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|  MIL-S-27332B(USAF)
The ultimate elongation shall be calculated by subtracting the original
distance between bench marks from the total distance between bench marks at
the time of rupture and expressing this difference as a percentage of the
original distance.
4.6.6 Compression set. Three specimens, with dimensions of 1 by 2 by
2 inches, shall be cut from three different seat cushion inserts and tested
to determine. compliance with the requirements of 3.5.5. The entire test
procedure shall be conducted under the following conditions. All gaging, -
o
conditioning, and recovery shall be conducted at 73 +2 F and in an atmos
phere having a relative humidity of 50 + 2 percent. After cutting, the
specimens shall be conditioned for 3 hours and then placed in an apparatus
which will deflect the specimen to 50 + 1 percent of its height. Within
15 minutes after deflection, the deflected specimen shall be placed in a
mechanically convected air oven for a period of 22 hours at a temperature
of 158 +2F and a relative humidity of 5 +1 percent, After removal from
the oven, the specimen shall be removed from the deflecting apparatus and
allowed to recover for 35 +5 minutes. After recovery, the specimen shall
be gaged, and the compression set shall be calculated by expressing the
difference between the original height after removal from the apparatus as
a percentage of the original height.
4.6.7 Air oven aging. Three seat cushion inserts shall be subjected to
an air oven aging test to determine compliance with the requirements of
3.5.6. The inserts shall be placed in a mechanically convected air oven at
a temperature of 212 _2F for not less than 3 hours. Load deflection
+
characteristics shall then be obtained by the procedure described in
4.6.2.1. The same specimens used in the load deflection charecteristics
tests may be used for this test.
4.6.8 Humidity aging. Three specimens, with dimensions of 2 by 2 by 1
inch and cut from three different seat cushion inserts, and three seat
cushion inserts shall be subjected to a humidity aging test to determine
compliance with the requirements of 3.5.7.1 and 3.5.7.2. The specimens
shall be initially dryed for 3 hours at 158 2F in a mechanically con-
vected dry air oven. After drying, the specimens shall be allowed to come
to equilibrium after removal from the oven for at least 2 and no more than
24 hours under ambient temperature and humidity conditions as specified in
4.3.1. The humidity test shall be carried out in an autoclave which has
been filled to a level of 2 inches above the bottom with freshly distilled
water. Both sets of test specimens shall be placed in the autoclave so
they do not touch one another or any metal except the supporting surface.
With the safety valve open, the water in the autoclave shall be brought to
a boil. When all the air is expelled, the safety valve shall be closed and
o
the pressure maintained at 1 to 4 psig (216 to 225 F) for 3 hours. At the
end of this time, the specimens shall be removed and dried for 3 hours at
o
158 + 2 F in a mechanically convected dry air oven. After removal from the
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