Chemistry Reference
In-Depth Information
O
+
CH
2
OOH
O
2
O
2
O
OO
O
O
+
O
Further oxidative degradation of fragments leads to formation of a carboxylic acid, an ester, and a
g
-lactone [
522
]. It was also found that the main oxidation products of polyethylene are an acid and a
ketone. On the other hand, polypropylene yields upon oxidation approximately equal quantities of an
acid, a ketone, an aldehyde, an ester, and a
-lactone [
522
].
In order for a polymer molecule to be attacked by oxygen, it must come in contact with it. This
means that oxygen must be able to permeate into the material. Otherwise, all the oxidation will occur
only at the surface. It was shown that oxidation occurs more readily in amorphous regions of the
polymers where permeation of oxygen is not hindered by the chains being packed tightly together in
the crystallites. That is only true, of course, at temperatures below
g
T
m
of the polymer.
polystyrene
was investigated thoroughly. It was
found that the rate of oxygen absorption and the number of chain scissions remain constant up to a
high degree of reaction. There is no evidence of cross-linking under these circumstances [
523
].
During the degradation process, carbonyl groups accumulate in the polymer [
524
]. Among the
degradation products were identified benzaldehyde [
525
] and a number of ketones [
526
].
The primary oxidation and chain scission process in polystyrene at room temperature is as
follows [
527
]:
Among the chain-growth polymer, oxidation of
OO
O
HOO
O
+
the reaction can also proceed in this manner:
