Vulcanization of Elastomers. 38. the Reactivity of Synthetic Rubbers. I

Abstract Investigations relating to the development of other than conventional procedures for vulcanizing synthetic rubbers, especially cis-1,4-polybutadiene, are reported. The results were as follows: 1. cis-Polybutadiene and trans-polybutadiene containing 2% and more of 1,2 addition can be crosslinked to a certain extent by means of dibenzothiazolyl- or dibenzimidazolyldisulfide. 2. cis-1,4-Polyisoprene undergoes a much lower degree of crosslinking with the above disulfides. 3. The physical properties of vulcanizates are considerably improved if the molecules of the added disulfides contain groups which react with isocyanates. When diisocyanates are incorporated, supplementary crosslinking sites are formed. 4. The crosslinking of cis- and trans-polybutadiene via DBIS and Desmodur 15, in the absence and presence of black is described in more detail. The usual physical properties are determined and compared with those obtained when sulfur is used as the vulcanizing agent.