Compaction Properties: Hygroscopicity, Powder Rheology
Compaction Properties: Hygroscopicity, Powder Rheology
Compaction Properties: Hygroscopicity, Powder Rheology
(1) HYGROSCOPICITY:-
CONTENTS :-
A. INTRODUCTION
B. METHOD OF DETERMINATION
C. IMPORTANCE OF MEASUREMENT
D. METHOD OF IMPROVEMENT
(A) INTRODUCTION :
Hygroscopicity: - It is the tendency of material to absorb moisture from atmosphere &
get dynamic equilibrium with water in the atmosphere.
Deliquescent: - It is the hygroscopic substance which absorb moisture from air and they
can be liquefied by partially or wholly forming solution.
PHARMAQUEST
CLASSIFICATION OF SUBSTANCES :-
Essentially After 1 Week
CLASS
Below Moisture Above Moisture
%RH content (%) %RH content (%)
(III)-Moderately 60 LT 5% 80 LT 50%
hygroscopic
(IV)-Very hygroscopic 40-50 Higher 90 MT 30%
PHARMAQUEST
New smart excipient:
Galen IQ, a range of multifunctional excipient by German company palatlinit
• It is based on hydrogenated isomaltulose,also known as isomalt
• Combined advantage of mannitol, sorbitol, lactose, MCC
• Low Hygroscopicity, at 25˚C temperature hardly absorb water untill 85% RH.
• This low hygroscopic nature combined with anti caking property makes easy mixing,
agglomeration or tableting and helps in elimination of costly packing.
CONTENTS:-
A. INTRODUCTION
B. IMPORTANCE OF FLOW PROPERTY STUDIES
C. FACTOR INFLUENCING FLOW PROPERTY
D. IMPROVEMENT OF POWDER FLOW PROPERTY
E. MEASUREMENT OF FLOW PROPERTY
(A) INTRODUCTION
The flow properties of powder plays an important role in dosage form manufacturing
process.
When limited amounts of drugs are available these can be evaluated simply by
measurement of bulk density and angle of repose.
These are extremely useful derived parameters to assess the impact of changes in drug
powder properties as new batches become available.
PHARMAQUEST
4.Electrostatic effects
5.Powder cohesion and storage compaction
6.Effect of temperature
3. MOISTURE :
The effect of moisture on flowability of particles varies from powder to powder.
The particles become cohesive due to moisture absorption.
Absorbed moisture in solids can exist in two forms :
1. unbound state
2. As a part of crystal structure
4. ELECTROSTATIC EFFECTS :
The charged material show poorer flow than uncharged material.
Particles acquire static charge by :
Grinding
Attrition
collision
mixing
sieving
Moisture
Electro static charge may be positive or negative.
+ve charge particles plastic surfaces
-ve charge particles metal or glass surfaces
PHARMAQUEST
5. POWDER COHESION & STORAGE COMPACTION :
When solid remains at rest or stored in a hopper or bin , it can become more
cohesive and gives poor flow.
Flow chacteristics depends on :
Intrinsic cohesiveness of the material
Temperature of storage
Load levels of Hopper and bin
Time of storage
Vibratory forces
1. Bulk density :-
Bulk density of a compound varies substantially with the method of crystallization,
milling, or formulation.
PHARMAQUEST
It is determined by pouring presieved (40-mesh) bulk drug into a graduated cylinder via-
a large funnel and measuring the volume and weight.
2. Tapped density :-
It is determined by placing a graduated cylinder containing an known mass of drug or
formulation on a mechanical tapper apparatus, which is operated for a fixed numbers of
taps(about-1000)untill the powder bed volume has reached a minimum volume. using
the weight of a drug in the cylinder and this minimum volume,the tapped density is
calculated.
3.Carr’s Index:-
Neumann and carr developed a simple test to evaluate flowability of a powder by
comparing the poured (fluff)density and tapped density of a powder and the rate at
which it packed down.
Tapped Density - Bulk Density
% Compressibility = X 100
(Carr’s index) Tapped Density
4. HAUSNER RATIO:-
Hausner predict the flow properties of powder by using interparticle friction.
This is a simple index that can be determined on small quantities of powder.
Hausner ratio = tapped density /poured density
PHARMAQUEST
Typical values of Bulk Density,Tapped Density, Hausner Ratio & Carr’s index :-
Lactose -product Bulk density Tapped Hausner ratio Carr’s index
Lactochem- Domo density
5. Angle Of Repose :-
Angle of repose is defined as the angle of the free surface of a pile or heap of
powder to the horizontal plane.
Characterize the flow properties of solids.
If material is not cohesive If material is cohesive
PHARMAQUEST
REPOSOGRAPH :
• It is a stable instrument which at best can only indicate comparative flow properties.
• The formation of sharp cone would mean poor flow property
while a good spread would indicate a superior flow property.
Relationship between angle of repose, carr’s index of a powder and its flow characteristics:-
When only small quantities of powder are available, an alternative is to determine the
‘angle of spatula’ by picking up a quantity of powder on a spatula and estimating the
angle of the triangular section of the powder heap viewed from the end of the
spatula.this is obviously crude but is useful during preformulation,when only small
quantities of drug are available.
METHODS OF DETERMINATION :-
PHARMAQUEST
6. SHEAR CELL DETERMINATIONS :-
Characterize the flowability from the behavior of powder in a shear cell
The powder bed was subjected to shear and its applied load for shear also noted
Graph plotted between shear stress and applied load
Flow factor can be obtained by determining the reciprocal of slope.
FLOW FACTOR TYPE OF FLOW
> 10 Free flow
4 – 10 Easy flow
1.6 - 4 Cohesive
(3)COMPACTION PROPERTIES:-
CONTENTS:-
A. DEFINITION
B. DIFFERENT STAGES OF POWDER COMPACTION
C. METHOD FOR IMPROVEMENT
D. EFFECT OF COMPACTION ON DIFFERENT FACTORS
E. MOISTURE AND COMPRESSION
F. EVALUATION OF COMPACTION
A. DEFINITION:-
COMPACTION :- Compaction of powder is term used to describe the situation in which
material are subjected to some level of mechanical force.
COMPRESSION :- Compression is reduction in the bulk volume of the material as a result of
displacement of the gaseous phase.
PHARMAQUEST
CONSOLIDATION :- Consolidation is an increase in mechanical strength of material
resulting form particle – particle interactions
PHARMAQUEST
non hygroscopic, non carcinogenic, chemically stable, suitable for diabetics.
high compressibility, high binding capacity, low friability.
excellent diluent, binder, ideal for chewable tablet.
PHARMAQUEST
F. EVALUTION OF COMPACTION:-
1. Strain index (SI) :- Measures internal strain associated with a powder when compacted.
2. Bonding index (BI) :-Ability of material to bonds.
3. Brittle fracture index (BFI) :- Measures brittleness of material.
Higher is the BI index, stronger is the tablet.
Higher is the SI index, softer is the tablet.
REFERENCES :-
Michael .E. Aulton, Pharmaceutics- the science of dosage form design,135 ,207,second
edition,Elsevier Limited.
Leon Lachman et al, Theory and Practice of Industrial Pharmacy, 184-186, Third edition,
Varghese publishing house, India.
www.quantachrome.com
Stephen. A.howard, Flow properties of solids, “ Encyclopedia of pharmaceutical
technology” by markel dekker,2nd edition, volume-2, page no-1264 -1283
N.K. Jain, Flow ,cohesiveness and compressibility, “Professional pharmacy” by vaallabh
prakashan, 5th edition,1998 pg no-145-147
Harry G. Brittain, Physico chemical properties, ,”Physical characterization of
pharmaceutical solids” by markel dekker.inc,1995 pg.no-281-301
CHEMICAL ABSTRACT: VOL: 151,No.7,17th AUGUST, 2009, P.NO.-156034
CHEMICAL ABSTRACT : VOL :146, Jan. 2007, P.NO.: 9806
CHEMICAL ABSTRACT : VOL:151,No.6,10th AUGUST, 2009,P.NO.-131556
PHARMAQUEST