292 Science and Human Welfare
of them is a chemical duplicate of natural crude rubber. Of
these six varieties, four of them, namely, Thiokol, Neoprene,
Koroseal, and Butyl, originated in this country.
The several types of synthetic rubber being marketed
under the name “Thiokol” are the result of research initiated
in early 1920. It is produced by the Thiokol Corporation
from the поп-critical materials, ethylene, sulphur, and salt.
The basic chemical reaction involved is that between sodium
polysulphide and ethylene dichloride. Thiokol is proving to
be a very satisfactory tire-tread material and may be the
answer to required retreads.
About ten years ago du Pont was actively engaged in a
search for a method of making butadiene rubber from
acetylene. In the course of the research the acetylene was
treated with hydrochloric acid giving a rubbery material.
The resultant “Neoprene” is now produced by the poly-
merization of the addition-product of vinyl acetylene and
hydrogen chloride. This new material found its way into
literally thousands of different products where it proved of
inestimable value. It was used despite the ready availability
of natural rubber and despite a substantial difference in
price. Since early in 1941 it has been so much in demand that
it was necessary to place it under mandatory priority con-
trol. Engineers use it in the form of molded goods, as dia-
phragms, belting, lining in oil hose, in the construction of
barrage balloons, and for heavy-duty tires.
Goodrich’s Koroseal is produced by the polymerization of
vinyl chloride with itself or with other compounds like vinyl
acetate. Its distinction is resistance to chemical attack. But
it lacks elasticity. It is used by the ton for cable covering on
battleships because it will not burn.
Another type of rubber is based upon the dehydrogenation
of isobutane, obtained from natural or cracked gases, to