Chemistry in the Industries 293
isobutylene. This is polymerized with some butadiene or iso-
prene resulting in a product called Butyl rubber. Butyl rub-
ber is not as good a synthetic rubber for tire use as the
Buna-S. The last type, and the one looked to at present as
the most satisfactory, is “Buna” rubber. The two best known
Buna compounds are Buna-N and Buna-S. Buna-N is the
result ofbuilding up butadiene and acrylonitrile; and Buna-S
is butadiene with styrene. Compared to natural rubber,
Buna-S is poorer in tear resistance, heat build-up, and flex-
ing, but superior in aging and resistance to abrasive wear.
Since styrene is now readily made from coal and oil, the
chief problem of supply is to make the butadiene. The
chemist has a choice of processes—to make butadiene from
petroleum products, from starch (grain or potato), or from
acetylene. Russia elects potato starch as her basic raw ma-
terial, converting it into alcohol and by a catalytic process,
converting the alcohol into butadiene. Our chemists have
greatly improved the Russian process, and there was power-
ful pressure from farm interests to make this the official
method. Claims of quicker production, lower costs, and the
use of less critical metals in construction, filled the air with
controversy. However, the oil companies began their work
earlier, and have contracts. On January 30th there was an
announcement that the new Standard Oil Company plant
in Louisiana had started production of butadiene with an
estimated output of 9,000 tons per year. Many other plants
have been producing butadiene in large quantities.
Certain special uses of synthetic rubber are new. When you
read of a badly shot-up American plane returning safely to
its base, the chances are that Butyl rubber deserves a share
of the credit. That is because all American battle planes
being built today have gasoline tanks protected by a bullet-
sealing lining of soft gum insulated by a gasoline-resistant