Abstract
Abstract
Vulcanization of styrene-butadiene rubber, as accelerated by a series of sulfenamides and sulfenimides prepared from various aromatic heterocyclic thiols and various aliphatic amines, was studied using the curemeter under isothermal conditions. Further studies using MOPAC AM1 semiempirical quantum mechanical calculations and CODESSA QSAR software yielded excellent correlations of molecular descriptors of accelerators or accelerator thiolate zinc complexes to the onset of cure and maximum rate of vulcanization. The QSAR results support previously proposed mechanisms describing the origin of scorch delay for the delayed action, fast curing sulfenamide accelerators. In addition, the results support a carbanionic concerted mechanism for the sulfurization and crosslinking reactions.