Evening star., 1950-10-02
New Rubber Remains
Elastic in Heat, Cold
Silicon and Oxygen Used
To Replace Some Carbon
By Thomos R. Henry

A type Of rubber which retains all its
rubbery qualities through temperature
range of 223 degrees centigrade is being
tested at the U. s. Bureau Of Standards.
It continues elastic and resistant to
electricity at 100 degrees centigrade above
zero and at 1913 degrees below, the Bu-
reau tests show. Its resistance to low
temperatures makes it of great value for
Arctic and Antarctic air operations. Tires
and betting made of ordinary rubber,
either natural or synthetic, lose their
elasticity and become brittle at about SO
below. .4@
The new rubber, tested by the Bureau
for the Office of Naval Research and the
Quartermaster Corps of the Army, Is
synthetic from which some Of the car
bon atoms have been removed and re-
placed by atoms Of oxygen and silicon. It
was expected that this would bring about
an improvement In cold resistance. That
the treatment also would improve heat
resistance was somewhat unexpected, the
Bureau scientists say.
Ordinary rubber is an amorphous ma
terial with some of the properties OF
solid and some approaching those OF a
liquid. However, previous tests have
shown, at about SO below it changes quite
suddenly into a complete solid. 1t has
no more elasticity than a stone or block
Of ice.
Silicon Better for Cold.
All the silicon rubbers tested were COM
mercial products, designed for conditions
Of extreme cold. Most Of them stood up
well down to temperatures Of rs below.
All but two. however underwent certain
changes at this point-although not as
great as those that take place in natural
rubber-which might lessen their use
fulness. Two samples. however. showed
no changes until the crucial point Of 123
below was reached.
The Bureau tests showed that little
change is caused by the use of yulcanizing
and filling materials in the new rubbers.
Several of these rubbers retain their
properties in temperatures up to 200
above centigrade, making them especially
useful for hose and gaskets in airplane
engines and for insulated cables.
X
The enormous radiation Of an atomic
bomb explosion produces essentially the
same kinds of hereditary changes as
bombarding seeds with X-rays.
This is the conclusion from tests OF
oat, barley, wheat and cotton seeds
exposed to atomic radiation at Bikini.
Although various defornities were noted
in plants grown from these seeds. they
were not different in kind or in fire.
quency from those produced by X-ra-
diation in the laboratory. This despite
the fact that the radiation received was
more than 80 times that which would
be fatal to a man.
Hereditary Changes Studied.
Such is the substance of a report re-
ceived by the American Genetic Asso-
citation from Dr. Luther Smith of the
State College of Washington and DR..
Meta S. Brown of Texas Agricultural
and Mechanical College. Study of the
plants grown from the irradiated seeds
was carried on at various State agri-
cultural stations in a cooperative re-
search project of the Department of
Agriculture and the Office of Naval Re
search. It had been hoped that evi-
dence would be obtained Of specific
hereditary changes which could be
brought about by the intense gamma
radiation and by no other means. This
apparently is not the case.
In the cotton plants, however, there
was notable breaking UP of the chro-
mosomes-bundles of genes, the units of
heredity-in the germ cells. There was
a consequent appearance of dwarf plants.
Many of the plant embryos in the dor
mant seeds were killed and others SO
seriously injured that there was NO
Sprouting.
AS was expected, most of the changes
produced were deadly, so that the plants
literally could not be born. The san1s
Is true after X-radiation.