Chemistry Reference
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second - dye transfer into undyed PETP sample, the third - dye transfer into the matrix -
viscose fibre.
Since operation of polymer goods is carried out as a rule, under conditions of variable
humidity of environment; it was necessary to evaluate sorption properties of obtained PETP -
fibres. In our case to describe sorption processes the following equation was chosen [307,
308]:
α = α
0
exp [(-RT ln ln/E)' - α (T-T)]
(5)
where α - value of equilibrium sorption, α
0
- maximum sorption from vapour phase, R -
universal gas constant, T - temperature K, h - relative pressure of sorbate vapours, E -
characteristic energy of absorption, T
0
- temperature K, at which constants of the equation
were defined.
Choice of this equation is caused by the fact, that it satisfactorily described sorption
isotherms not only of water, but of organic substances with root-mean-square error δ<13%,
and it was successfully used for calculating sorption isotherm in systems PETP - methanol,
PETP - phenol, PETP - water.
As sorption characteristics of irradiated and unirradiated dyed PETP - fibres, calculated
from isotherms of water sorption (Table 31), show, sorption of water by dyed samples is
higher than in initial ones, that may be connected with plasticizing action of hexaazocyclanes
additives and also with the effect of additives on the character of mobility in PETP chains
[309, 310].
Maximum sorption of irradiated fibres is considerably lower which is probably caused
either by polymer construction seal in the process of irradiation, similar to the seal at thermal
treatment, or by structurization taking place at severe irradiation and being similar to
structurization in other polymers, namely, polystyrene [311].
All studied light stabilizers (Figure 3.1.) have >C=N- group. Photochemical reactions of
>C=N- groups are similar to photochemical reactions of carbonyl groups [46]. That is why
primary photochemical reaction of stabilizer should be breakage of H atom from substrate by
excited state of >C=N- group.
Rate of deactivation of excite4d state for all HC - stabilizers being studied is much
greater than the rate of intramolecular proton transfer.
It has been noted lately [14] that within the limits of one class of stabilizers change of
their structure, introduction of substituents weakly change their reaction ability in solid
polymer. Obtained by us results do not agree with this supposition, as HC-1 and HC-2 have
different effect on thermal and thermooxidative stability of PETP - fibres.
Table 31. Value of sorption for irradiated and unirradiated PETP samples
Dye
Unirradiated
Irradiated
α
0
, %
E, kJ/mole
α
0
, %
E, kJ/mole
Without dye
1,41
1,60
-
-
HC-1
3,74
2,60
0,97
2,38
HC-2
2,70
1,53
1,54
3,53
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