Full definition
Chemical compound added to a rubber formulation (0.5-2.5 phr) to reduce sulfur vulcanization time from hours to minutes while lowering the required cure temperature. Major families: thiazoles (MBT, MBTS — moderate speed, general purpose), sulfenamides (CBS, TBBS — delayed action with excellent scorch safety, the most widely used class in industrial rubber), thiurams (TMTD, TETD — ultra-fast, used as secondary accelerator or sulfur donor in efficient/semi-efficient cure systems), and dithiocarbamates (ZDEC, ZDBC — ultra-fast, for low-temperature cure and latex products). Accelerators always work with zinc oxide + stearic acid (activator system) and sulfur. Selection impacts scorch time (processing safety), cure rate, and final vulcanizate properties. Per ASTM D4818 classification. Binary and ternary accelerator combinations are common to optimize both processing and performance.