Evening star. [volume] (Washington, D.C.) 1854-1972, 1929-11-10
SUN SUBSTITUTE
NEED FOR RUBBER
Chemists Develop Various
Means of Imparting En-
durance to Products.

To find a substitute for the sun is
the task confronting the rubber indus
try in a quest to prolong the life of
rubber products, J. M Bierer and c. G.
Davis, industrialists, of Cambridge,
Mass, declare in a symposium on the
aging of rubber conducted by the divi-
sion of rubber chemistry of the Ameri-
can Chemical Society
The main hazards to which rubber
goods are exposed, according to Bierer
and Davis, are oxidation, heat effects,
mechanical work and sunlight. Tests
approximating the effect of these fac
tors, except the sunlight. they say, have
been developed to high degree OF
practical utility. A practical test to
duplicate the effect of the sun on such
products as auto topping and bathing
caps. however, is yet to be perfected.
THE more varied the uses to which
rubber is put explains Bierer, the
more varied are the conditions under
which it ages, and the less it can be
expected that any single aging test
will duplicate these various conditions.
The most important factors which pro- /
mote the deterioration Of rubber goods
are oxidation by atmospheric oxygen,
decentralization, heat effects, crack
ing and other changes from exposure to
sunlight, and wear or deterioration due
to mechanical work.
Exposure Of Types Differ.
mo two types of rubber products are
exposed in just the same way to these
various influences. One product may
be exposed to a marked degree to only
one Of the influences, whereas another
may deteriorate from all five influences.
Thus, automobile tires undergo oxida-
ton, -vulcanization, heat effects,
cracking from exposure to sunlight anu
abrasion and deterioration from me-
chanical work. On the other hand
steam hose deteriorates predominantly
from INFLAMMATION and heat eff
fects, oxidation, mechanical work and
sunlight playing almost no part"
Since every kind of rubber article is
exposed to different dangers, Bierer
points out, an attempt to duplicate in
the laboratory the different combina-
tons of hazards involved would neces-
state different test for every type of
rubber goods manufactured. This. he
adds, is impractical and undesirable
The artificial aging tests which have
developed up to the present time have
been based on an entirely opposite |
principle, Davis reports. Chemists of
the large rubber manufacturers have |
tried only to determine the resistance |
of rubber product to the one most i'm
portant influence to which 1t is ex-
posed in service. The Geer oven test, |
which Is heat test: the oxygen bomb |
test developed by Pierer and Davis, |
wherein rubber is suspended in oxygen |
at certain temperatures to approximate |
the effects of oxidation: the Fadeo- |
meter test, which is an effort to simu- |
late the effect OF the sun, and various |
mechanical tests are all based on this |
principle.
Intensifying of Sunlight.
"Thus, when bathing caps are ex-
posed to . Fadeometer or to ultra-vio-
is only to intensity greatly the action |
of sunlight, while oxidation, after-vul- |
canization and other effects are ignored. |
Similarly when inner tubes are aged in !
the oxygen bomb, the purpose is to de-
termine their resistance to oxidation |
and to regard the influence Of heat and
mechanical work.
Because most rubber goods deterio-
rate from several influences rather than |
one, and because preSent-day aging tests /
do not intensity each Of the factors to |
the same degree, it cannot be expected |
that any OF the aging tests duplicates |
natural aging. Nevertheless, where the |
predominant effect in the artificial test |
is also the predominant effect in nat |
ural aging, almost the same results !
from practical viewpoint are obtained. |
Tests which intensity oxidation, heat |
effects and mechanical work have been |
developed to high degree Of practical |
utility, but 1t still remains for someone |
to develop test for Stimulating the eff |
fects of sunlight. The Fadeometer and
ultraviolet light tests represent at
tempts to duplicate the effects of sun
light, but evidence thus far shows that
these tests do not duplicate the effects
of the sun and only give misleading re-
suits There Is, accordingly, an urgent
need for an aging test that will approx
innate the effects of sunlight"
The oxygen bomb, perfected by Bic
rer and Davis. is the most recent test
developed by the industry in its fight
against the effects of oxidation. 1t has
supplanted in many cases the classical
Geer oven test. The oxygen bomb Is
largely responsible for the ability of
inner tube manufacturers to build a
tube which remains in good condition
after 10000 miles.
The value of the bomb, however, rests
entirely in foreseeing the natural aging
of rubber products which deteriorate
chiefly from oxidation. Rubber experts
are agreed that until tests other than
those involving oxidation in darkness
are developed the rubber industry will
remain without any means of foreseeing
the natural aging of some Of Its most
important products.