Podcast
Questions and Answers
What does the term 'Rheology' specifically refer to?
What does the term 'Rheology' specifically refer to?
Who was the first to introduce the concept of Rheology?
Who was the first to introduce the concept of Rheology?
How is 'shear viscosity' denoted in the equations relating shear stress and shear rate?
How is 'shear viscosity' denoted in the equations relating shear stress and shear rate?
What unit does viscosity have in the SI unit system?
What unit does viscosity have in the SI unit system?
Signup and view all the answers
According to Newton's principles on fluid flow, how is the flow of liquids compared?
According to Newton's principles on fluid flow, how is the flow of liquids compared?
Signup and view all the answers
What defines a Newtonian fluid?
What defines a Newtonian fluid?
Signup and view all the answers
Which statement is true regarding the viscosity of Newtonian fluids?
Which statement is true regarding the viscosity of Newtonian fluids?
Signup and view all the answers
What happens to the shear stress in a Newtonian fluid when the shearing process is interrupted?
What happens to the shear stress in a Newtonian fluid when the shearing process is interrupted?
Signup and view all the answers
Which property is NOT associated with Newtonian fluids?
Which property is NOT associated with Newtonian fluids?
Signup and view all the answers
What characterizes a pseudoplastic fluid?
What characterizes a pseudoplastic fluid?
Signup and view all the answers
Study Notes
Surface and Colloid Chemistry Rheology
- Rheology is the study of flow
- It's a Greek word, combining "rheo" (flow) and "logia" (study)
- It examines how substances deform and flow, especially those exhibiting time-dependent responses to stress
- Introduced by Professor Eugene Cook Bingham
- Bingham plastic fluid is named after him
- Based on principles of elasticity (Hooke, 1678) and viscosity (Newton, 1687)
- Fluids are made of overlapping layers
- Flow of liquids is analogous to a stack of cards slipping over each other
- Shear stress is the force applied to a liquid area
- Shear rate is the speed gradient of liquid layers
- Shear stress (τ) and shear rate (γ) have a ratio, η (viscosity) in Newtonian fluids, τ = ηγ
- Viscosity is a measure of resistance to internal friction or flow
- Internal friction is caused by forces between molecules at interfaces
- SI unit is Pascal.sec (Pa.S), CGS unit is poise (P)
- 1 mPa.s = 1 cP
- Hooke's elasticity and Newton's viscosity laws are linear
- Viscoelasticity can make the linearity of the relationship between shear stress and shear rate change over time
Newtonian Fluids
- Constant ratio between shear stress (τ) and shear rate (γ), η (viscosity)
- η = τ / γ
- Viscosity doesn't change with shear rate
- Tension in the simple shear flow is zero where the two normal tensions differences are zero
- Viscosity is constant during shearing
- Viscosity returns to zero when shearing stops
- Viscosity values at different deformations are proportional
Non-Newtonian Fluids
- Deviate from Newtonian flow behavior
- Linear relationship between shear stress and shear rate is impaired
- Examples include: colloidal solutions, emulsions, ointments, clay dispersions
Flow Types
-
Dilatant Flow: Viscosity increases with increasing shear rate or time
- Literature terms: "condensed flow" or "shear thickening flow"
- Examples: cornstarch, vinyl resin pastes, sand-water mixtures, 50% solid content suspensions
-
Pseudoplastic Flow: Viscosity decreases with increasing shear rate
- Also called "shear thinning"
- Examples: Paints, emulsions, polymeric solutions. This is the most common type of non-Newtonian flow
-
Bingham Plastic Flow: Exhibits solid-like behavior under stable conditions
- Requires a specific yield stress for flow to start
- Examples: Flocculated suspensions (1-10% solid content), mayonnaise, ointments, toothpaste, ketchup
Additional information
- Summary/lab compensations will be covered in the upcoming week.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
This quiz covers the fundamentals of rheology, the study of flow in substances, focusing on key concepts such as shear stress, shear rate, and viscosity. It also highlights the contributions of notable figures like Professor Eugene Cook Bingham. Test your understanding of how materials deform and flow under stress.
