STABILIZATION AND MODIFICATION OF POLYCAPROAMIDE - Photochemical Reactions in Heterochain Polymers - page 8

investigated for many compounds of one class. There are no reliable numerical data on the
expediency of use of many organic compounds as ultra-violet absorbers and suppressors of
polymer excited states, though necessity in such investigations was repeatedly noted at
conferences and symposiums on ageing and stabilization of polymers [48-52].
Photo- and Thermostabilizers of Polyamides
A great number of scientific publications in our country and abroad stress the interest in
this problem [2, 42, 10, 46, 53-58]. Metallo-organic stabilizers have found their application
for stabilization of polymer materials from PA. In the first place these are compounds of
metals with variable valency: copper, lead, zinc and so on. Metal copper, salts of univalent
and bivalent copper of inorganic and organic acids [55], mixture of copper with hydrogenised
bisphenol and triphenilphosphate [56] from the metal compounds, used as photo - and
thermoinhibitors of PA oxidation, are mentioned in major patents. However, these
compounds in are badly combined and unevenly distributed in polymer and this makes worse
their stabilizing activity because of their low migration in polymer matrix.
Copper macrocyclic complexes of tri - and zoindobenzol in the presence of potassium
iodide, known as stabilines [57, 58] (for example, stabiline 10, stabiline A), inhibiting
destruction processes and facilitating the formation of more favourable polymer structure are
worth of paying attention to. Copper complexes with tiadiazolysoindole and
tiadiazolysoindolphenilene in the mix with halogen - , amino - or phosphorus compounds
have found their application [59],
as copper complexes on the basis of polyhexoazocyclanes [60], where it is shown, that
introduction of these compounds reduces photo - and thermal destruction of PA at the
expence of the presence of copper, halogens, NH - groups in stabilizer.
Interesting thermo - and light stabilizer is the product of CuCl 2 reaction with 2 -
mercaptobenzimidazole [61].
Black, as internal filter regarding ultra-violet light [42], is used with high efficiency.
Besides, since black usually contains stable free radicals, it may react with photochemically
formed active polymer centres, in such a way reducing the rate of the process of chain
continuation [62]. Black is also used as suppressor of triplet and singlet polymer states.
Black's different stabilizing activity is displayed depending on the nature (furnace,
channel, thermal, lamp, acetylene black) and the size of the particles.