When Goodyear first achieved the vulcanization
of rubber, 8 parts of sulfur were used per 100 parts
of rubber, and the vulcanization process needed 5 h
at 140C. After that, the addition of zinc oxide (ZnO)
allowed the vulcanization time to be reduced to 3 h.
Subsequently, the vulcanization time was significantly
reduced to 1–3 min by the use of only 0.5 phr
of an accelerator.2