Rheo – to flow Logos – science Ology – the study of Rheology is the science that concerned with “flow of fluid “ & “ deformation of solid”

2. Presentation on Rheology
Presented by-
1. Asraful Islam Rayhan
2.Md. Shafiul Islam
3.Md. Arman Ahmed
4.Md. Suhin Hossain
5. Mohammud Ali
Dept . Of pharmacy,
JESSORE UNIVERSITY OF SCIENCE & TECHNOLOGY.

3. What is rheology???

4. RHEOLOGY
Rheo – to flow
Logos – science
Ology – the study of
Rheology is the science that concerned with
“flow of fluid “ & “ deformation of solid”

5. Dr. Aldo Acevedo - ERC SOPS5
Rheological Properties
 Stress
 Shear stress
 Normal stress
 Normal Stress differences
 Viscosity
 Steady-state (i.e. shear)
 Extensional
 Complex
 Viscoelastic Modulus
 G’ – storage modulus
 G” – loss modulus
 Creep, Compliance, Decay
 Relaxation times

6. Manufacture of dosage forms.
Handling of drug for administration .
Acceptability & bioavailability are influence by the
rheological consideration of medicine.
Application of pharmaceutical & cosmetic products.
In preparation of ointment, syrup, suspension &
emulsion.
Importance of rheology

7. Viscosity

8.  Unit:-
*the fundamental unit of viscosity = poise
*C.G.S unit of viscosity = gm.𝑐𝑚−1
.𝑠−1
or dyne.s.𝑐𝑚−2
*S.I. unit of viscosity = Pa.S
Definition:- Viscosity may be defined as the
resistance to fl0w of liquid under stress. Flow
property of simple liquid is expressed in term of
viscosity.

9. Definition:-
kinematic viscosity is the absolute viscosity
which is defined as the viscosity divided by density of a
liquid at a specific temperature.
Kinematic viscosity , V =
𝑛
𝜌
Here,
n= viscosity
𝜌 = 𝑑𝑒𝑛𝑠𝑖𝑡𝑦
the unit of it is stoke (s) & contistoke (cs).
Kinematic viscosity

10. 1) In case of liquid:-
Viscosity of liquid is decreased with
increase temperature.
V∝
1
𝑇
2) In case of gas:-
Viscosity of a gas increase with the
increase of temperature.
V∝T
Effect of temperature on viscosity

12. There are basically two types of rheological
system, defined by the relationship between
shear stress and shear rate.
1) Newtonian
2)Non-Newtonian

13. The liquid have a viscosity that independent of shear
rate at constant temperature , known as newtonian
fluid.
A Newtonian fluid is a fluid or dispersion whose
rheological behaviour is described by Newton’s law of
viscosity.
Newtonian system

14. First Law:-
Every thing contains in it`s rest or uniform
motion in a straight line until it is acted upon by another
force.
Second Law:-
the rate of the change of momentum is
directly to the applied force & the direction of applied
force.
Third Law:-
there is an equal & opposite reaction.
Newton`s Law

15. Newtonian Rheogram

16. 1) Castor oil
2)Chloroform
3)Ethanol
4) Olive oil
5)Water
Examples of newtonian fluid

17. Non-Newtonian
Non-newtonian fluid is defined as the fluid for which the
relationship between shear stress & rate shear is not
constant.
Examples- 1) Emulsion
2)Suspension
3) Ointment

18. Types of Non-Newtonian
There are three types of Non-Newtonian-
1) plastic flow
2) Pseudo-plastic flow
3) Dilatant flow

19. Plastic flow:-
May be defined as the rheological phenomenon in
which the flowing behavior of the material occurs after
the applied stress reaches a critical value or yield value &
than behaves approximately as a newtonian flow.
The equation describing plastic flow as-
U= F-
𝒇
𝑮
where,
f=yield value
F=shear stress
G=Shear rate

20. Examples of substance that show plastic follow
1)Flocculated suspension
2) Ointment
3) Paste
4)Gel

21. Pseudoplastic or Shear-thinning :-
The reduction of viscosity with
increasing rate of shear in a steady shear flow.
Pseudoplastic flow Rheogram:-

22. 1) Tragacanath in water
2) Methyl cellulose in water
3) Toothpaste
Examples of Pseudoplastic

23. Dilatant flow or Shear-thickening:
The increase of viscosity
with increasing rate of shear in a steady shear flow.
E.g- cream

24. Thixotropy
An opposite case of this, is a fluid that thins out with
time and requires a decreasing stress to maintain a
constant strain rate.
Examples of thixotropic compound:-
1) Suspension ,emulsion
2) penicilline G IM injection

25. Viscoelasticity
Viscoelasticity may be defined as the property of
substance that exhibit both elastic & viscous behavior
when undergoes deformation in response to the
application of stress.
The substance that has viscoelasticity, is call viscoelastic
material.
e.g- polymeric liquid