This document discusses rheological properties of emulsions. It explains that emulsions often exhibit non-Newtonian flow, making their rheological properties complex. The factors that influence emulsion rheology include properties of the dispersed phase like volume fraction, particle size, and viscosity, properties of the continuous phase like viscosity, and the type and concentration of emulsifying agent used. Understanding how formulation impacts rheology allows pharmacists to develop emulsions with appropriate flow properties for their intended uses and manufacturing processes.

1. UNIT-III
Coarse Dispersion
EMULSIONS
Presented by
Dr. A. SUMATHI
Professor & Head
Department of Pharmaceutics
FOURTH
SEMESTER
B.PHARM
PHYSICAL
PHARMACEUTICS-II

2. Emulsions
2
● Theories of emulsification
● Stability of emulsions
● Preservation of emulsions
● Rheological properties of emulsions
● Emulsion formulation by HLB method
● Microemulsion and multiple emulsions
Dr. A. SUMATHI
EMULSIONS

3. Rheological
Properties of
Emulsions
3

4. Rheological Properties of Emulsions
4
Emulsified products
During preparation or use
Undergo a variety of shear stresses
● Flow properties of the product will be vital for proper performance of
the emulsion under the conditions of usage or preparation
- Eg. Spreadability of dermatologic or cosmetic products
Dr. A. SUMATHI
EMULSIONS

5. Rheological Properties of Emulsions
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● Importance of Flow Characteristics
 Flow of parenteral emulsion through hypodermic needle
 Removal of emulsion from a bottle or tube
 Various milling operations employed in large scale manufacturing
of emulsions
Dr. A. SUMATHI
EMULSIONS

6. Rheological Properties of Emulsions
6
● Role of Pharmacist
 To appreciate how formulation can influence the rheological
properties of emulsions
● Most emulsion exhibits Non- Newtonian Flow
(Except Dilute ones) complicates
Data interpretation & Quantitative comparison
between different formulations
Dr. A. SUMATHI
EMULSIONS

7. Rheological Properties of Emulsions
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According to SHERMAN, the factors that influence the flow properties of
Emulsion are the viscosity related properties of
● Dispersed phase
● Continuous phase
● Emulsifying agent
Dr. A. SUMATHI
EMULSIONS

8. Dispersed phase
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● Phase Volume Ratio
● Particle size distribution
● Viscosity
Dr. A. SUMATHI
EMULSIONS

9. Phase Volume Ratio
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When the volume concentration of dispersed phase is
 LOW (<0.05) Newtonian System
 Increased the system becomes more resistant to flow
Exhibits
Pseudoplastic flow characteristics
 At sufficiently high concentration Plastic flow occurs
 Approaches 0.74 Inversion may occur Marked change in viscosity
Dr. A. SUMATHI
EMULSIONS

10. Particle size distribution & Viscosity
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● Reduction in mean particle size increases the viscosity
● Wider the particle size distribution, the lower the viscosity
- When compared to a system having a similar mean particle size but a
narrower particle size distribution
Dr. A. SUMATHI
EMULSIONS

11. Continuous phase
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● Viscosity
 The effect of the viscosity of the continuous phase may be greater
than that predicted by determining the bulk viscosity of the
continuous phase alone
 Viscosity of a thin liquid film (100 to 200 A) is several times the
viscosity of the bulk liquid
Dr. A. SUMATHI
EMULSIONS

12. Continuous phase
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● Higher viscosities exist in concentrated emulsions when the thickness of
the continuous phase between adjacent droplets approaches these
dimensions
● Sherman points about the reduction in viscosity with increasing shear
● It may be due in part to decrease in viscosity of continuous phase as the
distance of separation between globules is increased
Dr. A. SUMATHI
EMULSIONS

13. Emulsifying Agent
13
Type of emulgent
affect
Particle flocculation &
Interparticle attractions
In turn modify
Flow properties
Dr. A. SUMATHI
EMULSIONS
Greater the concentration
of emulgent
Higher will be the viscosity
of the product
Other significant factors
Physical & Electrical
properties of the film

14. THANK YOU
Dr. A. SUMATHI
Professor & Head
Department of Pharmaceutics