MIL-DTL-25421C
4.5.1 Standard conditions. Standard conditions shall be 23° ± 1.1° C (73.4° ±
2° F) and 50 ± 4 percent relative humidity. Specimens shall be tested at standard
conditions after being conditioned for 96 hours at this temperature and humidity.
4.5.2 Wet conditions (for mechanical tests). Wet conditioning shall be a two-
hour immersion of the specimen in boiling distilled water. The specimens shall be
cooled in distilled water to 23° ± 1.1° C (73.4° ± 2° F) and shall be tested wet at that
temperature immediately after removal from the water. In case of any questions as
to the validity of the test results, wet conditioning shall be 30 days soaking in distilled
water at room temperature, and the specimens shall be tested wet immediately after
removal from the water. Results obtained under the latter conditions shall be final.
Surface moisture may be wiped from all wet specimens before testing.
4.5.3 Immersion conditions (for electrical tests). The specimens shall be
immersed in distilled water at 23° ± 1.1° C (73.4° ± 2° F) for 24 hours. The specimen
shall then be removed from the water, the surface moisture shall be wiped off, and
the tests shall be conducted immediately at 23° ± 1.1° C (73.4° ± 2° F).
4.5.4 Elevated temperature conditions, 70° C. The specimens shall be
exposed for 30 ± 5 minutes at a temperature of 70° ± 1.1° C (158° ± 2° F) in a test
chamber previously heated to that temperature and shall be tested immediately at the
same temperature.
4.5.5 Elevated temperature conditions 260° C, (Type II only). In the ½ hour
exposure, the specimens shall be exposed for 30 ± 5 minutes at a temperature of
260° ± 2.8° C (500° ± 5° F) in a test chamber previously heated to that temperature
and shall be tested immediately at the same temperature. In the 192 hour exposure,
the specimens shall be exposed for 30 ± 5 minutes at a temperature of 260° ± 2.8° C
(500° ± 5° F) for 192 hours in a circulating air oven. The specimens shall then be
transferred to a previously heated 260° ± 2.8° C (500° ± 5° F) test chamber for an
additional half hour, and shall be tested at that temperature.
4.6 Test methods. Tests shall be conducted by the methods of ASTM D2240
prescribed in Table VI, except as follows.
4.6.1 Barcol hardness. Barcol hardness shall be determined by direct reading
on a Barcol tester. Barcol tester model GYZJ 934-1 shall be used (6.4).
4.6.2 Electrical properties of Class 3 laminate. Electrical properties tests at
8,500 to 10,000 megacycles per second (Class 3 laminate only) shall be performed
by the shunted line wave-guide method or resonant cavity technique (6.3.2), using
the sample specified for that purpose in 4.4.3 and 4.4.3.1. If calculations (6.3)
establish that specimens thinner than the samples furnished would be preferable, the
testing activity is permitted to abrade or otherwise mill the specimens to the optimum
thickness.
14
For Parts Inquires call Parts Hangar, Inc (727) 493-0744
© Copyright 2015 Integrated Publishing, Inc.
A Service Disabled Veteran Owned Small Business