Page 221 - Carrahers_Polymer_Chemistry,_Eighth_Edition

184 Carraher’s Polymer Chemistry

25. What is the relationship between R and R under steady-state conditions?
i t
26. What is the relationship between average DP and R and R ?
p t
27. Draw a structure of what iPP looks like.
28. What percentage of polymer is usually found when a polymer produced by chain-reaction poly-
merization is heated above its ceiling temperature?
29. What is the relationship between the average degree of polymerization and initiator concentra-
tion in cationic chain polymerization.
30. Can the polymers found in the bottom of a bottle of insolubilized formaldehyde solution be
useful?
31. How would you prepare stable polymers from formaldehyde?
32. Why is the thermal decomposition of polymers of formaldehyde called unzipping?
33. Discuss advantages of the soluble stereoregulating catalysts in comparison to the Natta-Zeigler
catalysts.
34. Why are there so many widely used PEs.

35. How would you increase the flow rate of water in a fi re hose?
36. Why is poly-3,3-bischloromethyloxybutylene crystalline?
37. Why are PP and PE the most widely used polymers?
38. What kind of polymers are made from lactones?
39. How could you remove unsaturated hydrocarbons from petroleum or coal tar distillates?
40. What species is produced by the reaction of an anionic chain polymerization initiator and the
monomer?
41. What are the propagation species in anionic chain polymerizations?
42. Why are polymers produced by the anionic polymerization of pure monomers called “living
polymers?”
43. Using the symbols A and B for repeating units in the polymer chain, which of the following is a
block copolymer: (a) ABAABABBABAAB, (b) ABABABABAB, or (c) AAAAAABBBBBB?
44. What is the most widely used monadic nylon?
45. What is the repeating unit for nylon-4?
46. What is the catalyst and cocatalyst in the most widely used Ziegler-Natta catalyst?
47. Name two structures that are possible from the polymerization of 1,3-butadiene.
48. What is the principle difference between propagation reactions with butyllithium and a Ziegler-
Natta catalyst?
49. What are some physical properties that iPP would have in comparison to aPP.
50. Show the skeletal structures of cis- and trans-polyisoprene.
51. Write formulas for repeating units in the chains of (a) poly-1,4-isoprene and (b) poly-1,2-
isoprene.
52. What is the most widely used catalyst for the production of HDPE?
53. What elastomer is produced by anionic chain polymerization?
54. What elastomer is produced by use of a Ziegler-Natta catalyst?

55. What are difficulties associated with the use of solid-state catalysts in the production of
polymers?
56. How are the diffi culties associated with the use of solid-state catalysts overcome by the use of
soluble stereoregulating catalysts.
57. What are some considerations in determining which PE is used to produce bags for a lawn and
garden store?

58. How might you produce a polymer with good flexibility from crystalline HDPE that is strong
but does not have the desired fl exibility?
59. One table lists the ultimate elongation of a material as 60% and another lists the supposedly
same general material with an ultimate elongation of 6,000. How can you account for this large
difference?

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