MIL-PRF-23942A(AS)
2.5 percent polybutadiene solution in the sample cell and pure carbon disulfide in the reference
cells. Examine the carbon disulfide absorption bands at 4.35, 4.65 and 11.65 µm (see 6.4.2).
4.5.6.3.1 Preparation of solutions.
4.5.6.3.1.1 Regular procedure.
a. Prepare a stock solution of solvent by dissolving 0.1 g of PBNA or other antioxidant in a
2-kg (5-pound) bottle of carbon disulfide.
b. Tare a 25-mL volumetric flask to the nearest 0.1 mg. Add 0.625 g of polymer to the flask
and reweigh the flask to ±0.1 mg. Care should be taken to prevent the polymer from sticking to
the lip or neck of the flask where solvent will not reach it. Add stock carbon disulfide to 2/3 final
volume. Allow to stand, with occasional shaking until the polymer is dissolved.
c. Check the solution thoroughly for gel. Gel occurs in two forms: "tight gel" which is
visible as definite particles and a "loose gel" which may be detectable only by the slight difference
in refractive index from the surrounding solution. When gel is present discard the solution and
use the alternate procedure of 4.5.6.3.1.2. When no gel is present, make the solution up to final
volume and shake well before sampling for scanning (see 4.5.6.3.2).
4.5.6.3.1.2 Alternate procedure. This procedure shall be used instead of that in 4.5.6.3.1.1
for those samples which are found in the regular procedure to contain gel.
a. Weigh 1.3 g of polymer into a small bottle and add 50 mL of stock carbon disulfide.
Allow to stand with occasional shaking until the polymer is dissolved. Examine the solution
carefully for gel. If any is present, remove it by filtration.
b. Tare a small (25 mL) vial to the nearest 0.1 mg. At the time the infrared cells are filled,
withdraw 10.0 mL of the solution with a pipet and place in the tared vial. Place the vial in a hood
and allow the solvent to evaporate. Remove the last traces of solvent overnight in a vacuum
desiccator. Weigh the vial to the nearest 0.1 mg and subtract the tare weight to obtain the weight
of the solids. The concentration of the solution in g/L is 100 times the weight of the residue in
grams.
4.5.6.3.2 Scanning of samples. Calibrate the instrument for electrical balance and the 100
percent T line. Set the zero percent T line to coincide with that of the chart paper. When these
checks are completed, the instrument is ready for scanning.
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