Page 712 - Carrahers_Polymer_Chemistry,_Eighth_Edition

Solutions 675

42. The structure of PTFE is regular. The large pendant group in FEP destroys this regularity.
43. Both the average DP and R are proportional to N/2, where N/2 is the number of active
p
micelles.
44. (b). The additional chlorine on the repeating unit increases the specifi c gravity.
45. Probably because they cost less and often are easier to synthesize.
46. Would still probably go by a chain-type mechanism but the reaction would be much faster at a
given temperature so would probably be carried out at lower temperatures.
47. Probably for a number of reasons, including the great potential for use and profit. In both cases,

it is good to understand the system so that you can optimize it and tailor it as needed.

48. An engineering plastic is a plastic that can be cut, sawed, drilled, and so on. Teflon can be cut,
sawed, and drilled, but it often undergoes distortion when these operations occur so it is often
called a “near” engineering plastic.

49. A plastisol is made by heating finely divided PVC with a plasticizer.
50. A comonomer that can accept dye molecules is added to the polymer.
51. PMMA scratches more easily; about as clear; higher impact strength; less environmentally sta-
ble; less resistant to solvents; lighter (less dense).
52. In live animal tests, generally with mice, some plasticizers have shown negative health effects.
While the amounts and reactions in humans may not be the same, these results signal a concern
that care should be taken and further examination of the use of these specific plasticizers be

monitored.

CHAPTER 7
1. Let S = styrene and A = acrylonitrile units.
(a) –(–S–)– and –(A–)–;
(b) –SASASASASA–; (c) –AASASSASAAASSASSASASSSASAA–;
(d) −AAAAAAAASSSSSSSSSAAAAAAAASSSSS−;
(e) −SSSSSSSSSSSSSS−
− −
A n A n
2. Equimolar.
3. r = k /k and r = k /k .
12
11
21
22
2
1
4. No, they are constant.
5. They vary in accordance with the Arrhenius equation.
6. Vinylidene chloride, about 76%; vinyl chloride about 24%.
7. Styrene and so on.
8. (a) cationic, (b) anionic or free radical, and (c) Ziegler–Natta.
9. Alternating.
10. (M ) (M ) (M )
1 n
2 m
1 n
11. r r = 1
1 2
12. (b).
13. Most elastomeric material is cross-linked and thus are thermoset and not easily processable.
14. (a) 50% of each, (b) 91% S and 9% MMA, and (c) 94% MMA and 6% S.
15. Isobutylene, 71%; isoprene, 29.6%.
16. Isobutylene, 96%.
17. Add a mixture of monomers to maintain the original ratio of reactants.
18. B can also form crystalline segments themselves.
19. Vinyl chloride, 68%.
20. The presence of vinyl acetate mers in the chain breaks up the regularity characteristic of PVC
so that the copolymer has a lower T , is more soluble in organic solvents, more fl exible, and is
g
more readily processed.

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