Formation of polymer hydroperoxides

A polymer peroxy radical reacts with another polymer molecule and abstracts a hydrogen atom  

In many circumstances the propagation rate coefficient kl6 is a composite for several possible reactions of peroxy radicals. The hydrogen abstraction reaction is sensitive to the conformation of the attacking radical and to polar and steric effects, and is dependent on temperature [289, 301, 579]. Peroxy radicals as a class are relatively selective electropholic species abstracting tertiary hydrogen in preference to secondary and primary. 

Polymeric hydroperoxides are the major product of low temperature oxidation [Refs. 46, 113,115, 148, 189, 191, 193,195,196, 300]. Yields of hydroperoxides in oxidized polypropylene exceed 40%, and more than half that amount is contained in low molecular weight degradation products. It was shown that isolated hydroperoxide groups in thermally oxidized polypropylene constitute less than 10% of the total hydroperoxide concentration, and the majority of the polypropylene hydroperoxide groups occur in dimers, trimers, or longer sequences [148]. 

The absorption band at 3520 cm-1 due to the unbonded hydroperoxide group (—OOH) is very weak, whereas the absorption band at about 3380 cm-1 is common to the bonded hydroperoxide and hydroxyl (—OH) groups. For this reason it is difficult to determine quantitatively the content of hydroperoxide groups by IR absorption spectroscopy. Mitchel and Perkins [427] devised a rfew method, based on the reaction with S02 

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In propagation, the degradative chain is prolonged by the follbwing methods 2.2.2.1 Formation of Polymer Hydroperoxide... 

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