J Polym Environ
Fig. 7 Identity of conformation
and arrangement of substituents
in cellulose acetate (top) and
naturally acetylated
polysaccharides like chitin
(middle) and acetylxylan (XA,
bottom)
materials in the environment. There are different ways to
induce photo degradation, which have in common the
formation of radicals initiated by the absorption of light.
Cellulose acetate is made from raw materials with a high
content of a-cellulose, but still contains some impurities
which might be responsible for the absorption of light in
the far UV light region with wavelengths shorter than
280 nm range [52–54]. Cellulose acetate has an absorption
at approximately 260 nm which is attributed to ketonic
carbonyl groups [53]. In consideration of the fact, that the
sunlight reaching earth’s surface after being filtered by the
atmosphere has a lower cut-off of approximately 300 nm,
one might conclude that cellulose acetate does not significantly photo degrade in a natural environment. This is
only valid if other factors like air, water and contaminations are neglected. Secondary mechanisms are important
in the photo degradation of cellulose acetate, which comprise other substances absorbing light and generating radicals for reacting with the cellulose acetate structure, these
include photocatalytic oxidation or photosensitized degradation. The two latter routes can enhance the photo degradation of cellulose acetate significantly if suitable
additives are applied. The degradation of pure cellulose
acetate by irradiation with light in the far UV-range
(k \ 300 nm) and the regarding studies are helpful in
obtaining an understanding of the general photo degradation mechanism.
Degradation by Far UV-Light
The degradation by direct irradiation of the solid material
has been studied on powder, film and fibers. Several
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analytical Y]