Stabilization of Polyolefins Against Oxidative Destruction

In this case an inhibitor radical, incapable of continuing the oxidation chain, is formed (see Chapter I). 

Since the antioxidant terminates the kinetic chains during oxidation of a pol3oner (reacts with ROO or decomposes hydroperoxides, thereby nullifying the possibilily of chain development), the external manifestation of its influence on the process consists of lengthening the period during which the reaction proceeds before autocatal3rtic acceleration in this case the antioxidant is consumed. At the end of this period, the process of polymer oxidation develops with autoacceleration, at practically the same rates as in the absence of the antioxidant, which is well illustrated by Fig. 50 [22]. 

Frequently no appreciable absorption of oiygen is observed at the initial stage of the development of the reaction (before autocatalysis),as in the case of the addition of benzidine (curve 2 in Fig. 50) and neozone D (curve 4), or diphenylamine (curve 3), and especially sulfur-containing compounds slow absorption of oxygen occurs during this period. It is assumed that in the latter case the basic role of the antioxidant reduces to the decomposition of hydroperoxides, which accumulate as a result of the reactions of the steady-state process of development of oxidative chains. 

In the first case the induction period of the oxidation, defined in most experimental work as the time during which the oxygen pressure in the system decreases by a quite definite small quantity (1-5 mm Hg), coincides with the beginning of the autocatalytic acceleration of the reaction in the second case it is always smaller. As a result of this, an inhibition of the oxidation process is observed after the end of the induction period. 

As a result of the fact that the introduction of antioxidants leads to a very great lengthening of the induction period, the physicomechanical 

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