A contribution to the theory of accelerated sulphur vulcanization of natural rubber and polybutadiene BR with tetramethyl thiuram disulphide and bis(2‐benzothiazolyl) disulphide

Abstract

AbstractA number of simple natural rubber (NR) and polybutadiene (BR) formulations were vulcanized in a differential scanning calorimeter. From the shapes of the exothermal cure curves the interaction of curatives can be examined. It is suggested that polysulphidic‐accelerator‐terminated pendent groups could either crosslink, or be chelated with zinc ions. The latter reaction allows interaction with accelerator molecules to reform the unchelated pendent group, and a zinc accelerator complex, that, in turn, can react with sulphur and rubber molecules to give pendent groups. Differences in the behavior of NR and BR are attributed to the relative rates of these two reactions in the elastomers. Bis(2‐benzothiazolyl) disulphide does not react with zinc, and it is suggested that it coordinates with the zinc dithiolate accelerator complex, increasing its activity.