Page 718 - Carrahers_Polymer_Chemistry,_Eighth_Edition

Solutions 681

14. Quartz and graphite are both made from carbon and both are highly ordered in structure. Quartz
has tetrahedral carbons while graphite has trigonal planer carbons, which are layered one upon
the other, and so on.
15. It may be related to such factors as abundance and the ability of both silicon and carbon to form
a large variety of structures. It is also probably related to the ability of carbon to connect with
itself and for silicon to react with oxygen that, in turn, react with other Si-O containing units
forming the silicates.
16. Relatively to the alternative materials employed to manufacture optical lenses, glass holds up
better to high temperatures; it is also clear, transparent, and resistant to abrasion and scratching
and is easily cleaned. It is superior in its resistance to the elements and to common chemicals.
17. Supposedly, the individual plates of the old glass windows found in Europe are a little thicker
at the bottom than at the top.
18. Readily available in large quantities, inexpensive, and they possess the properties that allow
them to perform needed applications.
19. Most organic dyes decompose at relatively high temperatures necessary to incorporate the col-
oring material into the glass.
20. In truth, it depends on the particular ceramic and who is doing the evaluation. Many ceramics
contain polymeric sheets, cluster, and/or chains that are connected to one another through ionic
linkages, thus they are hybrids between ionic compounds and polymers.
21. The structure is varied; the material is not soluble; there are lots of “kinds” or “types” of
Portland cement; structure varies with amounts of materials added and with age. It does not
have a precise structure but only an average structure.
22. Both require very pure silicon dioxide.

23. Probably not because of the number of better alternatives and it is difficult to live down its
negative past history. Further, there is no reason to believe that the somewhat brittle asbestos
compositions might not eventually break down into sizes that would negatively affect the lungs.
Also, the problem with asbestos is not only its size but also its sharpness. It would be reasonable
to believe that the new asbestos might also be sharp creating health problems when ingested.
24. Carbon nanotubes are being used/studied as tips in atomic force microscopy, electrical wires
and switches, manufacture of super slick materials, and so on.
25. It might be but it probably is not sufficiently free from impurities to give a good clear fi nal

product. Beach sand also is composed of minor amounts of other materials that do not behave
as sand. In any case, beach sand is generally a mixture of a variety of silicon-intense materials
and not a good source of “glass-making” silicon dioxide.

CHAPTER 13

1. Because many polymers, often being poor conductors, are so widely used in electrical
applications.
2. (a).
3. Because they are poor conductors of heat.
4. ATF.
5. Almost every organic compound will burn if the conditions are good for combustion. Tests such
as the oxygen index are useful as comparative tests only.
6. (a).
7. The nature of the surface is important to many of the overall properties of materials.
8. It is particularly important when two or more materials are placed together because their ther-
mal expansions need to be similar or they may break apart.
9. NMR tools can be used to determine structural units, but at times assist in describing interac-
tions between chains and within chains such as chain folding.
10. About 190–800 μm.

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