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|  MIL-H-46354A(MU)
4.6.5 Accelerated aging.- The aging test shall be performed in a
heating chamber equipped with automatic temperature controls capable of
maintaining the chamber at the operating temperatures specified and shall
be suitably baffled to prevent dead spots and local overheating. The tem-
perature variation throughout the chamber shall not exceed three degrees
Fahrenheit. The heating medium shall be air, thoroughly circulated by
mechanical means at atmospheric pressure. The source of heat shall be lo-
cated in the air supply outside the chamber proper. Provisions shall be
made for the vertical suspension of specimens without contact with each
other or the sides of the chamber. A recording thermometer shall be lo-
cated in the upper central portion of the chamber near the center of the
specimens or headrests. The speciment of headrest shall be placed in the
chamber, after the chamber has been pre-heated to a temperature of 158F
2F, and shall be kept in the chamber at that temperature for a period
of 70 hours. At the end of the 70 hour period, the specimen or headrest
shall be removed from the chamber and subjected to a tactile and visual
examination for tackiness and deformation. The specimen or headrest shall
then be cooled at room temperature (70F 8F) on a flat surface for a
period of at least two hours. The specimen or headrest shall again be sub-
jected to the flexibility test specified in 4.6.3. The force required for
this compression deflection shall not exceed the value specified.
4.6.6 Low temperature flexibility (type I and type II). This test
shall be performed in a cold chamber maintained at the specified low temp-
erature. Subsequent to the oven aging test the specimen or headrest shall
be placed in the cold chamber for a period of 20 to 24 hours. Immediately
following this time cycle, and while the specimens are in the chamber, they
shall be subjected to the flexibility test. The force required for a 25
percent compression deflection shall not exceed the value specified for the
type of construction under test. The device and method of application used
to perform the flexibility test of 4.6.3 shall be used for this test.
4.6.7 Adhesive bond strength.
4.6.7.1 Coating to pad.- The test specimen shall be a sample speci-
men of either Type I or Type II construction, as required, and shall be a
specimen not previously used in other tests. This test shall be performed
using a suitable tensile test device. Two parallel cuts one inch apart
shall be made through the coating and one end of the strip thus formed
shall be cut free and pulled up perpendicular to the specimen surface suf-
ficient to form a gripping tab for the pull test. When pulled to failure
at a rate of five inches per minute the rupture shall occur in either the
pad or the coating and not in the bond (adhesive).
4.6.8 Coating.
4.6.8.1 Tensile strength and elongation.- This test shall be per-
formed in accordance with Method 4111 of FED-STD-601. Sample test pieces
shall be obtained by stripping the coating from the backplanes or pads of
the test specimens used in the adhesive bond strength test of 4.6.7. The
tensile strength and elongation of the coating shall meet the requirements
of 3.9.1.
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