Sulfur vulcanization

This article is about processes specifically based around sulfur. For a wider range of processes, see Vulcanization.
Worker placing a tire in a mold before vulcanization

Sulfur vulcanization is a chemical process for converting natural rubber or related polymers into materials of varying hardness, elasticity, and mechanical durability by heating them with sulfur[1] or sulfur-containing compounds.[2] Sulfur forms cross-linking bridges between sections of polymer chains which affects the mechanical and electronic properties.[1] Many products are made with vulcanized rubber, including tires, shoe soles, hoses, and conveyor belts. The term vulcanization is derived from Vulcan, the Roman god of fire.

The main polymers subjected to sulfur vulcanization are polyisoprene (natural rubber, NR), polybutadiene rubber (BR) and styrene-butadiene rubber (SBR), and ethylene propylene diene monomer rubber (EPDM rubber). All of these materials contain alkene groups adjacent to methylene groups.[3] Other specialty rubbers may also be vulcanized, such as nitrile rubber (NBR) and butyl rubber (IIR). Vulcanization, in common with the curing of other thermosetting polymers, is generally irreversible. Efforts have focussed on developing de-vulcanization (see tire recycling) processes for recycling of rubber waste but with little success.

  1. ^ a b James E. Mark; Burak Erman, eds. (2005). Science and technology of rubber. p. 768. ISBN 978-0-12-464786-2.
  2. ^ Akiba, M (1997). "Vulcanization and crosslinking in elastomers". Progress in Polymer Science. 22 (3): 475–521. doi:10.1016/S0079-6700(96)00015-9.
  3. ^ Coran, A.Y. (2013). "Chapter 7 - Vulcanization". The Science and Technology of Rubber (Fourth ed.). Elsevier. pp. 337–381. doi:10.1016/B978-0-12-394584-6.00007-8. ISBN 978-0-12-394584-6.