MIL-DTL-24293B
4.3 Tests. Tests shall be conducted in accordance with the following methods as specified
in FED-STD-311 and as hereinafter specified:
Test
Method
6221
Moisture
Grease (petroleum ether boiling below 176F
(80C)
6311
6515
Chromic oxide, perchloric acid
6351
Soluble chlorides (on grease and wax-free sample)
6361
Soluble sulfates (on grease and wax-free sample)
6421
Total ash
2021
Tensile strength
2021
Elongation (at a stress of 2,500psi (17.24 MPa))
4011
Cracking, vise
1011.1
Thickness, unit
4.3.1 Impregnating wax (benzol extract). After completing the petroleum ether extraction the
same packing and extract with benzol shall be used, using a Soxhlet extractor and keeping the
benzol extraction separate from the petroleum ether extraction. The benzol shall be evaporated
off and dried to approximately constant weight. This extraction shall be used for the melting point
of the impregnating material.
4.3.2 Shrinkage. The length and width of the specimen shall be measured to the nearest .02
inch (.508 mm) along the center lines of the specimen. The specimen shall be immersed in water
at a temperature of 68 to 86 F (20 to 30C) for 24 hours and then heated to boiling at the rate of
17 to 21.5F (5 to 7°C) per minute and boiled for 6 minutes. The specimen shall be removed and
the length and width again measured immediately. The shrinkage shall be computed as
percentage of the original area.
4.3.3 Porosity. A circular porosity specimen, 3 inch (76.2 mm) in diameter made from each
sample marked "A" shall support a head of 1 ft (304.8 mm) of water for 30 hours without showing
porosity. For type II packing, Stoddard solvent shall be used in place of Water.
4.3.4 Chloroform extract. Approximately 10 grams of type II packing shall be extracted with
chloroform using method 6311 of FED-STD-311.
4.3.5 Total polysulfide polymer. Total polysulfide polymer shall be determined as follows.
Accurately weigh 0.25 to 0.30 gram of impregnated packing and place in a Parr Bomb cup. Add
approximately 0.50 gram of benzoic acid, 0.2 gram of potassium perchlorate and enough sodium
peroxide to make the cup two-thirds full. Intimately mix the contents and ignite the bomb. When
cool, dissolve the bomb contents in distilled water, filter, neutralize to methyl orange with
hydrochloric acid then add a few drops in excess, bring solution to a boil and add 10 ml of 10
percent barium chloride with constant stirring. Let the solution stand for at least 16 hours and
then filter. Wash the precipitate free of chlorides, then transfer the filter paper and precipitate to a
tared crucible. Ignite to constant weight. The weight of barium sulfate is converted to percent
sulfur by multiplying by 0.1373, dividing by the same weight and multiplying by 100. Repeat the
determination on a representative sample of unimpregnated packing. Complete the percent of
total polysulfide polymer content by subtracting the sulfur content of the unimpregnated sample
from that of the impregnated and multiplying the difference by 2.74. (This factor is obtained by
dividing 1/0.365 where 36.5 percent is representative of the sulfur content of the polysulfide
polymer.)
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