MIL-PRF-121G
3.6 Identification of material. The specification number, type, manufacturer's name,
manufacturer's designation, month and year of manufacture, and lot number shall be clearly and
legibly marked using water-resistant ink on the backing surface of the material. The color of the
markings shall be red. This complete group of markings shall be continuous lengthwise and the
distance between groups of markings shall be not greater than 6 inches. A complete group of
markings shall appear once in each 12 inches of width of the roll. The letters and figures shall be
not less than 1/8 inch high (see 4.3.2.1).
3.7 Workmanship. Barrier material surfaces shall be free from any foreign matter. The
barrier material edges shall be cut and trimmed of any selvage. Barrier material shall be free
from holes, tears, cuts, sharp creases, wrinkles, or other imperfections (see 4.3.2.1).
3.8 Performance requirements. The performance of the barrier materials shall meet the
requirements specified in table I, when tested in accordance with 4.6.
TABLE I. Performance requirements.
TEST
PARAGRAPH
PROPERTY
REQUIREMENT
REFERENCE
Seam Strength
1. As received material sealed & tested:
4.6.2
a. At room temperature (separation-inches)
No separation
b. At 100°F and at 160°F (separationinches)
No separation
2. Sealed before aging at 160°F for 12
days and tested:
a. At room temperature (separation inches)
No separation
b. At 100°F and at 160°F (separationinches)
No separation
3. Sealed after aging at 160°F for 12 days and
tested:
a. At room temperature (separation-inches)
No separation
b. At 100°F and at 160°F (separationinches)
No separation
Waterproofness (as received and aged)
No delamination
4.6.4
No evidence of water leakage
Oil Resistance (as received and aged)
No delamination
4.6.1
No evidence of oil leakage
Puncture Resistance
4.6.1
Type I
6 lbs (min)
Type II
4 lbs (min)
Tensile Breaking Strength
4.6.1
Type I
25 lbs/in. width (each direction) (min. avg.)
Type II
17 lbs/in. width (each direction) (min. avg.)
Tearing Resistance
4.6.1
Type I
150 gms. (each direction) (min. avg.)
Type II
100 gms. (each direction) (min. avg.)
Resistance to Curl
No curl in excess of 5%
4.6.1
Aging Resistance
No delamination
4.6.3
4
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