Full definition
A chemical additive that dramatically increases the speed of sulfur vulcanization while reducing the required temperature and time, making rubber manufacturing economically viable. Without accelerators, sulfur vulcanization of NR takes 5-6 hours at 140°C; with accelerators, 5-20 minutes. Major families: thiazoles (MBT, MBTS — fast cure, general purpose), sulfenamides (CBS, TBBS — delayed action/scorch safety, most widely used industrially), thiurams (TMTD, TETD — ultra-fast, used as secondary accelerator or sulfur donor), dithiocarbamates (ZDEC, ZDBC — ultra-fast, for low-temperature cure and latex). Dosage: typically 0.5-2.5 phr. Used in combination with activators (ZnO + stearic acid). Selection depends on compound type, cure speed, scorch safety, and end-product requirements. Per ASTM D4818 for classification. Accelerator chemistry is a core competency of rubber compounders.