Sulfur vulcanization been uncertainly as to whether it proceeds in a radical or ionic manner. The reactive sites, often referred to as 'cure sites', are unsaturated groups such as alkenes and allyls. During vulcanization, sulfur bridges are formed between these sites, crosslinking the polymer. These bridges may consist one or several sulfur atoms. Both the extent of crosslinking and the number of sulfur atoms in the crosslinks strongly influences the physical properties of the rubber produced: Sulfur, by itself, is a slow vulcanizing agent and does not vulcanize synthetic polyolefins. Even with natural rubber, large amounts of sulfur as well as high
Sulfur trioxide Sulfur trioxide Sulfur trioxide (alternative spelling sulphur trioxide) is the chemical compound with the formula SO, with a relatively narrow liquid range. In the gaseous form, this species is a significant pollutant, being the primary agent in acid rain. It is prepared on an industrial scale as a precursor to sulfuric acid. In perfectly dry apparatus, sulfur trioxide vapor is invisible, and the liquid is transparent. However, it fumes profusely even in a relatively dry atmosphere (it has been used as a smoke agent) due to formation of a sulfuric acid mist. This vapor has no odor but is extremely