Thixotropy Quiz & Flashcards in Pharmacy Applications

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What happens to the viscosity of thixotropic materials when shear stress is applied?

It becomes zero

It decreases suddenly (correct)

It increases suddenly

It remains constant

Why is thixotropy a desirable property in pharmaceutical applications?

For tablet formation

For injectable solutions

For immediate drug release

For sustained drug delivery system (correct)

What is the effect of temperature on the viscosity of liquids?

It remains constant

It becomes zero

It decreases (correct)

It increases

What is the effect of temperature on the viscosity of gases?

It increases Signup and view all the answers

What is the reason for the sudden increase of viscosity in dilatant fluids?

Formation of vacuum gaps between cluster of material particles Signup and view all the answers

What type of materials exhibit time-dependent reversible viscosities?

Thixotropic materials Signup and view all the answers

What is the significance of thixotropy in suspensions and emulsions?

It is desirable for sustained drug delivery system Signup and view all the answers

What is the term used to describe the force per unit area that causes a fluid to flow?

Shear stress Signup and view all the answers

What is an example of an intrinsic factor that affects viscosity?

Particle shape Signup and view all the answers

What is the term used to describe the amount of deformation caused by the shear stress?

Strain Signup and view all the answers

What is the relationship between stress and strain in a Newtonian fluid?

Linear Signup and view all the answers

What is the term used to describe the resistance of gases or fluids towards the flow due to shear stress?

Viscosity Signup and view all the answers

What is the inverse of viscosity?

Fluidity Signup and view all the answers

What is the term used to describe the study of the flow of liquids and the deformation of solids?

Rheology Signup and view all the answers

What is the significance of the slope of the line in the stress-strain relationship for non-Newtonian fluids?

It is a measure of the viscosity of the fluid Signup and view all the answers

Which type of non-Newtonian fluid exhibits a yield value, below which no flow occurs?

Plastic fluid Signup and view all the answers

What is the mechanism behind the behavior of pseudo-plastic fluids?

Rearrangement and orientation of polymer chains Signup and view all the answers

Which type of non-Newtonian fluid is also known as shear thickening fluid?

Dilatant fluid Signup and view all the answers

What is the characteristic of dilatant fluids?

Increase in viscosity with increasing shear stress Signup and view all the answers

What is the significance of the yield value in plastic fluids?

It is the minimum shear stress required for flow to occur Signup and view all the answers

What is the characteristic of pseudo-plastic fluids?

Decrease in viscosity with increasing shear stress Signup and view all the answers

What type of non-Newtonian fluids usually have a high solid content of more than 50%?

Dilatant fluids Signup and view all the answers

Study Notes

Introduction to Rheology

Rheology is the study of the flow of liquids and the deformation of solids, which affects the mixing and flow of materials, their packaging, and patient acceptability.
Rheology influences physical stability and biologic availability.

Flow and Viscosity

Flow occurs when stress is applied to a fluid, causing deformation.
Stress is the force per unit area, while strain is the amount of deformation caused by the stress.
Viscosity is the resistance of a fluid to flow due to shear stress, measured by the ratio of shear stress to shear rate.
Fluidity is the inverse of viscosity, representing the ease of flow.

Types of Fluids

Newtonian fluids have a linear relationship between stress and strain, with a constant viscosity at a given temperature.
Non-Newtonian fluids do not have a linear relationship between stress and strain, and their viscosity changes with the shear rate.

Non-Newtonian Fluids

Plastic fluids have a yield value, which is the minimum shear stress required to initiate flow.
Pseudo-plastic fluids, or shear-thinning fluids, have a high viscosity at rest but flow easily when shaken, with a changing viscosity and mobility along the curve.
Dilatant fluids, or shear-thickening fluids, have a high solid content and increase in viscosity with stress, often due to the formation of vacuum gaps between particles.

Thixotropy

Thixotropic materials have a time-dependent, reversible viscosity, decreasing with stress and returning to their original state when stress is removed.
This property is useful in pharmaceutical applications, such as sustained drug delivery systems, suspensions, and emulsions.

Factors Affecting Viscosity

Intrinsic factors: molecular size, particle shape, and intermolecular forces.
Extrinsic factors: temperature and additives.
Viscosity of liquids decreases with temperature, while viscosity of gases increases with temperature.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Learn about rheology, the study of the flow of liquids and deformation of solids, and its importance in pharmacy, including mixing, packaging, and patient acceptability.

Rheology in Pharmacy

Choose a study mode