MIL-DTL-38359E
3.3.2 Insulation. The insulation shall consist of a black cross-linked thermoplastic polyethylene (XLP)
compound which meets the requirements for the insulation specified in NEMA WC 71 and all the
requirements specified herein. The insulation shall be applied tightly and concentrically about the
conductor over the conductor shield and shall be free from pores, splinters, and other such defects.
3.3.2.1 Insulation thickness. The average thickness of the insulation shall be not less than that
specified in table I. The minimum thickness at any point shall be not less than 90 percent of the thickness
specified in table I. If the insulation is applied in more than one layer, the adjacent layers shall be molded
into a homogeneous mass and the mass considered as a whole for all measurements and tests.
3.3.2.2 Insulation resistance. The measured insulation resistance (see 4.6.4 ) at 15.6 ºC shall be not
less than that calculated from the following formula:
R = K log10 D
d
Where
R = Megohms - 1000 feet
D = Outside diameter of insulation in inches
d = Diameter of uninsulated conductor in inches
K = Constant 25,000 for insulation specified herein
NOTE: If the temperature differs from 15.6 ºC during the resistance measurement, correction shall be
made by multiplying the calculated value of R by the coefficient corresponding to the temperatures during
measurement. The coefficient for the insulation shall be that specified by the manufacturer. The
temperature coefficient shall be determined in accordance with NEMA WC 71.
3.3.2.3 Joints. All joints made in the insulation shall be such that all parts affected in the process will
be electrically and physically equal to the remainder of the insulation and shall conform to the thickness
requirements specified herein.
3.3.2.4 Physical properties. The physical properties of the insulation shall be as follows:
a. Original physical requirements:
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(1) Tensile strength, initial, 1,800 lbf/in minimum.
(2) Elongation at rupture, 350 percent minimum.
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(3) Modulus at 200 percent elongation, 1,000 lbf/in minimum.
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