STABILIZATION AND MODIFICATION OF CELLULOSE DIACETATE - Photochemical Reactions in Heterochain Polymers - page 94

effect. This shows “shielding” effect of sulphur containing compounds, though their action as
oxidants cannot be excluded.

2.8. S TABILIZING BY M EANS OF C HEMICAL M ODIFICATION
OF CDA

Earlier Kargin V. made a hypothesis that on interesting method of stabilization is
chemical modification of polymer by addition of stabilizers according to active functional
groups of high-molecular compound. And though, on practical part, this method is less
promising, at is connected with the change of technological conditions of polymer production,
in some cases it is worth of paying attention to, since stabilizer washing-out during wet
treatments, its volatility in vacuum or at high temperature action are eliminated.
For this purpose CDA modification by its condensation with (diphenyl-p-trilisocynate)
urea (DTIU) was carried out according to the reaction:

Before hand testing of light stabilizing activity of DTIU while introducing it into a
polymer as mechanical additive was carried out. Data of Table 24 show that DTIU possesses
photostabilizing activity that gives the reason to consider the fact that its condensation with
CDA will improve light fastness of the latter.
Table 24. Effect of cellulose diacetate films ultra-violet irradiation on conservation of
viscosity characteristics. Distance from the irradiation source is 30cm,
time of exposure is 24 hours

DTIU content
(% of polymer mass)

Degree of viscosity
conservation (%)

Specific viscosity of polymer η spec

before irradiation after irradiation

0 2,00 0,46 29,0

2 2,00 1,46 73,0

4 2,00 1,60 80,0

Molecular weights of initial CDA and its modified analog were calculated according to
viscosimetric data with the use of formula [η]=KM α , where K = 0,19·10 4 and α = 1.03 4 . These
molecular weights before irradiation were M in = 62660 and M mod = 69020 respectively, and
after irradiation they were: M in = 23390 and M mod = 61940. The number of breaks after
irradiation, calculated on the basis of these data, of the initial CDA was 2,68 and of modified
analog it was 1,11.