Sulfur vulcanization sulfur is not miscible in the polymer prior to vulcanization and attention is paid to prevent sulfur bloom, where it migrates to the surface of the article. Accelerators act much like catalysts allowing vulcanisation to be performed cooler yet faster and with a more efficient use of sulfur. They achieve this by reacting with and breaking the sulfur ring to form a reactive intermediate, referred to as a sulfurating agent. This in turn reacts with cure sites in the rubber to bring about vulcanization. There are two major classes of vulcanization accelerators: primary accelerators and secondary accelerators (also known as
Kraton (polymer) Kraton (polymer) Kraton is the trade name given to a number of high performance elastomers manufactured by Kraton Polymers (), and used as synthetic replacements for rubber. Kraton polymers offers many of the properties of natural rubber, such as flexibility, high traction, and sealing abilities, but with increased resistance to heat, weathering, and chemicals. It was first made by the chemical division of the Shell Oil Company in the 1950s, under the technical leadership of Norman R. Legge. Shell sold its Kraton polymers business to private equity firm Ripplewood Holdings in March 2001. Kraton polymers are styrenic block copolymer (SBC)