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Copyright Cengage Learning. Powered by Cognero.
Page 1
1. Huge macromolecules are formed by the ____ of small mers.
a.
pyrolysis
b.
polymerization
c.
hydrolysis
d.
oxidation
ANSWER:
b
2. The type of polymerization that begins at one location by the action of a chemical initiator and almost instantaneously
completes the chain without yielding chemical byproducts is called ____ polymerization.
a.
condensation
b.
catalytic
c.
emulsion
d.
chain growth
ANSWER:
d
3. When monomers combine to form blocks two units long and then, in turn, combine to form blocks four units long, in
sequence, it is known as ____ polymerization.
a.
stepwise
b.
emulsion
c.
chain growth
d.
catalytic
ANSWER:
a
4. Chain polymerization and stepwise polymerization produce molecules of varying molecular lengths, resulting in the
need to ascertain the number and weight ____ of the distribution.
a.
polydispersity index
b.
standard deviation
c.
average molecular weight
d.
physical properties
ANSWER:
c
5. Because determining average molecular lengths of a sample is difficult, manufacturing companies use ____ for a
“quick and dirty” estimation of the average molecular lengths in a sample.
a.
polydispersity index
b.
melt index values
c.
mode values
d.
the median value
ANSWER:
b
6. The selection of a grade of material is complicated so petrochemical companies provide ____values on material data
sheets (MSDS).
a.
average molecular weight
b.
polydispersity index
c.
MFI
d.
standard deviation
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Chapter 08: Characterization and Selection of Commercial Plastics
Copyright Cengage Learning. Powered by Cognero.
Page 2
ANSWER:
c
7. To avoid using solvents, emulsion and suspension polymerization processes utilize ____to surround the tiny droplet of
monomer.
a.
melting agents
b.
condensers
c.
catalysts
d.
water
ANSWER:
d
8. In bulk polymerization, ____ guarantee a high ratio between surface area and volume.
a.
narrow, tubular reactors
b.
catalysts
c.
small drops of monomer
d.
heat stabilizers
ANSWER:
a
9. In polymerizing polystyrene from styrene monomers, the monomer is dissolved in about 80 percent ____.
a.
water
b.
formaldehyde
c.
benzene
d.
acetaldehyde
ANSWER:
c
10. A common byproduct of stepwise polymerization is ____and hydrogen chloride.
a.
formaldehyde
b.
acetaldehyde
c.
benzene
d.
acetic acid
ANSWER:
d
11. The polydispersity index (PI) is similar to a ____ for normal distribution
a.
mean
b.
standard deviation
c.
mode
d.
median
ANSWER:
b
12. Commercial polymers range from a PI of about 2 to____.
a.
10
b.
20
c.
30
d.
40
ANSWER:
d
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Page 3
13. When a melt flow index (MFI) increases, the flow length ____.
a.
drops to zero
b.
decreases
c.
increases
d.
is unaffected
ANSWER:
c
14. Changes in the MFI are ____ average chain lengths (the average molecular weight).
a.
independent of
b.
inconsistently related to
c.
positively correlated with
d.
inversely correlated with
ANSWER:
d
15. In selecting material grade plastics, high-flow grades often include internal ____ to promote flow.
a.
lubricants
b.
metals
c.
carbonaceous materials
d.
glass additives
ANSWER:
a
