Monday, February 3, 2014

Rheology, Viscosity, Shearing Stress, Dispersed System, Colloidal Dispersion, Colloids & Coarse Dispersion.



Rheology:
Rheology is the study of the flow and deformation properties of the matter.

Viscosity:
The viscosity of a fluid is its resistance to flow or movement.

According to flow, fluids are of two types. They are:-
1.       Newtonian Fluids &
2.       Non- Newtonian Fluids.

1.       Newtonian Fluids:- Liquids which follow Newton’s law of viscous flow are known as newtonian’s liquids.
2.       Non-Newtonian Fluids:- Liquids which do not follow Newton’s law are known as non-newtonian fluids.
Example: Colloidal dispersion, emulsions, suspensions and ointments.

Shearing Stress:
The force per unit area F/A required to bring about flow is called the “Shearing Stress”

·         The flow properties of Non-Newtonian Materials are three types. They are:-

1.       Plastic flow
2.       Pseudo plastic flow
3.       Dilatants flow.


Dispersed System:
A dispersed system is defined as a system in which one phase, the dispersed phase, is distributed uniformly as particles throughout another phase, called the sispersion medium or continuous phase.

Colloidal Dispersion:
If the particles have a size ranging from 1 nm to 1 µm, which is dispersed in the continuous phase, this system is called colloidal dispersion.

Colloids:
The particles have a size ranging from 1 nm to 1 µm is called colloids.

Because of their large surface area, colloids show greater efficiency for absorption or adsorption.
 
Coarse Dispersion:
The size of the dispersed particles ranging from 1 µm to 100 µm, which is dispersed in the continuous phase, this system is called coarse dispersion.

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