Chemistry Reference
In-Depth Information
Since DPC is a composition of resin - dye with dyeing component content from 100 up
to 50%, then the role of dye thermal stability is high, and it is desirable that resin nature in
DPC should be the same as that of granulate being dyed.
For stock dyeing no more than 0,1-0,5 weight % is introduced, as such amount of dye
cannot influence intermolecular interaction, chain regularity and polyester crystallinity [288].
At present new directions in modification are being developed using ultradispersed
powders-fluorenes, being closed molecules, Cn, where n=60, 70, 80… They have crystalline
structure and melt at the temperature above 237
0
C, but still technology of their production is
complex and inefficient [288]. Over the last years chemistry of polymers with conjugated
system (PCS) developed into separate field of polymer science [289].
Problems of chemistry and physico-chemistry of PCS attracted attention not only of
researchers working in the field of theoretical chemistry and physics but also researchers,
working in the field of polymer modification [290].
Compounds, in whose molecule frequent repetition of groups and bonds, causing
delocalization of valent electrons, is realized, are called polyconjugated systems.
A great number of substances with conjugated system, differing in type of conjugation
and also the nature of heteroatoms and atomic groups in the main and side chains, has been
synthesized at present. In this connection there has been suggested division of PCS into the
following types [289]:
1 - PCS characterized by π, π - electron interaction in the main chains;
II - PCS characterized by interaction of π-electrons and non-distributed d-electrons;
III - PCS characterized by interaction of π-electrons with d-orbitals.
PCS of the II type are the most interesting as modifiers. Many types of polymers belong
to this type. Their chains contain heteroatoms N, O, S with non-distributed π-electrons.
Among them are: polybenzimidazoles, thiazoles, thiadiazoles, polymers of hydrocyanic acid;
PCS with end heteroatoms - polymethynes, cyan dyes and their analogs, PCS with repeated
heteroatoms in conjugated chains - polyazines, polyschiff bases, polymeric azo- and
diazocompounds and so on.
The most widespread modifiers for polymers are salycyddienamines, which play the role
of light stabilizers and deactivators of metals being in the polymer.
It is known that aromatic substances, containing heteroatoms of nitrogen, may have
modifying effect on different polymers. Some derivatives of carbosol, according to literature
and patent data, may be both light stabilizers and antioxidants in oxidative destruction of
polymers.
From the series of highmolecular compounds the most interesting are polyconjugated
azomethine compounds (PAC), stabilizing activity of which has been studied in the works
[291, 292]. It is proved in these works that stabilizing effect is achieved at relatively small
concentrations of azomethines. In the work [162] the author comes to a conclusion that at
small concentrations azomethines work as inhibitors of radical processes, besides, they are
ultra-violet absorbers. It should be noted that azomethines display light protective action both
in vacuum and in the air.
Inhibitive action of PCS data is connected with the presence of both conjugated carbon-
nitrogen bonds and end amine groups, moreover inhibitive activity of azomethines increase as
conjugated chain grows longer [293].
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