MIL-PRF-23586F
4.7.9 Brittle point. Molded sheets, approximately 0.075 inch in thickness, shall be cured as
specified in 4.6. The brittle point of the compound shall be determined in accordance with
ASTM-D746.
4.7.10 Adhesion.
4.7.10.1 Preparation of panels. A coating of compound, 0.125 ±0.030 inch thick, shall be
applied to the primed side (as recommended by the manufacturer) of a 3 by 6 by 0.0625 inch
aluminum alloy panel conforming to QQ-A-250/13 (see figure 1). Two strips, measuring 1 inch by
12 inches by 0.006 inch, of a thin flexible material (such as 30 mesh aluminum screen primed when
required, as specified by the manufacturer) shall be placed primed side down on the surface of the
freshly applied compound. The strips shall be placed so that they are 0.25 inch from each edge and
0.5 inch apart, leaving a 6 inch long tail. Four panels shall be prepared and cured as specified in
4.6. Two panels shall be tested upon completion of the curing period. Prior to testing, the
remaining two shall be exposed as specified in 4.7.15.
4.7.10.2 Testing of panels. The panels shall be individually tested in an autographic testing
machine whose capacity shall be such that the tension at failure is not more than 85 percent nor less
than 15 percent of the full scale load. If the machine is of the pendulum type, the weight shall
swing as a free pendulum without engagement of the pawls. The rate of separation of the jaws
shall be 2 inches per minute. Specimens shall be mounted in the machine so that the loose end of
the aluminum mesh strip will be folded 180° as it is pulled from the panel. Each strip shall be pulled
as follows: A cut through the sealant to the panel at the junction of separation shall be made at an
angle of 45 in the direction of separation. If the sealant separates from the aluminum mesh, similar
45 degree cuts shall be made to promote separation of the sealant from the panel. A minimum of 5
cuts shall be made. The adhesion in pounds shall be automatically recorded on a chart as a
continuous curve. The adhesion value shall be calculated by averaging the maximum forces
required to separate the sealant from the panel.
4.7.11 Repairability. A coating of compound, 0.125 inch thick, shall be applied to the primed
(if required) side of each of two 3 by 6 by 0.0625 inch thick aluminum alloy panels conforming to
QQ-A-250/13. Both panels shall be cured as specified in 4.6. One panel shall be oven aged at
240° ±3°C (400° ±5°F) for 72 ±2 hours. The surface of specimens cured in accordance with 4.6.2
shall be lightly abraded before recoating. Each coated panel shall then be recoated with an
additional 0.125-inch thickness of freshly mixed compound. Aluminum strips shall be placed as
specified in 4.7.10, with testing as specified in 4.7.10.2.
4.7.12 Hydrolytic stability, physical.
4.7.12.1 Specimen preparation. Sufficient base compound and curing agent shall be mixed to
prepare 3 molded test specimens, 2½ inches in diameter by ½-inch thick. After a 3-second
application time, hardness shall be determined using a type A Durometer in accordance with
ASTM-D2240. Hardness shall be determined at the same locations before and after exposure.
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