Rheology Flashcards
The study of deformation and flow properties of matter
rheology
(main components)
- resistance to flow
- property of liquids
viscosity
(main components)
- stickiness or structure
- property of solids
elasticity
newtonian systems
-shearing stress (F)
-rate of shear (G)
-fluidity
-kinematic viscosity
force per unit area required to bring about a flow
Shearing Stress (F)
Directly proportional to shearing stress
Rate of Shear (G)
Coefficient of viscosity or VISCOSITY
η →Greek letter “eta” [ey-tuh]
unit of viscosity
𝑔 / 𝑐𝑚 𝑠𝑒𝑐 𝑜𝑟 Poise (poiz)
centipoise (cp)
0.01 poise
Reciprocal of viscosity
- fluidity
- φ →Greek letter “phi” [fahy]
- φ = 𝟏 / 𝜼
absolute viscosity divided by density of the liquid at specific temperature,
- 𝝂 = 𝜼 / 𝝆
- ν →Greek letter “nu” [nyoo]
kinematic viscosity
unit of measurement for kinematic viscosity
stokes (s) or centistokes (cs)
(temperature dependence of viscosity) for liquids: when temperature increases
viscosity decreases
why do liquids and their viscosity act accordingly when it comes to their temperature?
due to decrease in intramolecular forces of attraction
(temperature dependence of viscosity) for gases: when temperature increases
viscosity increases
Examples are simple liquids, either pure chemicals or solutions, water
newtonian fluids
viscosity of newtonian fluids is ________ on the rate of shear
independent
Majority of fluid pharmaceutical products do not follow Newton’s law of flow.
non-newtonian systems
non-newtonian systems are generally exhibited by:
- colloids
- emulsions
- suspensions
- ointments
a non-newtonian fluid ________ when under stress or strain
changed its behavior
(determination of rheologic properties)
- Capillary Viscometer
- Falling Sphere Viscometer
newtonian liquids
(determination of rheologic properties)
- Rotational Viscometer
(1) Cup and Bob Viscometer
(2) Cone and Plate Viscometer
non-newtonian liquids
The viscosity of a Newtonian liquid can be determined by measuring the time required for the liquid to pass between two marks as it flows by gravity through a vertical capillary tube.
capillary viscometer
another name for capillary viscometer
ostwald viscometer
A glass or steel ball rolls down an almost vertical glass tube containing the test liquid at a known constant temperature. The rate at which a ball of a particular density and diameter falls is an inverse function of the viscosity of the sample.
falling sphere viscometer
another name for falling sphere viscometer
hoeppler viscometer
the sample is sheared in the space between the outer wall of a bob and the inner wall of a cup into which the bob fits.
cup-and-bob viscometer
rotating cup
couette type - macmichael viscometer
rotating bob
searle type - brookfield and stoermer viscometer
- the sample is placed at the center of the plate, which is then raised into position under the cone.
- A variable-speed motor drives the cone, and the sample is sheared in the narrow gap between the stationary plate and the rotating cone.
CONE-AND-PLATE VISCOMETER
another name for cone-and-plate viscometer
ferranti-shirley viscometer
Exhibit both viscous fluidity and elastic solidity when undergoing deformation
viscoelasticity
