''Thiokol'' is a

trade mark A trademark (also written trade mark or trade-mark) is a type of intellectual property consisting of a recognizable sign, design, or expression that identifies products or services from a particular source and distinguishes them from others. ...

for various organic polysulfide polymers. Thiokol polymers are used as an

elastomer An elastomer is a polymer with viscoelasticity (i.e. both viscosity and elasticity) and with weak intermolecular forces, generally low Young's modulus and high failure strain compared with other materials. The term, a portmanteau of ''elastic p ...

in seals and

sealant Sealant is a substance used to block the passage of fluids through openings in materials, a type of mechanical seal. In building construction ''sealant'' is sometimes synonymous with ''caulking'' and also serve the purposes of blocking dust, s ...

s. The distinction between the polymers first commercialized by the Thiokol Corporation and subsequent polysulfide materials is often unclear.

Preparation and structure

A variety of thiokols are recognized. Typically they are prepared by the combination of

2-chloroethanol 2-Chloroethanol (also called ethylene chlorohydrin or glycol chlorohydrin) is an organic chemical compound with the chemical formula HOCH2CH2Cl and the ''simplest'' beta-halohydrin (chlorohydrin). This colorless liquid has a pleasant ether-like od ...

formaldehyde Formaldehyde ( , ) (systematic name methanal) is a naturally occurring organic compound with the formula and structure . The pure compound is a pungent, colourless gas that polymerises spontaneously into paraformaldehyde (refer to section F ...

, and sodium polysulfide (Na₂S_''x''). The chloroethanol is produced in situ from ethylene oxide and

hydrogen chloride The compound hydrogen chloride has the chemical formula and as such is a hydrogen halide. At room temperature, it is a colourless gas, which forms white fumes of hydrochloric acid upon contact with atmospheric water vapor. Hydrogen chloride ga ...

. The rank ''x'' of the polysulfide is an important variable. Crosslinking agents are used, such as

1,2,3-trichloropropane 1,2,3-Trichloropropane (TCP) is an organic compound with the formula CHCl(CH2Cl)2. It is a colorless liquid that is used as a solvent and in other specialty applications. Production 1,2,3-Trichloropropane is produced the addition of chlorine t ...

. An idealized polymer is represented by this formula HS(CH₂CH₂OCH₂OCH₂CH₂SS)_''n''CH₂CH₂OCH₂OCH₂CH₂SH. Thiol-terminated resins can be cured oxidatively.

History and etymology

In 1838, Swiss chemists reported the preparation of hydrophobic rubbery materials by the alkylation of sodium polysulfide with 1,2-dichloroethane. In 1926 chemists Joseph C. Patrick and

Nathan Mnookin Thiokol (variously Thiokol Chemical Corporation(/Company), Morton Thiokol Inc., Cordant Technologies Inc., Thiokol Propulsion, AIC Group, ATK Thiokol, ATK Launch Systems Group; finally Orbital ATK before becoming part of Northrop Grumman) was an ...

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 Maryland ( ) is a state in the Mid-Atlantic region of the United States. It shares borders with Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware and the Atlantic Ocean to ...

. The company

Thiokol Thiokol (variously Thiokol Chemical Corporation(/Company), Morton Thiokol Inc., Cordant Technologies Inc., Thiokol Propulsion, AIC Group, ATK Thiokol, ATK Launch Systems Group; finally Orbital ATK before becoming part of Northrop Grumman) was an ...

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 A solid-propellant rocket or solid rocket is a rocket with a rocket engine that uses solid propellants Rocket propellant is the reaction mass of a rocket. This reaction mass is ejected at the highest achievable velocity from a rocket engine ...

fuel, a commercial success. The name "Thiokol" derives from the Greek words for sulfur and glue.

References

Elastomers Inorganic polymers Sulfur compounds {{polymer-stub