Page 717 - Carrahers_Polymer_Chemistry,_Eighth_Edition

680 Carraher’s Polymer Chemistry

12. They decompose slowly in water.
13. Often undefined with combinations of structures.

o
14. Evidently below 145 C.
15. As heat stabilizers for PVC processing and a variety of uses to inhibit unwanted
microorganisms.
16. The presence of a vacant low-lying p orbital.
17. Because of the potential properties that are not readily available in more traditional polymers.
18. Readily available starting materials, wide use temperatures, and variability in properties from
more traditional polymers.
19. Chlorophyll and hemoglobin. There are others.
20. Directional bonding that is present in bonds with some degree of covalent character.

CHAPTER 12
1. Held together by directional covalent bonds; acts physically like many organic polymers that
are above their T ; very viscous, acts as a solid on rapid impact but as a liquid on a much elon-
g
gated time scale.
2. Readily available on a large scale; inexpensive; relatively nontoxic; stands up well to most nat-
ural elements such as rain, cold, heat, mild acids and bases, and light; strong.
3. Fiberglass, colored glass, concrete, and so on.
4. Polymers where the structure cannot be adequately described on the basis of a single fl at plane.
Diamond, Portland cement, sand, topez, beryl, and so on. (see Table 10.1). Insoluble; many

exhibit long-range disorder; difficult to characterize structurally.
5. Wide variety of applications and conditions of application with some materials more appropri-
ate than others for specifi c applications.
6. Flows like a liquid, but the flow rate is very low.

7. Four main methods are employed for shaping glass. They are drawing, pressing, casting, and

blowing. Drawing is employed for shaping flat glass, glass tubing, and for creating fi brous glass.
Most flat glass is shaped by drawing a sheet of molten glass (heated so it can be shaped but not

so much that it freely flows) onto a tank of molten tin. Since the glass literally floats on the tin,
it is called “fl oat glass.”
8. Wide variety of applications that require materials that may possess glass-like properties—
good resistance to natural elements, easily shaped, polished, and cut, many transmit light and
can be colored.
9. Fiberglass and asbestos; fibers generally impart greater strength and fl exibility.

10. Quartz—highly crystalline.
11. When pressure is applied to a slice of quartz, it develops a net positive charge on one side of the
quartz slice and a negative charge on the other side. This phenomenon is the piezoelectric gen-
eration of a voltage difference across the two sides of the quartz crystal. Also, the same effect
is found when pressure is applied not mechanically, but through application of an alternating

electrical field with only certain frequencies allowed to pass through the crystal.
12. Most of what we do and use have risks involved: taking a sun bath and getting skin cancer;
taking a water bath and slipping on the soap; walking across a street and being run over; and
so on. Some risks may be necessary but others are not. We have many additives in our foods
that prevent spoilage, but if certain additives are found to be cancer causing we should omit

the use of those additives and find safe substitutes. We have found that the widespread use

of asbestos as insulation is unacceptable and are currently using fiberglass as an appropriate
alternative.
13. Anisotropic means that properties vary with direction. Since graphite is a sheet material, prop-
erties such as strength vary depending on whether you measure the strength along the fl at sheet
(it is relatively high) or between the sheets (it is relatively weak).

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