MIL-DTL-3849C
APPENDIX
A.1. SCOPE
A.1 Scope. This appendix details the test requirements for medium-low temperature styrene-
butadiene rubber (SBR) insulating compounds. This appendix is a mandatory part of the specification.
The information contained herein is intended for compliance.
A.2 SBR Insulating compounds.
A.2.1 Ozone-protective wax. SBR compounds shall incorporate an "ozone protective" wax to protect
the insulation and jacket against cracking due to exposure. SBR insulating compounds shall contain not
less than 4 parts by weight of ozone protective wax per 100 parts by weight of base rubber-polymer when
tested in accordance with ASTM D297.
A.2.2 Free elemental sulfur. Rubber latex and rubber latex-chloroprene rubber latex compounds
shall not contain more than .5 percent free elemental sulfur, natural rubber compounds not more than .1
percent free elemental sulfur, and styrene-butadiene rubber compounds and ethylene-propylene-diene
rubber compounds not more than .25 percent free elemental sulfur.
A.2.3 Free elemental sulfur. Free elemental sulfur content shall be determined in accordance with
method 16211 of FED-STD-601, except that where greater sensitivity is required, a .01 iodine solution
shall be used and the blue end point shall last 3 to 4 seconds.
A.3 Physical properties. Physical property requirements shall be as specified in table A1.
Table A1. Physical property requirements.
Test method
Test
Examination
paragraph
Unaged;
Tensile strength, minimum
1600 psi (110.31 bar)
A.4
Elongation, minimum percent of original
300%
A.5
Set, maximum
.375 inch (9.53 mm)
A.6
After 95 ± ½ hour oxygen bomb aging at 70°C
A.7
75 psi (5.17 bar)
A.4
Tensile strength, minimum
65%
A.5
Elongation, minimum percent of original
Ozone resistance (after air-oven conditioning)
and 168 ± 1 hour in ozone:
A.8
At 38°C
No visible cracks
Brittleness temperature:
A.9
-40°C Max
Unaged
-40°C Max
Aged
A.9.d (1)
Cold tension recovery:
At -40°C
20% minimum
A.10
A.3.1 Condition and age. Specimens shall not be heated, immersed in water, or subjected to any
mechanical or chemical treatment not specified herein. No tests shall be made within 24 hours after
manufacture unless agreed to by the manufacturer.
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