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National Advisory Committee for Aeronautics, Technical Notes - Effect of Aging on Taut Rubber Diaphragms

As part of an investigation of special adipositions
of rubber suitable.for use as diaphragms for'aircraft in-
struments, six samples were used as taut diaphragms in in—
struments and allowed to age for five years. Two of the
instruments were in.operating condition after this period v;+u
of time and one had remarkably little change in perform—
ance. In making the rubber tetramethyl thiuram disulphide
was employed as a vulcanizing agent.

It is recognized that rubber with good aging charac-
teristics would be of value as a material for making dia—
phragms for sensitive pressure indicators, owing to its
large deflections as compared with other materials common-
ly used. Rubber diaphragms which Were used previous to
1924, have performed satisfactorily for a short period of
time, but owing to the rapidity with whidh' the rubber J.o—
teriorated, the instruments required frequent recalibra—
tions and ultimately’became unfit for use in a much short—
er time-than is desirable.

As a contribution toward-solving this problom, the _
Bureau of Standards, with the financial assistance of the _
National Advisory Committee for Aeronautics, investigated ‘
in 1924, the behavior of a number of compositions of rub-
ber containing eacelerators at that time known.’ TheSe
samples Were prepared at the Bureau of Standards by Dr.

The composition of the rubber‘samples_pn which data
were obtained as diaphragms, is given in Table I. The
identification-numhef”of'the instrument in which each dia—
phragm was installed for test is also given in the table.