Chemistry Reference
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Composition and properties of radicals, being formed under the light action, depend on
conditions of experiment (temperature, light intensity, spectral composition of light and
soon). Besides, EPR spectra of some radicals depend on cellulose structure. That is why EPR
spectra of cellulose have complex character. Problem of these spectra interpretation has not
been completed yet, and identification of a number of radicals is debatable. Analysis and
conclusions, made while discussing investigations on cellulose photodestruction, greatly
facilitate the approach to similar processes understanding, taking place at light-ageing of di-
and triacetate of cellulose, though they have their own features [153, 154].
The process of cellulose acetate oxidation under the action of light energy proceeds
according to chain mechanism with formation of free radicals and different gaseous products
[155, 156, 157]. Depending on conditions of irradiation proportion of rates of separate stages
of chain process changes, but unfortunately, kinetic parameters of this process are not defined
and this does not allow to judge the length of the chain of cellulose acetate (CA)
photooxidation.
Investigation of the mechanism of photo- and photooxidative destruction has shown [141,
154 158] that intrinsic viscosity decreases at photodestruction of cellulose acetate, content of
combined acetic acid also decreases and accumulation of carbonyl groups takes place. There
have been identified six main volatile products: CH 2 =C=O; CO; CO 2 ; H 2 ; H 2 O; CH 3 COOH,
moreover acetic acid is the main product [159]. In some authors opinion, break of acetal bond
1-4 and opening of pyranose cycle according to C 1 -C 2 happen at photodestruction of cellulose
acetate.
It has been stated that the first stage of chain process, developing at light action on
cellulose acetate, is appearing of free radicals [2]. Phototransformation of radicals, being
formed, has been discussed in details in works [2, 148. Probably, breaks of bonds may take
place according to the following mechanism:
Besides, the possibility that acetoxyl radical CH 3 COO* may be formed at trans-splitting
of acetal groups from cellulose acetate is not ruled out:
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