MIL-PRF-27404D
APPENDIX B
NON-VOLATILE RESIDUE (NVR)
B.1 SCOPE
B.1.1 Scope. This Appendix describes two methods for the determination of non-volatile residue
of the propellant. This Appendix is a mandatory part of the specification. The information contained
herein is intended for compliance.
B.2 METHODS
B.2.1 Dropwise method.
B.2.1.1 Procedure. Clean the unassembled apparatus with detergent and rinse thoroughly with
purified water. Dry the parts in an oven at 110°C. Assemble the apparatus as shown in Figure B-1. Fill
the water bath with purified water and turn on the heater. Adjust the water level of the bath to
approximately one-half inch below the lowest fitting and mark this level on the bath. When the bath
temperature reaches boiling, adjust the nitrogen purge to approximately 2 liters per minute (L/min) and
turn on the aspirator. With the sample delivery valve closed, the pressure in the apparatus should be
below 30 mmHg. Open the sample delivery valve slowly to adjust the apparatus pressure to
approximately 60 mmHg. Allow the apparatus to purge for approximately five minutes to remove traces of
water. Remove the water bath and dry the outside of the residue vessel with a clean lintless tissue.
Disconnect the aspirator from the apparatus and remove the residue vessel using a tissue to hold the
vessel. Wipe the outside of the vessel and place it near the analytical balance. After at least twenty
minutes, accurately weigh the residue vessel until the weight remains constant to ± 0.1 mg. Record the
weight. Reassemble the apparatus and close the sample delivery valve. Replace the water bath, adjust
the water level to the mark, and heat the water to boiling. Transfer 100 mL of propellant to the apparatus.
With the nitrogen purge in place, turn on the water aspirator and reduce the apparatus pressure to less
than 30 mmHg. Slowly open the sample delivery valve to admit propellant to the residue vessel and
adjust the flow such that the apparatus pressure does not exceed 60 mmHg (approximately 2 drops per
second). The quantity of propellant in the residue vessel should not exceed 2 - 4 mL at the equilibrium
evaporation rate. Adjust the sample delivery valve to maintain the evaporation pressure at less than 60
mmHg. After 100 mL of propellant have been evaporated (approximately 30 min), allow the residue
vessel to purge for an additional five minutes to ensure complete evaporation of volatile material.
Remove the water bath, disconnect the aspirator, wipe the outside of the residue vessel, and remove it
from the apparatus. Allow the residue vessel to stand near the analytical balance for at least twenty
minutes before weighing. Weigh the residue vessel as above, and record the weight. To clean the
residue vessel reflux 5 mL of 5N ACS grade H2SO4 (or equivalent) in the vessel for several minutes
followed by several rinses of purified water. The vessel may be dried as described above or by gently
heating the vessel with a burner while purging with dry nitrogen. Regardless of the drying method used,
allow at least twenty minutes for the vessel to equilibrate to ambient temperature and humidity before
weighing.
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