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NATURAL AND SYNTHETIC RUBBERS 711

In 1941 the United States Government arranged with four rubber

companies to build synthetic rubber plants each with an initial capacity

of 2500 tons per year, to be increased eventually to 10,000 tons per

year for each plant.

About 1930 the E. I. du Pont de Nemours Company produced a new

synthetic rubber, neoprene, from the basic materials, coal, limestone,

and salt. Acetylene prepared from calcium carbide was changed in

the presence of catalysts (cuprous salts) to monovinyl acetylene,

was

HC^C—CH=CH2, which

heated with hydrochloric acid,

HCl, made from salt to produce

CL

chloroprene, HaC^-C—CH=CH2.

Chloroprene is polymerized to

Neoprene is

produce neoprene.

superior to natural rubber in its

resistance to hydrocarbon solvents,

to light, and to oxidation.

Unlike natural rubber it does not

require sulfur for vulcanization.

Neoprene is used to advantage

in the manufacture of hose for

any purpose where oil or other

hydrocarbons are likely to be

present, for conveyor belts, packing, printing rollers, electrical cables,

ignition wire, gloves, protective clothing, motor mountings, nonslip floor

wax, and many other products which are subjected to conditions that

quickly deteriorate natural rubber.

The Russians make a synthetic rubber

known as Sovprene, which is believed by some people to be similar

to neoprene. Sovprene is the name given to the Russian version of

neoprene.

A self-sealing rubber airplane

tank. (Courtesy of the United

States Rubber Company.)

In late 1941 the production of neoprene had been raised to

1,500,000 pounds per month, and a new plant was being erected by the

E. I. du Pont de Nemours and Company at Louisville, Kentucky,

which is to have a capacity of around 20,000,000 pounds per year.

Another solvent-resisting rubber substitute which was developed at

about the same time that neoprene was developed is made from ethylene

dichloride and sodium tetrasulfide. The ethylene is obtained from

petroleum refinery gases, and the chlorine and sodium tetrasulfide

come from salt and sulfur. This rubber substitute is called "Thiokol."

It was discovered by J. C. Patrick in 1920 in connection with a research

for a cheaper antifreeze solution. In 1938 the consumption of

"Thiokol" exceeded one million pounds.

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