Chemistry Reference
In-Depth Information
Investigation of mechanical properties of modified and initial CDA before irradiation, as
it is seen from Table 25, shows that they are similar in properties. However, irradiation exerts
different effect on CDA and its modified analogs.
It follows from Table 25 that modification of CDA considerably increases resistance of
this type of compounds to severe ultra-violet irradiation. Since light waves range 300-400nm
is the most dangerous for CDA then it may be assumed that light stabilizing action of this
compound is based on the absorption mechanism of light absorption. The fact of slight
increase of DTIU stabilizing activity at considerable increase of its content in polymer attracts
attention and this indirectly indicates inhibitive activity of DTIU during oxidative destruction
of polymer and is proved by studying its thermal oxidation.
Table 25. Effect of ultra-violet irradiation on mechanical properties of the films of
modified and initial CDA
DTIU content
(% of polymer mass)
Degree of
conservation (%)
before irradiation
after irradiation
mm2
%
mm2
%
0
637,4
3,62
310,4
0,45
48,7
12,8
0,2
654,0
5,48
379,5
2,42
57,8
44,2
1,0
601,5
4,06
2,28
88,7
56,2
3,5
622,3
3,86
75,0
24
92,5
58,2
Investigation of the kinetic of mass loss at thermooxidative destruction of modified CDA
showed that modification increases its stability to the heating at elevated temperatures (Figure
2.33). Loss of mass of modified CDA in much less in comparison with initial values during
prolonged heating of polymer samples in the air (150°-200°C). These conclusions are proved
by the results of complex thermogravimetric analysis (TGA).
From the curves of TGA it follows that temperature of decomposition of modified CDA
is 20°C higher that of non-modified one. Presence of two exthermical peaks on the DTA
curves of initial CDA and absence of such peaks of modified polymer at the temperatures
240°C and 290°C are seen here.
May be this difference is connected with the fact that the number of OH-groups, being
subjected to dehydration during heating of initial CDA are mush larger than of modified one.
Effective activation energy, calculated according to the method of Freeman-Karrol, of
modified CDA was higher by 504 J/mole in comparison with initial polymer.
On the whole we may make a conclusion that expected effect of photo- and thermo-
stability appeared to be slight.
Search WWH ::
Custom Search