U\)This specification covers 2, 3, and 4 cadmium copper alloy stranded retractile conductor electrical cords. These cords are insulated with a natural rubber compound encased in a Buna S or Buna S and natural rubber compound jacket which is vulcanized in a helical spring coil form to produce a cord which will extend and retract freely. These cords are designed for use on communications equipment at audio frequencies, with a temperature range of -0 to 60 degrees C for continuous operation.

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MIL-DTL-13273C

insulating, the elongation of individual strands shall be not less than 5%, and the tensile strength shall not

exceed 58,000 psi.

3.4 Insulation. The stranded conductors shall be insulated with a natural rubber compound capable

of meeting the requirements specified herein.

3.4.1 Colors. The color of the insulation on the two conductors of the two conductor cord shall be

black and white, respectively. The color of the insulation on the three conductors of the three conductor

cord shall be black, white and red, respectively. The color of the insulation on the four conductors of the

four conductor cord shall be black, white, red, and green respectively.

3.4.2 Sunproofing wax. The Buna S insulating compound shall contain not less than 2.5 pounds of

approved sunproofing wax per 100 pounds of Buna S in the finished insulating compound.

3.4.3 Dimensions. The diameter of the insulated conductor shall not exceed 0.080 inch (2.03 mm),

and the minimum wall thickness at any point shall be not less than 0.010 inch (.25 mm).

3.4.4 Physical properties. The insulating compound shall conform to the following physical

requirements before and after aging:

Unaged:

Tensile strength, minimum, psi.

600

Elongation, minimum, percent

250

Set, maximum inch

0.5

After 96 hours aging in oxygen bomb at 70� 1�C

Tensile strength, minimum, psi.

450

Elongation, minimum, percent

175

The insulation shall be capable of stripping freely from the conductor. The compound used shall contain

not more that 0.5% of free sulfur after vulcanization.

3.5 Cabling. The insulated conductors shall be cabled together with a right hand lay of twist not

greater than 1.5 inches (38.10 mm).

3.6 Jacket. The cabled conductors shall be jacketed with a smooth dense, Buna S compound or

Buna S, natural rubber blend compound. The amount of natural rubber in the jacket compound shall not

exceed 25% by weight of the total Buna S and natural rubber in the compound. The jacketing compound

shall contain not less than 4 pounds of an approved type of sunproofing wax per 100 pounds of the total

of Buna S and natural rubber in the jacket compound after vulcanization into the construction, the

average diameter of the 2-conductor cord shall be 0.220 inch (5.59 mm) � 0.010 inch (.25 mm), and the

average diameter of the 3 and 4-conductor cordage shall be 0.250 inch (6.35 mm) � .010 inch (.25 mm).

The average diameter shall be taken as the mean of the maximum and minimum diameter in any cross-

section of the straight length of cord. The jacket thickness at any cross-section of cord shall be not less

than 0.010 inch. (.25 mm) The minimum jacket thickness on the straight portion of the cord shall be

0.020 inch (.51 mm). The jacket shall be free stripping from the insulation.

3.6.1 Jacket physical properties. After vulcanization, the jacket shall have the following physical

properties measured on straight portions of the cord.

3.6.1.1 Jacket physical properties before aging. The tensile strength of the jacket shall be not less

than 1200 psi. The jacket elongation shall be not less than 175%.