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The reaction of polyisoprenes in oxidative radical processes

A. Tkáč and V. Kellö

Slovak Technical University, Bratislava

 

Abstract: The thermooxidn. of polyisoprene (I) and primary and secondary factors of its stability are described. The length of the induction perfod of the oxidn. is related to the amts. of decompn. products of catalytic complexes. As long as the polymer prepd. is not sufficiently stable, even an effective elimination of traces of Ti and Al does not increase its stability. The stability is closely related to the process ending the polymerization, i.e. to the no. of residual active centers on the polymer chain. This was proven by a study of the oxidn. of I that had been enriched with radicals over the ordinary stationary concn. For I without inhibitors contg. a relatively high amt. of Ti, under the conditions of the thermal generation of radicals, the induction period of the oxidn. is considerably lengthened. This new effect can be explained by a removal of active centers in the inert medium at 140° in the presence of residues after decompn. of the catalysts. The radical mechanism is affected by stable free radicals, of the type α,α'-diphenyl-β-picrylhydrazyl, as traps, which decrease the level of macroradicals. In their presence, oxidn. occurs with short kinetic chains, which leads to a considerable decrease in the steady-state portion of the kinetic curves of oxidn. and at the same time to a lengthening of the induction period. After exhaustion of the radical trap, the oxidn. rate suddenly increases, which is shown on the kinetic curve by a 2nd wave.

Full paper in Portable Document Format: 174a237.pdf (in Slovak)

 

Chemical Papers 17 (4) 237–247 (1963)

Wednesday, April 17, 2024

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