FED-STD-228A
Method 7251.1
18 APRIL 2014
IDENTIFICATION, SYNTHETIC ELASTOMERS, INSULATION AND SHEATH
1. SCOPE
1.1 This method is intended for use in identifying natural and synthetic rubbers, and polyvinyl resins
when each is present alone in a compound. It may also be used to identify the component in some
mixtures containing more than one type of rubber. In those cases, especially in mixtures where
ambiguous colors are obtained, it will be necessary to use specimens that have been previously extracted
with acetone.
2. SPECIMEN
2.1 The specimen should consist of at least 10 grams of the insulation or sheath compound taken from
the inspection unit, prepared as described in method 7001.
3. APPARATUS AND REAGENTS
3.1 The apparatus shall be as follows:
3.1.1 Baths; ice, steam.
3.1.2 Copper wire.
3.1.3 Distillation apparatus consisting of a test tube, 10 by 75 mm., equipped with a glass condenser
tube 4 mm. in outside diameter attached to the test tube by means of a cork stopper. The condenser
tube shall be bent at least 90° and shall extent about 100 mm. beyond the bend.
3.1.4 Evaporating dish, 70 ml.
3.1.5 Extraction equipment, Soxhlet or similar type.
3.1.6 Funnel, separatory, 250 ml.
3.1.7 Heating element; electrically or flame heated knife, iron, or file.
3.1.8 Reflux apparatus.
3.1.9 Test tubes 16 by 150 mm. and 10 by 75 mm.
3.2 Reagents. The reagents shall be as follows:
3.2.1 B-naphthol in 5 percent sodium hydroxide solution.
3.2.2 Bromine.
3.2.3 Iodine, 0.02 gram per liter of carbon tetrachloride.
3.2.4 Mercuric acetate, 5 percent in methyl alcohol solution.
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