Fision

tacticity Arrangement of the pendant groups in space; i.e., isotactic, syndotactic, atactic.
van der Waals forces Secondary forces based on the attraction between groups.
viscosity Measure of theresistance of a polymer or polymer solution to flow.
EXERCISES
(To answer some of these questions you may need to look at other parts in the book for structures
and specific details.)
1. Makesketches or diagrams showing (a) a linear polymer, (b) a polymer with pendant groups,
(c) a polymer with short branches, (d) a polymer with long branches, and cross-linked polymers
with (e) low and (f )high cross-linked density.
2. Which has (a) the greater volume for the same weight of material and (b) the lower softening point:
HDPE or LDPE?
3. What is the approximate bond length of the carbonatoms in (a) a linear and (b) a cross-linked
polymer?
4. What is the approximate contour length of an HDPE chain with an average DP (chain length) of
n ¼ 2000 and of a PVC chain of the same numberof repeating units?
5. Which of the following are monodisperse polymers with respect to chain length? (a) hevea rubber,
(b) corn starch, (c) cellulose from cotton, (d) an enzyme, (e) HDPE, (f) PVC,(g) a specific DNA,
(h) nylon 6,6, or (i) a specific RNA?
6. What is the average DP of LDPE having an average molecular weight of 28,000?
7. What is the structure of the repeating unit in (a) PP,(b) PVC, and (c) hevea rubber?
8. Which of the following is a branched chain polymer: (a) HDPE, (b) iPP, (c) LDPE, or (d) amylose
starch?
9. Which of the following is a thermoplastic: (a) ebonite,(b) Bakelite, (c) vulcanized rubber, (d) HDPE,
(e) celluloid, (f) PVC, or (g) LDPE?
10. Which has the higher cross-linked density: (a) ebonite or (b) soft vulcanized rubber?
11. Do HDPE and LDPEdiffer in (a) configuration and (b) conformation?
12. Which is a trans isomer: (a) gutta percha or (b) hevea rubber?
13. Which will have the higher softening point: (a) gutta percha or (b) hevea...