MIL-PRF-43906D
multidirectional cycles. The specimen shall then be tested for hydrostatic resistance in
accordance with 4.4.1 with the abraded portion of the specimen centered in the hydrostatic
test area.
4.4.3 Resistance to high humidity. Three 4 by 4-inch specimens shall be laid flat, face side
up, on a supporting plate and the assembly placed in a desiccator containing water in the
lower portion. The water level shall be approximately 1 inch below the specimens. The lid of
the desiccator shall be put in place and the desiccator placed in a circulating air oven having a
temperature of 125°F + 2°F for a period of seven days. At the end of the aging period, each
specimen shall be removed from the desiccator, visually examined for colorfastness and for
resistance to high humidity and then tested immediately in accordance with 4.4.1.
4.4.4 Stiffness
4.4.4.1. TAPPI Method T-451, Preferred Procedure (1).
4.4.4.2 The stiffness test shall be conducted as specified in 4.4.4.1 except that the apparatus
and test specimens shall be subjected to a temperature of 0°F + 2°F for a period of 4 hours
and the test shall be performed in a still atmosphere at that temperature.
4.4.5 Accelerated weathering. AATCC Method 169 except that the deviations shown below
shall apply. At the end of the accelerated weathering exposure period, each specimen shall
be visually examined for colorfastness and for resistance to accelerated weathering and then
tested for hydrostatic resistance.
Deviations to AATCC Method 169:
a. The test apparatus shall be either test chamber type 1A or IB. Type 1B shall be equipped
with a three-tiered inclined specimen rack. The apparatus shall be equipped with an
automatic light monitor and shall be capable of automatically controlling irradiance,
temperature, and humidity. The apparatus shall be maintained in accordance with the
manufacturer's recommendations.
b. The weathering test cycle shall be 40 minutes of light, 20 minutes of light with water spray
on the fabric face, 60 minutes of light, 60 minutes of darkness. The test cycle shall be
repeated until the total energy exposure is equal to 100 kilojoules per square meter.
c. The irradiance level shall be 0.55 + 0.01 watt/square meter/nanometer (w/m2/nm)
bandpass at 340 nanometers.
d. The glass filter combination shall be a quartz inner filter and a borosilicate type "S" outer
filter.
e. The relative humidity shall be 50 + 5 percent during the light cycle and not lower than 95
percent during the dark cycle.
f. The control set points shall be as follows:
Dark cycle
Light cycle
Black panel
38°C
77°C
Conditioning water
40°C
53°C
Wet bulb depression 1/
0°C
10°C
1/ As a guide only; adjust to achieve required relative humidity (see e. above).
g. The test specimens shall fit smoothly on the specimen rack of the apparatus with no
wrinkles or gaps. The test specimen shall be mounted to the outside of the rack with the
use of appropriate stainless steel spring clips (see 6.7). After the required exposure period,
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