Rheology Chapter 19 Quiz

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Which class of materials exhibit both viscous properties of liquids and elastic properties of solids?

Polymers
Metals
Ceramics
Viscoelastic materials (correct)

In pharmacy, which of the following systems belong to the viscoelastic class?

Injectable solutions
Creams, lotions, and suspensions (correct)
Nasal sprays and eye drops
Tablets and capsules

Which pharmaceutical area is rheology significant for the physical stability of disperse systems?

Solids
Fluids (correct)
Quasisolids
Processing

For which pharmaceutical area is rheology significant in the capacity of solids to mix with miscible liquids?

Quasisolids (D) Signup and view all the answers

What happens as the degree of dilatancy increases?

N decreases (D) Signup and view all the answers

What type of systems show a displacement of the downcurve to the left of the upcurve in rheograms?

Pseudoplastic systems (B) Signup and view all the answers

What is thixotropy defined as?

A slow recovery of consistency through shearing (B) Signup and view all the answers

What is the relationship between rheograms obtained with thixotropic materials and the rate of shear?

They are highly dependent on the rate of shear (C) Signup and view all the answers

What does the thixotropic coefficient, M, represent?

The loss in shearing stress per unit increase in shear rate (C) Signup and view all the answers

What does negative thixotropy or antithixotropy refer to?

An increase in viscosity with increased time of shear (C) Signup and view all the answers

How does negative thixotropy differ from dilatancy?

Negative thixotropy involves low solids content, while dilatancy involves high solids content (B) Signup and view all the answers

How is the thixotropic coefficient, M, calculated?

$M = \frac{v2 \ln (v2)}{v1 \ln (v1)}$ (D) Signup and view all the answers

What type of materials exhibit plastic flow according to the text?

Colloidal solutions (C) Signup and view all the answers

What is the property of a Bingham body that distinguishes it from other materials in terms of flow?

It has a yield value (D) Signup and view all the answers

What property is analogous to fluidity in Newtonian systems for non-Newtonian materials?

Mobility (D) Signup and view all the answers

What equation describes plastic flow, as mentioned in the text?

$U = 𝐹− 𝑓𝐺$ (C) Signup and view all the answers

What is the hysteresis loop used to measure?

Degree of thixotropy (D) Signup and view all the answers

How is the thixotropic coefficient, B, calculated?

$\frac{U_1-U_2}{\ln(t_2/t_1)}$ (A) Signup and view all the answers

What does the area between the up curve and down curve of a rheogram represent?

Degree of thixotropy (B) Signup and view all the answers

What is the significance of determining the structural breakdown of a plastic system possessing thixotropy?

Assessing the degree of thixotropy (B) Signup and view all the answers

What happens to the system as the degree of dilatancy increases?

The system becomes more viscous and less elastic (D) Signup and view all the answers

What behavior is observed in Newtonian systems when the rate of shear is reduced after reaching the maximum?

The down curve is identical to the up curve (C) Signup and view all the answers

What does thixotropy refer to in rheology?

The fast recovery of consistency after shearing (A) Signup and view all the answers

How are rheograms obtained with thixotropic materials affected by the rate of shear?

They are highly dependent on the rate at which shear is increased or decreased (B) Signup and view all the answers

What is the primary purpose of using a planimeter or other suitable technique in rheology?

To measure the area between the up curve and down curve of a rheogram (B) Signup and view all the answers

What is the thixotropic coefficient, B, used to calculate?

The rate of breakdown with time at constant shear rate (A) Signup and view all the answers

In rheology, what does the term 'structural breakdown' refer to?

The breakdown of a plastic system when subjected to increasing shear rates (B) Signup and view all the answers

How is the thixotropic coefficient, M, calculated in relation to the plastic viscosities of the two downcurves?

$\frac{U_1 - U_2}{ln(t_2/t_1)}$ (A) Signup and view all the answers

What is the significance of the yield value in a plastic system?

It indicates the force of flocculation in the suspension (C) Signup and view all the answers

What distinguishes pseudoplastic flow from plastic flow in terms of rheology?

Pseudoplastic flow exhibits no yield value, while plastic flow does (D) Signup and view all the answers

How is the viscosity of a pseudoplastic material different from that of a plastic system?

Pseudoplastic material has a constant viscosity, while plastic systems' viscosity varies with shear rate (B) Signup and view all the answers

What can be inferred about the relationship between rheograms obtained with thixotropic materials and the rate of shear?

The rheograms exhibit non-linear behavior with varying rates of shear (C) Signup and view all the answers

What is the practical significance of analyzing the rheologic properties of pharmaceutical products?

It can influence the selection of processing equipment (D) Signup and view all the answers

How are simple liquids different from heterogeneous dispersions in terms of rheologic properties?

Heterogeneous dispersions can be described by a single value of absolute viscosity (D) Signup and view all the answers

What does the term 'rheology' specifically refer to?

The science of flow and deformation of solids and liquids (A) Signup and view all the answers

In rheology, what is the significance of the term 'viscoelasticity'?

It involves both viscous properties of liquids and elastic properties of solids (A) Signup and view all the answers