Rheology Chapter 19 Quiz
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Questions and Answers

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?

    <p>Quasisolids</p> Signup and view all the answers

    What happens as the degree of dilatancy increases?

    <p>N decreases</p> Signup and view all the answers

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

    <p>Pseudoplastic systems</p> Signup and view all the answers

    What is thixotropy defined as?

    <p>A slow recovery of consistency through shearing</p> Signup and view all the answers

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

    <p>They are highly dependent on the rate of shear</p> Signup and view all the answers

    What does the thixotropic coefficient, M, represent?

    <p>The loss in shearing stress per unit increase in shear rate</p> Signup and view all the answers

    What does negative thixotropy or antithixotropy refer to?

    <p>An increase in viscosity with increased time of shear</p> Signup and view all the answers

    How does negative thixotropy differ from dilatancy?

    <p>Negative thixotropy involves low solids content, while dilatancy involves high solids content</p> Signup and view all the answers

    How is the thixotropic coefficient, M, calculated?

    <p>$M = \frac{v2 \ln (v2)}{v1 \ln (v1)}$</p> Signup and view all the answers

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

    <p>Colloidal solutions</p> Signup and view all the answers

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

    <p>It has a yield value</p> Signup and view all the answers

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

    <p>Mobility</p> Signup and view all the answers

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

    <p>$U = 𝐹− 𝑓𝐺$</p> Signup and view all the answers

    What is the hysteresis loop used to measure?

    <p>Degree of thixotropy</p> Signup and view all the answers

    How is the thixotropic coefficient, B, calculated?

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

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

    <p>Degree of thixotropy</p> Signup and view all the answers

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

    <p>Assessing the degree of thixotropy</p> Signup and view all the answers

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

    <p>The system becomes more viscous and less elastic</p> Signup and view all the answers

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

    <p>The down curve is identical to the up curve</p> Signup and view all the answers

    What does thixotropy refer to in rheology?

    <p>The fast recovery of consistency after shearing</p> Signup and view all the answers

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

    <p>They are highly dependent on the rate at which shear is increased or decreased</p> Signup and view all the answers

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

    <p>To measure the area between the up curve and down curve of a rheogram</p> Signup and view all the answers

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

    <p>The rate of breakdown with time at constant shear rate</p> Signup and view all the answers

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

    <p>The breakdown of a plastic system when subjected to increasing shear rates</p> Signup and view all the answers

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

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

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

    <p>It indicates the force of flocculation in the suspension</p> Signup and view all the answers

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

    <p>Pseudoplastic flow exhibits no yield value, while plastic flow does</p> Signup and view all the answers

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

    <p>Pseudoplastic material has a constant viscosity, while plastic systems' viscosity varies with shear rate</p> Signup and view all the answers

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

    <p>The rheograms exhibit non-linear behavior with varying rates of shear</p> Signup and view all the answers

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

    <p>It can influence the selection of processing equipment</p> Signup and view all the answers

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

    <p>Heterogeneous dispersions can be described by a single value of absolute viscosity</p> Signup and view all the answers

    What does the term 'rheology' specifically refer to?

    <p>The science of flow and deformation of solids and liquids</p> Signup and view all the answers

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

    <p>It involves both viscous properties of liquids and elastic properties of solids</p> Signup and view all the answers

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