Rheological Properties of Pharmaceuticals Flashcards
Starch is __ as its viscosity increases with increase in shear stress
dilatant
Bingham plastics follow Newton’s law of viscosity at low shears. T/F?
F. below yield value, behave as elastic solid; above yield value,behave as newtonian system
Select which physical property is NOT rheological property
a) body and slip
b) spreadability
c) surface tension
d) viscosity
c) surface tension
Rheology can be defined as
study of flow properties
unit of kinematic viscosity is defined as
stoke
Plastic flow is generally exhibited by
a) gellies
b) lotion
c) colloids
d) conc solid suspensions
d) conc solid suspensions
Pseudoplastic flow is generally exhibited by
a) viscous pastes
b) sol of mucilages and gums
c) gellies
d) lotion
b) sol of mucilages(viscous secretion) and gums
unit of relative viscosity is
dimensionless
creep test is applied to evaluate the viscoelastic properties of what kind of formulation?
ointments
deflocculated suspension with high conc of the dispersed solids exhibits the flow of type
a) dilatant
b) newtonian
c) plastic
d) pseudoplastic
a) dilatant
unit of viscosity is defined as
poise
In graph of shear stress(F) vs shear rate(G), what would happen if shearing is stopped?
stress in fluids fall immediately to 0(origin) when stop shearing
A graph of viscosity vs shear rate, why the graph is horizontal?
- viscosity is independent of shear rate
2. viscosity is constant with time
diff btw kinematic viscosity and dynamic viscosity?
kinematic concerns with time taken to pour out, dynamic concerns with force used to make it flow
Examples of non-newtonian fluid
plastic, pseudoplastic, dilatant
What is dilatant flow?
opposite to pseudoplastic; viscosity increase with increase in shear rate
To produce a stable suspension of solid particles,
Select one or more:
an electrolyte should be added.
a thickening agent should be added.
the concentration of dispersed phase must be very low.
the size of solid particles must be reduced.
a ththe size of solid particles must be reduced.ickening agent should be added.
An oil-in-water emulsion
Select one or more:
contains particles of similar size.
is stabilised by surfactant adsorption on the surface of particles.
is stabilised by electrical repulsion between particles.
will show faster phase separation if viscosity is reduced.
is stabilised by surfactant adsorption on the surface of particles.
is stabilised by electrical repulsion between particles.
will show faster phase separation if viscosity is reduced.
When solid particles in an aqueous medium are flocculated,
Select one:
the particles settle faster to the bottom.
viscosity decreases.
zeta potential increases.
shape of particle changes.
the particles settle faster to the bottom.
According to the DLVO theory, irreversible particle aggregation can occur as a result of the thermal energy of the particles overcoming the following energy barrier:
Select one:
Primary maximum.
Secondary minimum.
Primary minimum.
Secondary maximum.
Primary maximum.
