Man's physical universe

xanabras

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710 CREATIVE CHEMISTRY

need not be extensible.

Natural rubber suffers from several disadvantages.

It swells on contact with organic liquids such as petroleum

products (gasoline, lubricating oils, etc.) ; it is not resistant to oxidation

by the oxygen of the air.

The original synthetic rubber, a polymer of dimethylbutadiene,

developed by Germany during World War I, was a poor substitute

for natural rubber, but it

has been greatly improved

by building large molecules

from a mixture of butadiene

and other unsaturated

compounds. Thus Buna S

tires on which the German

mechanized army rode

in 1940-1941 were made

by polymerizing butadiene

with styrene.

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Fig. 304. The Firestone B-iy bomber tire.

(Courtesy of the Firestone Tire and Rubber

Company.)

I

C

// \

HC C—CH=CH2

HC C—

\ / C

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This rubber is approximately

equal to natural

rubber in its resistance to

abrasion and heat.

Buna N, more commonly

referred to as Perbunan, is

another copolymer of butadiene, which is particularly desirable because

of its resistance to swelling with liquid hydrocarbons. Buna N is made

by polymerizing butadiene with acrylonitrile, CH2=CH—C^N. Tires

made from Perbunan may wear slightly longer than tires made from

natural rubber. In 1940 the Standard Oil Company, a corporation of

New Jersey, made public its plans to erect a Buna plant having a

capacity of 10,000 pounds per day under the patent rights originating

with German chemists and now owned by one of Standard's United

States subsidiaries. This plant went into operation in 1941 at the

refinery of the Standard Oil Company of Louisiana in Baton Rouge.

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