Reaction of Radical Acceptors with Polymer Radicals formed by Mechanical Degradation of Vulcanizates

The authors investigated, by the EPR method, the kinetics of the accumulation and subsequent deterioration of polymer radicals, resulting from the mechanical degradation of sulfur and peroxide vulcanizates of SKMS-3 ARKM-15 rubbers at 80 ° K. The reaction of these radicals with a number of acceptors were also studied. The polymer radicals, independently of their nature, will deteriorate at temperatures near the Tg. Polysulfide radicals are completely destroyed at 240–250° K, the hydrocarbon radicals at 220–235° K, and the peroxide ones at 200–210° K. The peroxide radicals will react, at 80° K, with Ionol and alkylphenol disulfides to form phenoxy radicals, and with trichlorothiophenol to produce thiol radicals, but will not react with the stable nitroxide radicals or with di-(trichlorophenyl) disulfides. The carbon free radicals will react, at 150–200 ° K, with trichlorothiophenol and with alkylphenol disulfides, resulting in formation of polysulfide radicals, and, at 80° K, they will react with stable nitroxide radicals to form 2,2,6,6-tetramethyl-4-hydroxypiperidyl. The polysulfide radicals, within a temperature range of 80 to 250° K, do not react to any appreciable degree with any of the radical acceptors investigated.