MIL-DTL-25988C
TABLE II. Physical properties, type I (O-rings).
Class 1
Class 1
Class 1
Class 3
grade 60
grade 70
grade 80
grade 75
Original Properties
Specific gravity
As determined 1/
As determined 1/
As determined 1/
As determined 1/
Hardness, points
60 ±5
70 ±5
80 ±5
75 ±5
Tensile strength, psi, min.
700 (4.83 kPa)
750 (5.17 kPa)
750 (5.17 kPa)
700 (4.83 kPa)
Elongation, %, min.
150
125
70
90
Temperature retraction, °F, max.
70 (56.7 °C)
70 (56.7 °C)
70 (56.7 °C)
70 (56.7 °C)
After air aging 70 hours @ 75 ±5 °F (23.9 ±2.8 °C)
Compression set, %, max.
Under 0.110 inch (2.79 mm)
20
15
25
25
Over 0.110 inch (2.79 mm)
15
15
20
20
After aging 70 hours @ the temperatures indicated:
392 ±5 °F
392 ±5 °F
392 ±5 °F
437 ±5 °F
(200 ±2.8 °C)
(200 ±2.8 °C)
(200 ±2.8 °C)
(250 ±2.8 °C)
Hardness change, point, max.
+10, 5
+10, 5
+10, 5
+10, 5
Tensile strength decrease, %, max.
25
25
20
35
Elongation decrease, %, max.
25
25
20
45
Weight loss, %, max.
2
2
2
2
After air aging 22 hours @ 347 ±5 °F (175 ±2.8 °C)
Compression set, %, max.
Under 0.110 inch (2.79 mm)
45
30
50
45
Over 0.110 inch (2.79 mm)
40
30
45
35
7
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