MIL-PRF-2765E
substitute samples shall be certified to be of the same material and equivalent cure as that used in the lot of
finished material offered for delivery.
4.3.1.4 Rejection. Samples tested as specified in 4.2 and 4.3 which fail to meet the requirements
specified herein shall be cause for rejection. If the failure occurred during first article testing additional samples
shall be taken from each subsequent lot and shall withstand the test wherein the failure occurred. The additional
testing shall be discontinued after four successive lots have passed the test or tests.
4.4 Examination. Each of the samples taken in accordance with 4.3.1.2 shall be subjected to surface
examination for identification markings, workmanship, dimensions, and tolerances. Visual defects shall be
determined and evaluated in accordance with MIL-STD-289, MIL-STD-298, and MIL-STD-407.
4.4.1 Rejection. If the number of defects exceeds the applicable acceptance number shown in Table IV,
this shall be cause for rejection of the entire lot.
4.5 Testing methods. Unless otherwise indicated in the test method, specimens shall be conditioned for
at least 4 hours at room temperature 27 ± 5 degrees Celsius (°C) (80 ± 9 degrees Fahrenheit (°F)) before testing.
Sample preparation may be undertaken without regard to this time interval.
4.5.1 Tensile strength and ultimate elongation. Tensile strength and ultimate elongation shall be
determined in accordance with ASTM D 412 Die C. Specimens, 0.070 to 0.090-inch thickness, shall be used for
determinations of all tensile and elongation properties.
4.5.2 Hardness. The hardness shall be determined in accordance with ASTM D 2240. The instantaneous
reading shall be taken using a durometer, Type A.
4.5.3 Specific gravity. The specific gravity shall be determined in accordance with ASTM D 792.
4.5.4 Delamination test. The delamination test shall be conducted in accordance with ASTM D 471
except that the immersion medium shall be tetrahydrofuran.
4.5.5 Oven aging. Specimens for the tensile strength and ultimate elongation test, hardness test, and hot
compression set test shall be aged in accordance with ASTM D 573 for 46 ± 1/4 hours at 90 ± 1.1°C (194 ± 2°F).
Determination of aged tensile and hardness properties shall be made not less than 20 hours or more than 48 hours
after removal from the oven.
4.5.5.1 Tensile strength and ultimate elongation after oven aging. Tensile strength and ultimate
elongation shall be determined after oven aging in accordance with ASTM D 412.
4.5.5.2 Hardness after oven aging. Hardness shall be determined as specified in 4.5.2 after oven aging.
4.5.5.3 Hot compression set. Hot compression set shall be determined in accordance with ASTM D 395,
method B. The specimens shall be compressed to 40 percent deflection and subjected to the conditions as
specified in 4.5.5.
4.5.6 Oil immersion. Specimens for tensile strength and ultimate elongation test, volume change, and the
cold compression set test shall be conditioned for 94 ± 1/4 hours at 70 ± 1.1°C (158 ± 2°F) in reference oil IRM
903 in accordance with ASTM D 471.
4.5.6.1 Tensile strength and ultimate elongation after oil immersion. Tensile strength and ultimate
elongation shall be determined after oil immersion, in accordance with ASTM D 412. After removing the
specimens from the oil, they shall rest at room temperature no less than 30 minutes or longer than 60 minutes
before testing. The tensile strength shall be based on the swollen cross-sectional area.
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