Sulfur combined in the vulcanization network in a number of ways: 1. as crosslinks, it may be present as monosulfide, disulfide, or polysulfide 2. as pendant sulfides 3. cyclic monosulfides and disulfidesIn an unaccelerated rubber-sulfur vulcanisate, the number of sulfur atoms for each crosslink formed has been estimated at 40 - 45.Discovery of mercaptobenzthiazole (MBT) in 1921 allowed reduction in cure times to 5-10 minutes at 140º C, however the compound tends to be scorchy (i.e. premature vulcanization).