Insights into sulfur vulcanization from QSPR quantitative structure-property relationships studies

Vulcanization of styrene-butadiene rubber, as accelerated by a series of su lfenamides and sulfenimides prepared from various aromatic heterocyclic thi ols and various aliphatic amines, was studied using the curemeter under iso thermal conditions. Further studies using MOPAC AM1 semiempirical quantum m echanical calculations and CODESSA QSAR software yielded excellent correlat ions 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 sco rch delay for the delayed action, fast curing sulfenamide accelerators. In addition, the results support a carbanionic concerted mechanism for the sul furization and crosslinking reactions.