Chemistry Magic 155 



"Bathtub" Rubber 



Butyl rubber, a copolymer of isobutylene and small amounts 

 of other unsaturated hydrocarbons such as butadiene or iso- 

 prene. Flexon, a modification of this type, is called "bathtub 

 butyl" because it can be made with comparatively simple 

 equipment. Butyl is spoken of as "an ace in the hole" in our 

 synthetic program, and could be produced at low cost quickly 

 from abundant materials to replace natural rubber in many 

 applications. Standard Oil of New Jersey controls the proc- 

 ess. Butyl's general resistance to deterioration is good, but its 

 physical properties are lower than those of natural rubber. 

 It may be used to advantage in applications where resistance 

 to chemicals and oxidation (it is one of the few materials 

 resistant to the poison gas lewisite) are more important fac- 

 tors than tensile strength and elasticity. 



Thiokols of types A, B, and FA, made from ethylene di- 

 chloride and sodium tetrasulfide or from dichloroethyl ether 

 and sodium tetrasulfide or from modifications and combina- 

 tions of the two. They were developed by the Thiokol Cor- 

 poration and are now being manufactured by the Dow Chem- 

 ical Company for the Thiokol Corporation, which handles the 

 sale. (Thiokol RD, a Buna N synthetic rubber, must not be 

 confused with this group of Thiokols.) The Thiokols have 

 better resistance to aromatic hydrocarbons (such as benzene, 

 naphthalene, and toluene, which cause rubber to swell and 

 deteriorate) than natural rubber or other synthetic rubbers. 

 They do not, however, have as high physical properties as the 

 other synthetics. Where resistance to deterioration is more 

 important than resilience, tensile strength, resistance to abra- 

 sion, and extremes of temperature, as in certain industrial uses, 

 the Thiokols have been successfully substituted for natural 

 rubber. 



