MIL-DTL-28693A
c. The swelling in testing fuel of the friction rubber shall be determined using specimens cut
from the sample obtained in accordance with 4.5.3.4.
4.7.9.1 Initial tensile properties (see 3.4.2.1). Hose samples shall be tested for initial tensile
strength and ultimate elongation in accordance with ASTM D412, test procedure A, using specimens cut
with die C (dumbbell).
4.7.9.2 Tensile properties after immersion (see 3.4.2.2). Hose samples shall be tested for tensile
strength and ultimate elongation, after immersion in ASTM reference fuel B for 46 ±1/2 hours at 73°F
±4ºF (22.8° ±2.2°C), shall be determined in accordance with ASTM D471, using specimens cut with die
C (dumbbell) as specified in ASTM D412. Tensile strength shall be based on the swollen cross sectional
area of the specimen.
4.7.9.3 Tensile properties after oven aging (see 3.4.2.3) Hose samples shall be tested for tensile
strength and ultimate elongation after oven aging shall be determined in accordance with ASTM D573,
using specimens cut with die C (dumbbell) as specified in ASTM D412, except that the aging period shall
be 70 ±1/4 hours at 212°F ±2º F (100°C±1.1°C).
4.7.9.4 Volume change after immersion (see 3.4.2.4). The change in volume of samples of the
tube, cover, and friction rubber after immersion in ASTM Reference Fuel B for 46 ±1/2 hours at 73°F
±4ºF (22.8° ±2.2°C) shall be determined in accordance with ASTM D471. The change in volume shall
be reported as a percent of the original volume.
4.7.9.5 Initial adhesion (see 3.4.2.5). The adhesion of the tube and cover to the reinforcement, and
the plies of reinforcement to each other, shall be determined in accordance with ASTM D413 machine
method, and shall meet the requirement of 3.4.2.5.
4.7.9.5.1 Specimens. Strip or ring specimens shall be prepared in accordance with ASTM D380.
For determining adhesion between plies of reinforcement, the plies to be separated must be at opposing
angles. Three specimens of each interface shall be tested.
4.7.9.6 Adhesion after immersion (see 3.4.2.6). The adhesion of the tube and cover to the
reinforcement, and of the plies of reinforcement to each other, shall be determined after the test
specimens (see 4.5.3.2) have been immersed in ASTM reference fuel B in accordance with
ASTM D471 for 46 ±1/2 hours at 80°F ±9ºF (26.7°C ± 5°C). The procedure for adhesion shall be in
accordance with ASTM D413 machine method, except the wet specimen shall be tested within 15
minutes after it is removed from the fluid. The adhesion values shall meet the requirement of 3.4.2.
4.7.9.7 Nonvolatile extractable material (see 3.4.2.7). Test samples when tested for nonvolatile
extractable material shall meet the requirements of 3.4.2.7. The test shall be performed in duplicate and
results averaged. The following details shall apply
a. Each specimen shall consist of strips about 1/16-inch square by 2 inches long, totaling about
5 grams in weight, cut from buffed pieces of the tube of the hose.
b. The specimens shall be weighed and placed in an extraction thimble in the extraction
apparatus in accordance with ASTM D297.
c. 100 ml (milliliters) of ASTM reference fuel A in accordance with ASTM D471 shall be added
to the flask.
d. The specimen shall be extracted for 46 ±1/2 hours at such a rate that 2-1/2 to 3-1/2 minutes
are required to fill the empty extraction cup.
e. The extract shall be poured into a weighed container.
f. The specimen and flask shall be rinsed with 25 ml; of fresh reference fuel A and the wash
added to the extract.
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