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
Rubber technology 1844, but is a process restricted to polymer chains having a Double bond in the backbone. Such materials include natural rubber and polybutadiene. The range of materials available is much wider however, since all polymers become elastomeric above their Glass transition temperature. However, the elastomeric state is unstable because chains can slip past one another resulting in creep or stress relaxation under static or dynamic load conditions. Chemical cross links add the stability to the network that is needed for most practical applications. WORKER PROCESSING RUBBER Methods for processing rubber include mastication and various operations like mixing, calendering, extrusion, all