Thiokol is a trade mark for various organic polysulfide polymers. Thiokol polymers are used as an elastomer in seals and sealants. The distinction between the polymers first commercialized by the Thiokol Corporation and subsequent polysulfide materials is often unclear.
Preparation and structureEdit
A variety of thiokols are recognized. Typically they are prepared by the combination of 2-chloroethanol, formaldehyde, and sodium polysulfide (Na2Sx). The chloroethanol is produced in situ from ethylene oxide and hydrogen chloride. The rank x of the polysulfide is an important variable. Crosslinking agents are used, such as 1,2,3-trichloropropane. An idealized polymer is represented by this formula HS(CH2CH2OCH2OCH2CH2SS)nCH2CH2OCH2OCH2CH2SH. Thiol-terminated resins can be cured oxidatively.
History and etymologyEdit
In 1838, Swiss chemists reported the preparation of hydrophobilic rubbery materials by the alkylation of sodium polysulfide with 1,2-dichloroethane. In 1926 chemists Joseph C. Patrick and Nathan Mnookin further developed this class of materials, which first achieved commercial success as sealants for fuel lines, exploiting the solvent resistance of these materials. The first production plant was started in 1948 in Elkton, Maryland. The company Thiokol was founded in 1929 to produce these polymers. In the 1940s, thiol-terminated liquid resins were produced. Curing could be effected oxidatively, e.g. using lead oxides and later perborates. Thiokol polymers were used as a binder in solid rocket fuel, a commercial success.
The name "Thiokol" derives from the Greek words for sulfur and glue.
- Mark S. M. Alger (1997). Polymer Science Dictionary. Springer. p. 569. ISBN 978-0-412-60870-4.
- Vietti, David; Scherrer, Micheal (2000), "Polymers Containing Sulfur, Polysulfides", Kirk-Othmer Encyclopedia of Chemical Technology, New York: John Wiley, doi:10.1002/0471238961.1615122522090520.a01, ISBN 9780471238966
- Edwards, Douglas C. (2001). "Liquid Rubber". In Bhowmick, Anil K.; Stephens, Howard (eds.). Handbook of Elastomers, Second Edition (First ed.). Marcel Dekker Inc. p. 135. ISBN 0-8247-0383-9. Retrieved 8 February 2015. CS1 maint: discouraged parameter (link)