Page 714 - Carrahers_Polymer_Chemistry,_Eighth_Edition

Solutions 677

15. Convenience, uniformity, speed, reproducibility, less exposure of workers to volatile monomers.
16. No. Before 1910, it was patented by Goodyear and used as a colorant. A compounder made a mis-
take and used a 100-fold excess and found that it was a good filler. Another accidental discovery.

17. You would expect that on the basis of size, O >N , that nitrogen would diffuse faster. Diffusion
2 2
can occur in both directions, into the tire and out of the tire. The tire can be considered as a
membrane where there is a drive for the concentration of components on both sides to be equal.
Since the concentration of nitrogen in air (78%) is greater than that of oxygen (21%), the driving
force for removal of nitrogen from the tire is less. Thus, use of certain nanocomposites such as
those that contain the silicates allow for the formation of a barrier that helps prevent movement
of gas into and out of the tire.
18. Nonsystematic testing is dangerous but since that is your task you might take several different

lengths of the new fiber and place them in some resins and note if they adhere to the resin and
to test their general strength. If there are promising results then further testing is called for.
Again, remember such unorganized testing may miss combinations that offer truly outstanding
performance.
19. Asbestos (health concerns), peanut shells, palm prongs (leaves), and corn husks.
20. In phase separation, the fiber material and resin material are not mixed together on a molecular

level, thus you do not get the reinforcing effect of having the strong fiber material dispersed
throughout the composite.

21. Since the fiber material in metal composites weights more, the density of these materials is gen-
erally greater than for regular organic composites.
22. Metal matrix composites, in comparison to polymer-intense composites, offer no moisture

absorption, greater fire resistance, higher use temperatures, greater radiation resistance, greater
stiffness and strength, and higher thermal and electrical conductivities.

CHAPTER 9
1. Enzymes are present in the human digestive system for the hydrolysis of the alpha linkages but
not for the beta linkages in polysaccharides such as cellulose and starch.
2. Cellobiose is a beta-glucoside, whereas maltose is an alpha-glucoside.
3. Because of the presence of intermolecular hydrogen bonds.
4. It is the same since there is an equilibrium between the alpha and beta conformations of the
d-glucose.
5. Cellulose mostly taken from wood pulp with the lignin removed.
6. Three.
7. Secondary cellulose acetate.
8. It forms an amine salt.
9. (a).
10. It is branched, therefore discourages the formation of hydrogen bonding.
11. 0.5.
12. Melanin
13. Increases.
14. Because of the formation of ordered regions.
15. An elastomer is an amorphous polymer with a low T and low intermolecular forces that
g
increases in entropy, order when stretched.
16. Guayule grows on arid soil in temperate areas and has a high content of natural rubber.
17. (b). Isoprene is the monomer in the synthetic process, and isopentenyl pyrophosphate is the pre-
cursor in natural rubber.
18. That NR is a member of the terpene family.
19. Because of the formation of crystals.
20. Change in entropy, −T(dS/dl).

9/14/2010 3:44:16 PM
K10478.indb 677 9/14/2010 3:44:16 PM
K10478.indb 677