Specification Grade Silicones

AMS-R-25988 Fluorosilicone

AMS-R-25988 fluorosilicone from ElastaPro meets the requirements of an SAE International specification that supersedes MIL-DTL-25988 and is used by the U.S. military. AMS-R-25988 covers rubber, fluorosilicone elastomer, oil-and-fuel-resistant, sheets, strips, molded parts and extruded shapes for aerospace/aeronautical use.

These specification-grade materials are classified by types, classes, and grades. These are the AMS-R-25988 fluorosilicones that ElastaPro makes.

  • AMS-R-25988 TY 2 CL1 GR40
  • AMS-R-25988 TY2 CL1 GR50
  • AMS-R-25988 TY2 CL1 GR60
  • AMS-R-25988 TY2 CL1 GR70

AMS-R-25988 Types

There are two main types based on intended use.

  • Type 1: Materials for O-rings (compression seals).
  • Type 2: Materials for molded parts (other than O-rings), sheets, strips, and extruded shapes.

ElastaPro makes Type 2 materials.

AMS-R-25988-Classes

Within each Type, there are two classes based on material strength and purpose.

  • Class 1: General-purpose fluorosilicones.
  • Class 2: Higher-strength fluorosilicones for more demanding general-purpose applications.

ElastaPro makes Class 1 materials.

AMS-R-25988 Grades

Grades are defined by the material’s durometer (hardness) on the Shore A scale.

  • Grade 40 (40 durometer)
  • Grade 50 (50 durometer)
  • Grade 60 (60 durometer)
  • Grade 70 (70 durometer)
  • Grade 75 (75 durometer)
  • Grade 80 (80 durometer)

ElastaPro offers Grades 40, 50, 60, and 70.

Key Performance Properties

Key performance properties for AMS-R-25988 fluorosilicone include:

  • Temperature range: Fluorosilicones maintain good flexibility at low temperatures (typical service down to −60 °C or lower, depending on formulation) and have upper operating limits up to ~175 °C (≈350 °F) in many cases.
  • Chemical & fuel/oil resistance: The fluorinated side groups substantially improve resistance to petroleum-based fuels, mineral oils, aliphatic/aromatic oils and solvents.
  • Good compression set and aging resistance: Fluorosilicones perform better than standard silicone in some oil/fuel immersion conditions.
  • Retention of physical/mechanical properties: After heat ageing, fluorosilicones show reasonable tensile strength retention.

Design and Traceability Considerations

Consider the following when designing elastomeric seals and gaskets from AMS-R-25988 fluorosilicones.

  • Grades and Durometers: Select the appropriate grade (hardness) based on seal design, compression set and application environment. Higher durometer grades provide higher stiffness and load-bearing but may sacrifice flexibility/low-temp sealing.
  • Testing and Traceability: Meeting AMS-R-25988 implies comprehensive testing: hardness, tensile, elongation, compression set, fluid immersion, fuel immersion (TT-S-735), low temperature retraction (ASTM D1329), aging (ASTM D573) etc.

ElastaPro offers fully-tested batches with Certificates of Analysis (COA) to help support aerospace/defense procurement. Traceability, batch control, and adherence to document control (revision levels) in these industries are essential.

When selecting a fluorosilicone for a seal in a fluid or fuel environment:

  • Ensure the chemical compatibility of the elastomer with the fluid (fuel, oil, solvent, hydraulic fluid). FVMQs are excellent for many hydrocarbon fuels but less so for ketones, brake fluids, strong acids/bases, hydrazine.
  • Design for expected temperature extremes (both high and low), pressure, dynamic vs static sealing.
  • Consider compression set and long-term aging: fluorosilicones generally show good retention but must be verified under conditions of immersion, cycling and temperature.
  • In extrusion/sheet usage, ensure the sealing surfaces and flange designs accommodate any swelling or volume change from fluid immersion.

Aerospace, Defense, and Other Demanding Applications

AMS-R-25988 fluorosilicones are widely used in aerospace/defense and other demanding industries.

  • Aerospace fuel and oil seals: In aircraft fuel systems, engine mounts, avionics housings, where exposure to jet fuels, hydraulic oils, lubricants and temperature cycling is expected.
  • Automotive & turbo systems: FVMQ elastomers are used in automotive turbocharger seals, engine oil systems and fuel hoses where standard silicone would degrade. Some commercial materials reference compatibility with di-ester engine oils.
  • Seals in harsh chemical/solvent environments: Because of improved hydrocarbon/solvent resistance (compared to standard VMQ), FVMQ can be used in instrumentation, chemical processing valves, gasket and pad materials.

Ask ElastaPro for AMS-R-25988 Fluorosilicone Rubber

ElastaPro produces military silicone and fluorosilicone materials at our Made in USA manufacturing facility, and in accordance with our ISO 9001:2105 and AS9100D certified Quality Management System (QMS). Contact us to request a quote, or for more information.