MIL-DTL-55668D
3.5 Shield. Shielding shall be served tinsel strands. The ribbon comprising the strands shall be silver or
tin-coated cadmium-copper of .0095 inch (.241 mm) nominal width and .0009 inch (.023 mm) nominal
thickness. A strand shall consist of a single ribbon, spiral-wrapped 54 turns per inch, nominal, around a
cotton thread, or a polyaryl-amide thread conforming to MIL-C-572, type PAA. The shield shall consist of
10 tinsel strands laid adjacent to each other, and spiral-wrapped around the insulated conductor in an
even, helical, right-hand lay, with a minimum of 60 turns per foot. At no cross-section should there be
less than eight strands in a turn. Shield coverage shall be 80 percent minimum, as calculated in 4.7.5.
An overlapping spiral-wrap of .0005 inch (.013 mm) nominal thickness polyester tape in accordance with
MIL-I-631, type G, shall be applied in a right-hand lay over the shield. Another tape may be placed
between the insulation and the shield. The diameter of the taped, shielded insulated wire shall be
approximately .052 inch (1.32 mm).
3.5.1 Shield resistance. The dc resistance of a shield strand prior to application on the insulated
conductor shall be 2.50 per foot maximum, measured at, or corrected to, 20 C (see 6.3).
3.6 Jacket. The jacket shall be a smooth, dense, uniform black elastomer free of surface irregularities.
Jacket dimensions shall be as specified in table . The wall thickness shall be measured on the straight
ends. The jacket material shall be a black vulcanized rubber compound based on one of the following:
a. Styrene butadiene rubber (SBR) or blend of SBR and polyisoprene rubber, not exceeding 35
percent natural or synthetic polyisoprene by weight.
b. A blend of SBR and ethylene-propylene terpolymer (EPDM), with 25 percent EPDM by
weight, minimum.
c.
EPM rubber or EPDM rubber.
3.6.1 Jacket material properties. Vulcanized rubber jacket materials shall meet the requirements of
jacketing compound, type JS-L low temperature, heat resistant, styrene butadiene rubber, except as
specified in table II. The actual values shall be recorded and forwarded with first article sample test data
(see 3.1). Unless otherwise indicated, specimens shall be taken from the straight section of finished
cord; for first article inspection testing, cords may be made up with extra-long straight sections.
3.6.2 Anti-deterioration agents. The rubber compound shall contain anti-oxidants, anti-ozonants, and
sunproofing waxes of the types and amounts necessary to provide long-term protection, yet not interfere
with adhesion to subsequent rubber strain-reliefs, seals, or crotch-splices.
3.7 Cord construction.
Cord construction parameters. The core shall consist of a staycord in the center around which
3.7.1
the insulated conductors and fillers are twisted in a right-hand lay. Powdered soapstone
(lubricant) shall be applied to the completed core just prior to jacketing the cord. For a retractile
cord, the helical portion shall have a left-hand lay with adjacent turns contiguous and a straight
length of cord at each end tangent to the coil. The cord construction parameters consisting of the
number of conductors, number of shielded conductors, core diameter, core lay, jacket wall
thickness, jacket diameter, and, for retractile cords, the helix outside diameter shall be specified
in table I.
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