N-Sulfonyl-sulfilimines which undergo a thermal elimination to form N-alkyl (or aryl)thiosulfonamides act as premature vulcanization inhibitors, apparently by the same mechanism as the thiosulfonamides. S,S-di(isopropyl)-N-(p-toluenesulfonyl) sulfilimine was of particular interest due to its good inhibitory activity, ease of preparation, excellent stability, and resistance to bloom.
The 1,2-addition of certain N-chlorothioamides to the olefinic sites of EPDM produces modified polymers which exhibit improved covulcanization in blends with polydiene rubbers. A mechanism is postulated in which the modified EPDM retards the cure of the polydiene phase and at the same time is itself activated toward crosslinking. Model compound data are presented to support these views.
The activity of the thiosulfonamides and dithiotrichloromethanes as retarders is apparently a result of their ability to function as BTSH trapping agents. The effect of substituents on retarder efficiencies seems consistent with a mechanism involving a three-way competition between crosslinking, retardation, and decomposition of retarder to non-functional products. The key reaction responsible for trapping BTSH probably involves a nucleophilic displacement. Substituents which favor this type of displacement increase efficiency when they are on the portion of the retarder molecule which combines with BTSH; when they are on the portion which becomes the leaving group, they evidently promote decomposition, causing a net decrease in retarder efficiency.
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