MIL-DTL-45301E
contamination, porosity, delamination or lack of adhesion. Any undercutting shall be not in
excess of 0.25 in. (6.35 mm) deep (see 4.9.1.3 and 6.6).
TABLE III. Mechanical and physical properties.
Tie gum and tread elastomer
requirements, all classes
Group B,
Properties
Group A
Group B
P-12 material
Before aging
Hardness (Durometer, Shore A, or IRHD)
73 + 5
72 + 7
73 + 5
Tensile strength min. pounds per square
2100 (14 480)
3000 (20 685)
2700 (18 620)
inch (psi) [kiloPascals (kPa)]
Ultimate Elongation, percent
200 minimum
400 minimum
350 minimum
Modulus, 200 percent min. psi (kPa)
1600 (11 030)
--------
-------
Modulus, 300 percent min. psi (kPa)
--------
--------
2000 (13 790)
Modulus, 400 percent min. psi (kPa)
--------
2000 (13 790)
--------
Specific gravity
1.190 max.
1.200 max.
1.170 max.
Ozone resistance
7 day duration
7 day duration
7 day duration
-40°C (-40°F)
-40°C (-40°F)
-40°C (-40°F)
Low temperature flexibility
After accelerated aging
Tensile strength min. psi (kPa)
-------
-------
2500 (17 240)
Tensile strength change (percent)
+ 25
+ 25
-------
Elongation change (percent)
+ 35
+ 35
-------
TABLE IV. Curing characteristics. 1/
Tread elastomer and tie gum
After aging 7 days 158°F (70°C)
Mooney units
Before aging
Initial reading, max. Mooney units
60
100
4 minute reading, max. Mooney units
40
60
Minutes to 5 point rise, maximum
65
65
Minutes to 5 point rise, minimum
35
19
1/ This table covers the curing characteristics of classes 1, 2, 3 and 5 elastomers and tie
gum, and classes 4 and 6 after mixing, using the shearing disk viscometer
(ASTM D1646), small rotor, 250°F (121°C), for measuring the Mooney viscosity of
the applicable elastomers and tie gums. To determine the uniformity of heavy extruded
stocks 1 in. (25.4 mm) and above in thickness, Mooney test specimens will be prepared,
0.25 in. (6.4 mm) in thickness and 1.75 in. (44.5 mm) in diameter, from the surface and
inner center of the stock. The difference between the Mooney results shall be not more
than 10 minutes to the five point rise. Tie gum can be stripped from tread elastomer
8
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