INSIGHTS INTO SULFUR VULCANIZATION FROM QSPR QUANTITATIVE STRUCTURE-PROPERTY RELATIONSHIPS STUDIES

Vulcanization of styrene-butadiene rubber, as accelerated by a series of sulfenamides and sulfenimides prepared from various aromatic hcterocyclic thiols and various aliphatic amines, was studied using the curemeter under isothermal conditions. Further studies usingMOPACAMI semiempirical quantum mechanical calculations and CODESSAQSAR software yielded excellent corrclations 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.