Stabilization and Modification of Polycaproamide

Aliphatic polyamides (PA) and products on their base are polymers with low stability to ultra-violet irradiation and under the effect of solar radiation they destruct less than in a year [1]. In natural conditions ultra-violet part of solar spectrum with wave-length 290-350 nm is more dangerous for these polymers, though aliphatic PAs in this field have very weak absorption of chromophore amide group [2, 3], That is why while examining the problem of PA phototransformations, unlike other polymers, both possibility of light absorption by impurities and self-absorption should be taken into consideration [4], 

Mechanisms of aliphatic PA photooxidation under light action in the conditions of amide group absorption [4] where studied. These reactions way flow under the action of short-wave light which boundary at the Earth s surface is 290 nm. The main result of investigations was discovery of the role of radical - CONHCHCH - (Ri ), being the precursor of all basic products of alkylamide oxidation, for example, RC O and Pi, formed at primary photochemical process of photodissociation of amide bond according to the reaction  

Photolysis of PA-6 in solid state by light 253,7 nm is considered in works [7,8] gas composition of products is also investigated and this shows the presence of CO-groups. 

Analysis of the products of nonsensibilized oxidation of PA and model amides proved special role of radical Pi which, being formed by stage of H breaking from a- methylene group, led to further autooxidation according to a following scheme [10]  

It has been supposed that probability of radical decay of Pi OOH is small and photodecay of peroxides does not make considerable contribution to formation of radicals and products of oxidation, and appearance of radicals Pi and P1O2 in PA leads to efficient breakage of macromolecules. Under some conditions there is possibility for quantitative transformation of redicals Pi and P1O2 and fonnation of Pi with quantitative yield from radicals of other types. 

---