Chemistry Reference
In-Depth Information
Table 6.11
(continued)
Polymer
T
g
(
C)
T
m
(
C)
References
References
34-40
[
177
]
180
[
177
]
n
60-65
[
177
]
240
[
177
]
n
10
[
177
]
162-168
[
177
]
n
a
From refs. [
196
-
198
]
6.13 Copolymers of Styrene
Many copolymers of styrene are manufactured on a large commercial scale. Because styrene
copolymerizes readily with many other monomers, it is possible to obtain a wide distribution of
properties. Random copolymers form quite readily by free-radical mechanism [
185
,
194
]. Some can
also be formed by ionic mechanism. In addition, graft and block copolymers of styrene are also
among commercially important materials.
Most comonomers differ from styrene in polarity and reactivity. A desired copolymer composition
can be achieved, however, through utilization of copolymerization parameters based on kinetic data
and on quantum-chemical considerations. This is done industrially in preparations of styrene-acry-
lonitrile, styrene-methyl methacrylate, and styrene-maleic anhydride copolymers of different
compositions.
6.13.1 High-Impact Polystyrene
For many applications, the homopolymer of styrene is too brittle. To overcome that, many different
approaches were originally tried. These included use of high molecular weight polymers, use of
plasticizers, fillers (glass fiber, wood flour, etc.), deliberate orientation of the polymeric chains,
copolymerization and addition of rubbery substances. Effect of plasticizers is too severe for practical
use, and use of high molecular weight polymers exhibits only marginal improvement. Use of fillers,
