MIL-DTL-25988 Type 2 Class 2 Grade 40 silicone from SSP is independently tested to ASTM requirements.
Specialty Silicone Products (SSP) submitted samples of two 40-durometer military / aerospace silicones to independent ISO 17025 accredited test laboratories. These samples were tested against commercial and military standards.Â
SSP-220 met the physical and mechanical requirements of A-A-59588, Class 2A and 2B, Grade 40.
SSP-267 met MIL-DTL-25988C, Type 2, Class 2, Grade 40 physical requirements.
The following sections describe the products and summarize the test results.
MIL-DTL-25988 Type 2 Class 2 Grade 40 silicone
SSP-267 is a 40-durometer (Shore A), peroxide-catalyzed, heat-cured fluorosilicone that meets MIL-DTL-25988, Type 2, Class 2, Grade 40 requirements and combines broad temperature resistance with resistance to fuels, coolants, and oils. According to MIL-DTL-25988, Type 2 fluorosilicones are for molded parts (other than O-rings), sheets, strips, and extruded shapes.  Â
SSP submitted samples of SSP-267 to the Physical Testing Department at ARDL, the Akron Rubber Development Laboratory. The table below shows how these samples passed the following tests.Â
| Standard | Description | Test Result |
| ASTM D412ASTM D2240ASTM D297 | Original Physical Properties | Pass |
| ASTM D624, Die B | Tear Resistance | Pass |
| ASTM D573 | Heat-Aged Properties | Pass |
| ASTM D395, Method B | Compression Set | Pass |
| ASTM D471 | Fluid Immersion Properties | Pass |
| ASTM D1329 | Low Temperature Retraction | Pass |
Contact SSP for more information.Â
MIL-DTL-25988 is a U.S. military detail (DTL) specification that covers fluorosilicones for aerospace applications. With their fluorine additions, these silicone elastomers resist petroleum-based fuels and oils, solvents, and harsh chemicals. MIL-DTL-25988 fluorosilicones also withstand a wide range of temperatures and maintain their tear and tensile strength when immersed in jet fuel. These fuel-resistant materials can withstand repeated flexing without stress cracking and remain flexible and rubbery.
The MIL-DTL-25988 specification divides compliant fluorosilicones into different types, classes, and grades. Type 1 materials are for O-rings and Type 2 materials are for sheets, strips, and extruded shapes. Type 2 fluorosilicones are also used in molded parts except for compression seals. Class 1 materials are designated for general-purpose use and Class 2 materials are high-strength compounds. The grades for MIL-DTL-25988 fluorosilicones correspond to the material’s durometer.
