Page 541 - Carrahers_Polymer_Chemistry,_Eighth_Edition

504 Carraher’s Polymer Chemistry

EXERCISES

1. What is the difference between morphology and rheology?
2. Which of the following is/are viscoelastic: (a) steel, (b) polystyrene, (c) diamond, or
(d) neoprene?

3. Define G in Hooke’s law.

4. Which would be isotropic: (a) a nylon filament, (b) an extruded pipe, or (c) ebonite?
5. What are the major types of stress tests?
6. Describe in molecular terms what a dashpot represents.
7. Which will have the higher relaxation time: (a) unvulcanized rubber or (b) ebonite?
8. Describe in molecular terms what a spring represents.

9. Define what compliance is.
10. What does viscoelastic mean?
11. Below the glass transition temperature a material should behave in what manner?
12. At what temperature would the properties of polystyrene resemble those of hevea rubber at
35 K above its T ?
g
13. Define Young’s modulus. Should it be high or low for a fi ber?

14. Define the proportionality constant in Newton’s law.

15. What term is used to describe the decrease of stress at constant length with time?
16. In which element or model for a viscoelastic body, (a) Maxwell or (b) Voigt–Kelvin, will the
elastic response be retarded by viscous resistance?
17. What is the most important standards organization in the Unites States?
18. For most polymeric materials, is failure abrupt or continuous?
19. Is it safe to predict long-range properties from short time period results for plastics?
20. Describe the importance of relating models to stress–strain results.
21. If a sample of polypropylene measuring 5 cm elongates to 12 cm, what is the percentage of
elongation?
2
22. If the tensile strength is 705 kg/cm and the elongation is 0.026 cm, what is the tensile
modulus?
23. Defi ne creep.

24. Briefly describe a Voigt–Kelvin model.
25. What changes occur in a polymer under stress before the yield point?
26. What changes occur in a stress polymer after the yield point?
27. How can you estimate relative toughness of polymer samples from stress–strain curves?
28. What effect will a decrease in testing temperature have on tensile strength?
29. What effect will an increase in the time of testing have on tensile strength?
30. Describe a Maxwell model.

ADDITIONAL READING

Alfrey, T. (1948): Mechanical Behavior of High Polymers, Interscience, NY.
Boyd, R., Smith, G. (2007): Relaxations in Polymers, Cambridge University, NY.
Bicerano, J. (2002): Prediction of Polymer Properties, 3 Ed., Dekker, NY.
rd
Brinson, H., Brinson, L. (2007): Polymer Engineering Science and Viscoelasticity: An Introduction, Springer,
NY.
Brostow, W., D’Souza, N., Menesses, V., Hess, M. (2000): Polymer Characterization, Wiley, NY.
Darinskii, A. A. (2006): Molecular Mobility and Order in Polymer Systems, Wiley, Hoboken.
Dealy, J. M., Larson, R. G. (2006): Molecular Structure and Rheology of Molten Polymers, Hanser-Gardner,
Cincinnati, OH.
Greenhalgh, E., Hiley, M., Meeks, C. (2009): Failure Analysis and Fractography of Polymer Compositions,
CRC, Boca Raton, FL.
nd
Gupta, R. K. (2000): Polymer and Composite Rheology, 2 Ed., Dekker, NY.

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