SIRO- DSIR Raghavendra Institute of Pharmaceutical Education and Research - Autonomous K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 10 The slope of the linear regression is Heckel constant Large values of Heckel constant indicate susceptibility to plastic deformation at low pressures Yield Pressure is inversely related to the ability of the material to deform plastically under pressure Low values of yield pressure indicate a faster onset of plastic deformation Intercept of the line indicates degree of densification by rearrangement. Heckel plot allows for interpretation of the mechanism of bonding. Contd.
RIPER AUTONOMOUS NAAC & NBA (UG) SIRO- DSIR Raghavendra Institute of Pharmaceutical Education and Research - Autonomous K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 11 Type of Materials On basis of Heckel Plot Soft, Readily undergo plastic deformation Harder materials, Higher yield pressure, First brittle fracture then plastic flow Rearrangement stage is absent, Densification is due to plastic deformation Type A Type C Type B
RIPER AUTONOMOUS NAAC & NBA (UG) SIRO- DSIR Raghavendra Institute of Pharmaceutical Education and Research - Autonomous K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 12 A linear relationship is observed, with the plots remaining parallel as the applied pressure is increased Indicative that deformation is apparently only by plastic deformation They are comparatively soft and readily undergo plastic deformation They retain different degrees of porosity depending on the initial packing of the powder in the die. Example - Sodium Chloride. Type A Compression Pressure ln(1/(1-D))
RIPER AUTONOMOUS NAAC & NBA (UG) SIRO- DSIR Raghavendra Institute of Pharmaceutical Education and Research - Autonomous K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 13 There is a initial curved region followed by a straight line Indicates that the particles are fragmenting at the early stages of the compression process Brittle fracture precedes plastic flow Occur with harder materials with higher yield pressures Such materials undergo compression by fragmentation first, to provide a denser packing. Example – Lactose. Type B Compression Pressure ln(1/(1-D))
RIPER AUTONOMOUS NAAC & NBA (UG) SIRO- DSIR Raghavendra Institute of Pharmaceutical Education and Research - Autonomous K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 14 In such materials there is an initial steep linear region which become superimposed This superimposed region flattens out as the applied pressure is increased This behavior was ascribed due to the absence of a rearrangement stage Densification is due to plastic deformation and asperity melting. Example – Starch. Type C Compression Pressure ln(1/(1-D))
RIPER AUTONOMOUS NAAC & NBA (UG) SIRO- DSIR Raghavendra Institute of Pharmaceutical Education and Research - Autonomous K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 15 Type A Heckel plots usually exhibit a higher final slope than type B which implies that the former materials have a lower yield pressure This is because fragmentation with subsequent percolation of fragments is less efficient than void filling by plastic deformation In fact, as the porosity approaches zero, plastic deformation is the predominant mechanism for all materials Two regions of Heckel plot type B are thought to represent the initial repacking stage and subsequent deformation process The point of intersection corresponding to the lowest force at which a coherent tablet is formed. Interpretation
RIPER AUTONOMOUS NAAC & NBA (UG) SIRO- DSIR Raghavendra Institute of Pharmaceutical Education and Research - Autonomous K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 16 The crushing strength of tablets can be correlated with the values of K of Heckel plot – Larger K values indicate harder tablets Information from Heckel plot can be used as a means of binder selection while designing tablet formulations Heckel plot can be used to check lubricant efficacy Information from plot can be used to interpret consolidation mechanism. Heckel plots are also used to distinguish between substances that have different consolidation mechanism It can also be used as a means of assessing plasticity. Applications
RIPER AUTONOMOUS NAAC & NBA (UG) SIRO- DSIR Raghavendra Institute of Pharmaceutical Education and Research - Autonomous K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 17  Heckel plots can be influenced by – • Slight variation in true density • Variation in particle size • Overall time of compression • Degree of lubrication • Size of the die. Thus, the sensitivity of Heckel plots renders it useful as well as limits its application. As a slight variation affects the plot. Limitations
RIPER AUTONOMOUS NAAC & NBA (UG) SIRO- DSIR Raghavendra Institute of Pharmaceutical Education and Research - Autonomous K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 18 Shailendra M. Compression physics of pharmaceutical powders: A review. International Journal of Pharmaceutical Sciences and Research. 2012;6(3):1586.1587. Khar K R, Vyas S P, Ahmad J F, Jain K G. Lachman/Leiberman’s The Theory and Practice of Industrial Pharmacy. Delhi; India: CBS Publishers & Distributors; 2017. References
RIPER AUTONOMOUS NAAC & NBA (UG) SIRO- DSIR Raghavendra Institute of Pharmaceutical Education and Research - Autonomous K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 19 Thank You