Chemistry Reference
In-Depth Information
and filled materials, the clarity and color purity of thermoset polymers is usually of
less importance than that of linear, thermoplastic materials. For this reason also,
lower purity monomers and side reactions during polymerization can sometimes be
tolerated to a greater extent when thermosetting polymers are being manufactured.
An example of
such side reactions occurs during the attempted self-
polymerization of
-hydroxyacids like lactic acid (7-1), which dehydrates readily
at temperatures near 250
C.
α
H
CH
3
C
COOH
OH
7-1
It is also possible to produce low-molecular-weight cyclic compounds in pref-
erence to linear polymers. An example is provided by the homologous series of
amino acids, H
2
N
(
CH
2
)
x
a
COOH
[3]
.
a
a
H
CH
2
N
(7-9)
2 H
2
N
CH
2
COOH
O = C
C = O + 2H
2
O + No polymer
N
H
CH
2
H
(7-10)
H
2
NCH
2
CH
2
COOH
NH
3
+ CH
2
C
COOH + No polymer
CH
2
H
2
N
CH
2
COOH
CH
2
C = O + H
2
O + No polymer
(7-11)
3
NH
CH
2
CH
2
C = O + H
2
O + No polymer
H
2
N
CH
2
COOH
CH
2
CH
2
4
(7-12)
NH
CH
2
CH
2
CH
2
C = O
n H
2
N
CH
2
COOH
NH +
N
CH
2
C
y
5
5
n - y
CH
2
CH
2
O
CH
2
~25%
~75%
(7-13)
