Powder Flow: the missing link in the evolution of powder characterization
Arjen P. Tinke
Janssen R&D
Department of Chemical Technology and Process Control (CTPC)
Turnhoutseweg 30
B‐2340 Beerse (BELGIUM)
Colloids
Suspensions = Solids + Liquids
Powders = Solids + Liquids + Gasses
A ‘suspension’ is not so much different than a ‘powder’
Is it?...
Particle‐particle interaction
•
•
•
•
Cohesion
Repulsion
Friction
Interlocking
Powder
Product variables that influence behaviour
• Size
• Shape
• Surface texture (roughness)
• Surface area
External variables that influence behaviour
• Consolidation
• Hygroscopicity
• Aeration
• Hardness / Friability
• Flow (shear) Rate
• Amorphous content
• Moisture
• Density
• Electrostatic Charge
• Cohesion
• Storage Time
• Adhesion
• Porosity
• Elasticity
• Potential for • Plasticity
electrostatic charge
Particle Size May Say It All
Particle size may have a large effect on bulk behaviour
•
•
•
•
•
•
Flowability / Rheology
Sedimentation rate
Abrasiveness
Explosion
Dissolution
etc.
Dissolution rate constant
Noyes‐Whitney equation
Particle size dependency
Laser Diffraction
Application area
• QC
• R&D
Added value
• Golden standard
• Black box
Sub Micron Sizing
Particle Characterization
Particle Size Distribution Imaging Bulk Characteristics
•
•
•
•
Laser Diffraction
Dynamic Light Scattering
(Automated) Static Image Analysis
Dynamic Image Analysis
• SEM
• Optical Microscopy
• Helium Pycnometry
• Gas Adsorption
Solid State Foreign Material Identification
Characteristics
• DSC
• XRD
• Dynamic Vapor Sorption
• Optical Particle Counting
• Dynamic Image Analysis
• IR and Raman Microscopy
Bench Top SEM
We’re Missing Something
A
B
d10 (m)
d50 (m)
d90 (m)
Batch A
1.8
5.7
11.4
Batch B
1.9
5.9
12.3
Fluid Imaging
Quality Aspects
Physical
Purity
Chemical
Purity
Powder
Characteristics
Drug
Substance
Powders in Pharm Industry
Spoutable
Sand‐like
Aeratable
Cohesive
Flow Obstruction
Milling chamber completely filled with powder
Obstruction of exit holes
Powder Technology
•
•
•
Particle Size
Morphology
Product Characteristics (e.g., flowability, mechanical properties)
Crystallization
Morphology
•
•
•
Solid‐Liquid Separation (incl. Drying)
Cohesion
Friction
Interlocking
Flowability
Brittleness
•
Non‐Intended Breakage
•
PAT
•
•
•
•
Milling
Mechanical Properties
Shear Impact
Intended Breakage
•
•
•
Tribo Electrification
(Static Charge)
Packaging & Transport
Particle Size Distribution
Up‐ and Down‐Scaling
Modelling
PAT
Conditioning
Structural Disorder
Relaxation
Surface Energy
Dynamic Image Analysis
Powder Characterization
Powder Flowability
• Bulk‐and‐Tap Density
• Static Angle‐of‐Repose • Dynamic AOR
Powder Rheology Particle Shape Distribution • Powder Rheology
• (Automated) Static Image Analysis –
Optical Microscopy
Surface Energy Surface Charge Mechanical Properties
/ Structure
• Inverse GC
• TAM
• Faraday cup
• Charge decay analysis
• Nano identation
• Micro hardness testing
Particle Shape
Static Image Analysis
For rectangular particles
the laser diffraction (LD)
particle size distribution
profile can be calculated
fairly well from the length and the width of the particles.
Powder Flowability
U.S. Pharmacopoeia
<267> Hg porosimetry
<429> Laser diffraction
<601> Inhalation
<616> Bulk and tapped density
<699> Helium pycnometry
<776> Optical microscopy
<786> Sieve testing
<811> Powder fineness
<846> Specific surface area
<1174> Powder flow
Funnel Static AOR BTD Dynamic AOR
Powder Rheology
Flow Behaviour
Excellent
Good
Fair
Passable
Poor
Very poor
Very, very poor
C
 10
11‐15
16‐20
21‐25
26‐31
32‐37
> 38
H
1.00‐1.11
1.12‐1.18
1.19‐1.25
1.26‐1.34
1.35‐1.45
1.46‐1.59
> 1.60
Scale of flowability
Data taken from USP <1174>
 (*)
(g.cm‐3)
1.30
Batch
Batch C
[o]
(g.cm‐3)
0.40
[n]
(g.cm‐3)
0.45
n½
H[n]
C[n]

16.0
1.12
10.3
14.1
Bulk-and-tap density data
(*)
[o]
[n]
n½
H[n]
C[n]

-
measured with helium pycnometry
bulk density (g.cm-3)
tap density (g.cm-3)
compaction kinetic factor
Hausner ratio (H[n]=[n]/ [o])
Compressibility factor, or Carr index (H[n]=100/(100-C[n])
characteristic relaxation time obtained from the fit of the experimental results
Classification of powder flowability after Jenike
Type of Flow
Free‐flowing
Easy‐flowing
Cohesive
Very cohesive and non‐flowing
FF
10 < FF 4 < FF < 10
2 < FF > 4
FF < 2
Cohesion
(kPa)
2.82
Batch
Batch C
UYS
(kPA)
11.2
Shear cell test results
UYS
MPS
FF
AIF
-
Unconfined Yield Strength
Major Principle Stress
Flow Function
Angle of Internal Friction
MPS
(kPA)
20.7
FF
1.85
AIF
(o)
36.4
Measurement Vessel
25 mm  10 mL
FT4 Powder Tester
Dynamic Flow
• BFE
‐ Basic Flowability Energy (mJ)
• SE
‐ Specific Energy (mJ/g)
• SI
‐ Stability Index
• FRI
‐ Flow Rate Index
• AE
‐ Aerated Energy (mJ)
• AR
‐ Aeration Ratio
• CE
‐ Consolidated Energy
Bulk
• CBD
• CPS
• PD
‐ Conditioned Bulk Density (g/mL)
‐ Compressibility Percentage (%)
‐ Pressure Drop across the Powder Bed
Shear
• C
• FF
• AIF
• WF
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‐
‐
‐
Cohesion (kPa)
Flow Function
Angle of Internal Friction (o)
Wall friction
Process
• Flow (Obstruction)
• Conveying
• Segregation
• Attrition
• Caking
• Electrostatics
• Moisture
• Agglomeration
• etc.
‘Powder Flow’
Fingerprint
Supportive Data
Conclusions
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PSD measurements work well in QC, but are not sufficient in R&D
•
‘Powder Flow’ is a broad area, which is more about ‘Flow Obstruction’ than about ‘Flow’
•
PHARMACOPOEIA
• Relevant for QC
• Less for R&D
• HOW
Characterization of ‘Powder Behaviour’
•
•
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Flowability testing
Powder rheology
Powder testing (FT4)
• WHY
Characterization of ‘Powder Characteristics’ •
•
•
•
Image analysis
Static charge
Surface energy
Etc.
Thank you for your attention!