Hydroperoxide groups polyamides

Hydroperoxide groups can be generated previously on the Nylon monomer, e.g. oxidizing the tertiary carbon atom of the isopropyl group of the 5-isopropyl phthaloyl chloride with potassium permanganate. The corresponding polyamide can be grafted with styrene in a redox system (151). 

The concentration of hydroperoxide groups formed depends on the type of polyamide, e.g. it is higher in polyamide 12 (polydodecanamide) (18 mmol kg" ) than in polyamide 6 (polyhexanamide) or polyamide 11 (polyundecanamide) (2-4 mmol kg-1) [1321]. 

For other polymers, differentiation of hydroperoxide groups by reaction with nitric oxide is very limited. For example, polyamides react directly with nitric oxide, obscuring any products for oxidation of the polymer. Unsaturated polymers such as polybutadiene and polyisoprene also react directly with nitric oxide even at — 20°C, giving nitrocompounds which interfere with the identification of oxidation products. 

It has been found that the end groups play a major role in the rate of oxidation since carboxylic acid groups will catalyse decomposition of hydroperoxide and lower the temperature for the maximum rate of degradation by 60 C. In contrast polyamides terminated with amine end groups are more stable. 

Then a peroxide radical and hydroperoxides are formed at the site of stripping of the hydrogen atom. Water is obtained when the hydroperoxides decompose (see p. 16). In the thermal oxidation of polyamides, the liberation of water may lead to hydrolysis of the polymer and an increase in the number of terminal carboxyl groups. Decarboxylation gives carbon dioxide. In addition to decomposition of hydroperoxides, decomposition of peroxide radicals may also occur ... 

Aliphatic polyamides do not absorb light above 290 nm and photo-oxidative degradation of these polymers in that region can be initiated by the presence of such impurities as hydroperoxides, [47, 139] carbonyl groups [1869], a,j -unsaturated carbonyl groups [47, 65, 89, 99, 103] and traces of metal ions [236]. 

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