FED-STD-228A
3.2.13.2 Test paper. The solution shall be prepared by dissolving 3 grams of p-dimethylamine
benzaldehyde and 0.05 gram of hydroquinone in 100 ml. of ethyl ether. Filter papers shall be
impregnated in this solution, dried, and cut into strips. The papers shall be stored in a brown glass bottle.
Papers stored under such conditions are stable for several months, but lose their efficiency if stored in the
light. To conduct the test for natural rubber and styrene polymer these papers shall be moistened with
the wetting solution described in 3.2.13.1.
3.2.14 Zinc, granulated.
4. PROCEDURE
4.1 Pyrolysis tests. A specimen containing about 0.5 gram of the rubber compound, free from adhering
fabrics or other material, shall be transferred to the distillation tube of the distillation apparatus 3.1.3 and a
condenser tube attached. The distillation tube shall be fastened in position by means of a clamp and then
heated with a very low flame until the specimen begins to decompose. When vapor appears in the tube,
the end of the condenser tube shall be immersed in 1.5 ml. of solution No. 2, contained in a test tube, and
the distillation continued until it has been determined whether a color change will develop. The
condenser tube shall then be removed from solution No. 2 and transferred to a second receiving tube
containing 1.5 ml. of solution No. 1, and the distillation continued for a few minutes. The distillate in the
two receiving tubes shall be cooled and shaken. The tube containing solution No. 1 shall be examined to
determine whether the drops of distillate sink or float on solution No. 1. Both solutions No. 1 and No. 2
shall be observed for any color change. Solution No. 1 shall be transferred to a 16 by 150 mm. test tube,
5 ml. of absolute methyl alcohol added, the mixture heated on water bath at 100°C (212°F) for 3 minutes,
and any color that develops recorded. All observations made on both solutions shall be recorded and the
material classified by means of table I.
TABLE I
Solution No. 1
Solution No. 2
Material
Initial color
Color after heating
Color
Blank
Pale yellow
Pale yellow
Green
Polyvinyl chloride
Yellow
Yellow
Red
Chloroprene
Do.
Pale yellow green
Do.
Nitrile
Orange red
Red
Green
Chloroprene-nitrile
Do.
Do.
Yellow to red
Styrene
Yellow green
Green
Green
Natural rubber
Brown
Violet blue
Do.
50 styrene-50 rubber
Olive green
Green blue
Do.
Polyisobutylene
Yellow (droplet floats)
Pale blue green
Do.
Polyvinyl acetate
Yellow
Pale yellow green
Yellow
4.2 Spot tests.
4.2.1 Chloroprene-nitrile spot test. A heating element such as a knife, file, or iron shall be heated, either
electrically or by means of a gas flame, to a temperature sufficient to produce dense flames but not high
enough to ignite the rubber specimen. The rubber specimen shall be pressed against the heating
element until fumes are liberated. A strip of the chloroprene-nitrile test paper shall be moistened with the
benzidine hydrochloride-hydroquinone wetting solution and then held in a parallel position about 5 mm.
above the surface of the heating unit, which is pressed against the rubber specimen until a good color is
produced on the side of the paper facing the fumes without scorching the paper of the impregnating
materials.
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