Study Set Content:
Curve begins at the origin
Pseudoplastic
No yield value
Pseudoplastic
Reverse effect to pseudoplastic flow
Dilatant
Viscosity increases with increasing rate of shear
Dilatant
Viscosity decreases with increasing shear rate
Pseudoplastic
Suspensions containing a high concentration (about 50% or
greater)
Dilatant
Ex. Starch in water, zinc oxide
Dilatant
Ex. Polymer solution, Na alginate, Pentylcellulose, PEG
Pseudoplastic
(gel-sol transformation) fluid after agitation but resume their
solid state after being undisturbed for a period of time.
Thixotropy
have the advantage that the
particles remain in more or less permanent suspension during
storage and yet when required for use, the paste are readily
made fluid by tapping or shaking.
Thixotropic preparations
Most apparent characteristic of a thixotropic system is the
hysteresis loop (up and down curves of the rheogram)
Measure of thixotropic breakdown obtained by planimeter or
suitable technique.
Area of Hysteresis
Represents an increase rather than a decrease in
consistency on the down-curve (sol-gel formation).
Negative Thixotropy/Antithixotropy
Are deflocculated and ordinarily contain greater than 50% by
volume of solid dispersed phase
Dilatant systems
Have low solid content (1% -10%) and are flocculated.
Antithixotropy systems
A rare phenomenon in which the longer the fluid undergoes
shearing forces, the higher the viscosity.
Rheopexy
Gel is the equilibrium form
Rheopectic system
Sol is the equilibrium form
Antithixotropic system
The property of materials wherein this exhibit both the
viscous properties of liquids as well as the elastic property
of solids.
The property of materials wherein this exhibit both the
viscous properties of liquids as well as the elastic property
of solids.
When materials are subjected to stress for a period of time, they
undergo slight deformation under the influence of the stress but
once the stress is removed, they exhibit their behavior by returning
to their original shape with little permanent deformation.
Viscoelasticity
