Chemistry Reference
In-Depth Information
In oxidations of hydrocarbons, oxygen is believed to act as a diradical in the ground state. This
would explain radical combination reactions:
R
þ
O
O
!
R
O
O
and the subsequent hydrogen abstraction reaction:
R
0
H !
R
0
R
O
O
þ
RO
OH
þ
The rate of formation of the peroxy radical is much higher than is the rate of hydrogen abstraction
[
521
]. The overall rate of oxidation of polymeric materials by atmospheric oxygen is strongly
affected by light, heat, oxygen concentration, moisture, and the presence of traces of impurities.
The impurities, however, can act as either catalysts or as inhibitors of oxidation.
The degradation of
was studied on poly(isopropylidine carboxylate) [
518
] over a
range of temperatures, from 200 to 800
C. Among the decomposition products were found
tetramethyl glacolide, acetone carbon monoxide, and to a lesser extent methacrylic acid. The primary
decomposition product appears to be tetramethylene glacolide that becomes an intermediate upon
further pyrolysis:
poly-a-esters
O
Δ
O
O
O
O
O
O
O
O
O
O
O
O
O
+
O
O
O
also:
O
O
Δ
O
O
+
CO
+
was studied on poly[2,2
0
-propane-bis-(4-phenyl) carbonate]
[
519
]. It was concluded that a rearrangement mechanism is the main intermediate material in
subsequent formation of carbon dioxide and volatile phenolic compounds [
519
]:
Decomposition of polycarbonates
O
OH
O
Δ
OO
O
O
+
H
2
O
O
