NPFC - MIL-DTL-25988
RUBBER, FLUOROSILICONE ELASTOMER, OIL-, HYDRAULIC FLUID-, AND FUEL-RESISTANT, SHEETS, STRIPS, MOLDED PARTS, AND EXTRUDED SHAPES
|Publication Date:||21 January 2021|
This specification covers a fluorosilicone (FVMQ) rubber in the form of molded rings, compression seals, O-ring cord, and molded-in-place gaskets and rubber sheets, strips, molded parts and extruded shapes for aeronautical and aerospace applications. This material is not suitable for use in synthetic phosphate ester based hydraulic fluids and generally not suitable for use in MIL-PRF-7808, MIL-PRF-23699 gas turbine lubricants or DOD-PRF-85734, MILPRF-32538 helicopter transmission lubricants. In future designs it is recommended to not use silicone sealing material in engine oil systems.
This fluorosilicone (FVMQ) has resistance to hydraulic fluids, gas turbine engine oils, and fuels, but usage is not limited to such applications. This fluorosilicone (FVMQ) has a typical service temperature range of -70 to 392 °F (-56.7 to 200 °C) for Class 1 and Class 2 and -70 to 437 °F (-56.7 to 225 °C) for Class 3. The service temperature range of the material is a general temperature range, but the presence of particular fluids and specific design requirements may modify this range. Each application should be considered separately. It is the responsibility of the user to determine that this specification is appropriate for the environments (temperature range, fluid exposure, etc.) in which it is sought to be used.
Note: The evolution of synthetic ester engine oil formulations has resulted in the determination that fluorosilicone elastomers are no longer suitable for use in high thermal stability (HTS) lubricants. Therefore, this specification should not be used for new design with HTS synthetic ester fluid.
The fluorosilicone elastomer rubber should be of the following types, classes, and grades, as specified (see 6.2).
Type I - O-rings and other compression seals.
Class 1 - O-rings (available only in Grades 60, 70, and 80)
Class 3 O-rings (available only in Grade 75)
Type II - Molded parts (other than compression seals), sheets, strips, and extruded shapes.
Class 1 - General purpose
Grade 40 - Nominal 40 type A durometer hardness, Type II only.
Grade 50 - Nominal 50 type A durometer hardness, Type II only.
Grade 60 - Nominal 60 type A durometer hardness, Types I and II.
Grade 70 - Nominal 70 type A durometer hardness, Types I and II.
Grade 80 - Nominal 80 type A durometer hardness, Types I and II.
Class 2 - High-strength general purpose (available only in Grade 50), Type II only.
Class 3 - High modulus, increased temperature resistance (available only in Grade 75), Types I and II.
The rubber covered by this specification is for use where resistance to jet fuel and lubricating oil is required. The elevated test temperatures (see table II) were selected as the maximum... View More
The rubber covered by this specification is for use where resistance to jet fuel and lubricating oil is required. The elevated test temperatures (see table II) were selected as the maximum temperatures at which good reproducible laboratory data could be obtained. These temperatures do not necessarily indicate nor are they to be construed as the maximum operating temperatures at which these materials can be used.View Less