MIL-PRF-87260B(USAF)
and then air dried at 160 ±5°F for a minimum of 30 minutes prior to any preconditioning for
resistivity evaluations. The resistivity specimens shall then be tested (following preconditioning)
in accordance with 4.5.22. Water used in the containers shall be maintained and changed on a
weekly basis. All values for original and final electrical resistivity shall be reported along with
the test conditions (temperature/percent relative humidity) that the specimens were exposed to
during the resistivity measurements.
4.5.17.2 Water immersion.
Tension specimens shall be immersed in pure distilled water at 160 ±5°F for 12 weeks or until
failure.
4.5.17.2.1 Testing frequency.
Testing frequency and water changes shall be at 4-week intervals. Three specimens shall be
tested for each sampling frequency. Testing shall be conducted in loosely capped jars using
900 ±25 ml of water for each of the nine tension specimens. Water used in the containers shall
be changed on a weekly basis.
4.5.17.3 Dry heat.
Tension and electrical resistivity specimens shall be exposed to dry heat at 250 ±5°F for 8
weeks or until failure.
4.5.17.3.1 Testing frequency.
The testing frequency shall be at 2-week intervals. A minimum of three tension specimens shall
be tested for each sampling frequency. Additional specimens shall be exposed for electrical
resistivity evaluations. The specimens shall be in accordance with 4.5.4 and shall be tested, as
a minimum, on a weekly basis. Prior to the start of the test, the electrical resistivity specimens
shall be tested and the test conditions recorded per 4.5.22. All test data shall be reported
including test conditions (temperature/relative humidity) for the electrical resistivity evaluations.
4.5.17.4 Data requirements.
as well as percent loss in tensile strength. In addition, the tensile strength and electrical
resistivity values shall be plotted as a function of exposure time.
4.5.18 Explosion suppression and flame arrestor characteristics.
The explosion suppression and flame arrestor characteristics of the material shall be defined
using a small scale flame tube type apparatus having a minimum total volume of 5 cubic feet
and a 100 square inch cross-sectional area. The following parameters shall be satisfied in all
the testing:
a. Stoichiometric propane/air mixture (4.5 to 5.2 volume percent propane) verified by
bomb sampling
b.
Spark ignition source having a minimum of 0.25 millijoules energy
c.
Dry arrestor material
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