MIL-DTL-27500H
diameter of the mandrel after coating is still in conformity with table IX. This specimen so prepared on the mandrel shall be placed
in an air-circulating oven and maintained for 6 hours at 2000 C ± 50 C for 08 and 58 jackets and 3000 C ± 50 C for 23 and 73
jackets.. After completion of the air oven exposure, the specimen shall be allowed to cool to between 200 C and 250 C (680 F to 770
F). When cooled, the wire shall be freed from tension, removed from the mandrel, and straightened. The specimen shall then be
subjected to the bend test (4.3.6), followed by voltage withstand test procedure of 4.3.7.
4.3.12 Bend test. In a temperature maintained between 200 C and 250 C (680 F to 770 F), one end of the specimen shall be
secured to the mandrel and the other end to the load weight specified in 4.3.11. The mandrel shall be rotated until the full length of
the specimen is wrapped around the mandrel and is under the specified tension with adjoining coils in contact. The mandrel shall
then be rotated in reverse direction until the full length of the cable which was outside during the first wrapped is now next to the
mandrel. This procedure shall be repeated until two bends in each direction have been formed in the same section of the cable. The
outer surface of the cable shall then be observed for cracking of the insulation.
4.3.13 Jacket wall thickness. Specimens of finished cable with jacket material listed in table V shall be measured for wall
thickness of jacket in accordance with MIL-STD-2223, method 6003.
4.3.13 .1 Jacket tensile strength and elongation. Jacket materials requiring tensile strength and elongation testing (see 3.7.5.1)
shall be tested in accordance with ASTM D3032, using 1-inch bench marks, a 1-inch initial jaw separation, and a jaw separation
speed of 2-inch per minute.
4.3.14 Lamination sealing (polyimide/fluorinated ethylene propylene single and double jackets only, jacket materials 11, 12, 22,
61, 62, 72). Specimens shall be tested in accordance with MIL-STD-2223, method 4006, except the heat exposure shall be for 6
hours at 2300 C ± 50 C. . The jacket shall be visually inspected for delamination. Any separation of layers either along the
insulation or at the ends shall constitute failure.
4.3.15 Jacket blocking. One end of the continuous length of finished cable shall be fixed to a mandrel. The cable shall then be
spirally wound around the mandrel so that at least three turns are in close contact with one another. The winding shall be continued
until there are three layers of turns with each layer in close contact with one another. One end of previously untested samples of
finished cable shall be secured to a mandrel. The other end of each specimen shall be secured to separate load weights sufficient to
keep the cable vertical and tangent to the mandrel during the bending operation. The mandrel size shall be as specified in table IX.
The mandrel and cable shall then be placed within an air oven at the specified temperature for the specified time period (see 3.3.7).
After removal from the oven, the mandrel and cable shall be cooled to room temperature and the cable shall be unwound. There
shall be no adhesion or sticking of adjacent turns or layers during the unwinding process.
4.3.16 Concentricity. The concentricity of extruded cable jackets only, shall be tested in accordance with MIL-STD-2223,
method 6003, paragraph 4.2.2.
4.3.17 Cable jacket removability. The cable jacket shall be severed circumferentially 4 inches from the cable end. The cable
shall be flexed at the point of severance to ensure that the jacket is parted completely. The 4-inch slug of jacket material shall be
removed by pulling or working off the cable with the fingers. Finger gripping aids may be used. For jacket styles 11, 12, 22, 61, 62,
and 72 only, stripping time shall start when the jacket slug is gripped for removal after severance and shall end when the jacket slug
has been completely removed from the cable.
4.3.17.1 PTFE tape wrapped jacket delamination. The contrahelically wrapped PTFE jackets, styles 06 and 56, shall be
visually examined for signs of delamination. No instruments or tools shall be used to induce separation of the tape layers.
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