MIL-R-83248C
4.6.3 Oil aging test. Oil aging of specimens shall be conducted in accordance with ASTM D 471 and ASTM D 1414. Do not dip specimens in acetone, blot dry residual oil from specimens.
4.6.3.1 Oil aging time and temperature. The oil-aging time and temperature shall be 70 hours at 392°F ± 5°F. After aging and prior to the physical property determinations, the specimens shall be removed from the hot fluid and cooled
30 minutes in fresh fluid. Tensile strength, elongation, hardness, and volume change shall then be determined as specified in 4.6.1.
4.6.4 Fuel aging test. Specimens shall be immersed in test fluid conforming to ASTM Reference Fluid B (ASTM D471), for 70 hours at 75°F ± 5°F. The ratio of fluid to rubber shall be approximately 40 ml per gram. Aging shall be conducted in a glass container. An airtight seal shall be maintained for the duration of the test. One sample at a time shall be removed from the fluid, immediately blotted dry, and tested. The tensile strength, elongation, hardness, and volume change tests shall be conducted in accordance with 4.6.1.
4.6.5 Compression set test. Compression set shall be determined in accordance with ASTM D395, method B. Specimens for type I materials shall be two o-rings. Two circular plied-up buttons with dimensions to 1.129 ± 0.010 inches diameter and approximately 0.5 inch thick shall be used for type II material.
4.6.5.1 Oil aged test for specimen. Compression set shall be determined on specimens aged 70 hours at 392°F ± 5°F
immersed in fluid conforming to ARM 200. The compression set plates for testing type I material shall be approximately
0.375 inch by 2 inches by 4 inches. There shall be six 1/4-inch bolt holes; one on each corner and one located in the middle of each 4-inch edge and on the center line of the corner holes. There shall also be 1/4-inch holes through the middle of each half of the plates to allow fluid to be in contact with the inside diameter of the o-rings. Equivalent fixtures may be used. The compression set plates for type I compression seals other than o-rings and type II material shall be in accordance with ASTM D395. The original thickness of the specimens shall be measured and the test fixtures shall be assembled using two test specimens. The specimens shall be compressed 25 percent. The test fixture shall be placed in a 1-liter stainless steel beaker and 800 milliliters of ARM 200 fluid shall be added to the beaker. The beaker shall be fitted with a suitable vented stainless steel cap. The cap shall be sealed with an o-ring conforming to type 1, class 1 of this specification (size-240, AS 568 has been used). The beaker shall be placed in a suitable oven at 392°F ± 5°F with vent open. After the fluid has reached the test temperature (approximately 2 hours) the vent shall be closed and the beaker left in the oven for a total aging time of 70 hours. At the end of the aging time, the specimens shall be removed from the compression plates immediately and allowed to cool on paper towels for 30 minutes. Excess fluid shall be blotted from the specimens with paper towels and the final thickness determined.
4.6.6 Humidity aged test. Aging shall be conducted in a suitable chamber maintained at 77°F ± 2°F and 95 ± 3 percent relative humidity for 28 days. The specimens shall be tested or subsequent exposures initiated within 30 minutes after
removal from the humidity chamber.
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