In this slide contains introduction, copmpression, consolidation, compaction, heckel plots and equation, interpretation and application. Presented by: NARAYAN SINGH UDIT (Department of pharmaceutics). RIPER, anantapur

1. 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

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
Contents
Introduction
 Compression
 Consolidation
 Compaction
Compaction Equations
Heckel Plot & Equation
Types of materials
Interpretation
Applications of Heckel plot
Limitations of Heckel plot
2

3. 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

4. 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

5. 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

6. 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

7. RIPER
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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

8. RIPER
AUTONOMOUS
NAAC &
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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.

9. RIPER
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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

10. RIPER
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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.

11. RIPER
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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

12. RIPER
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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))

13. RIPER
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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))

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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))

15. 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

16. RIPER
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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

17. 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

18. 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

19. RIPER
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NAAC &
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Raghavendra Institute of Pharmaceutical Education and Research - Autonomous
K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 19
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