Aerospace Seal Materials: A Fluid-by-Fluid Guide from Jet Fuel to Hypergolic Propellants

Choosing aerospace seal materials starts with one question: what fluid will the seal touch? Some fluids are mild, like petroleum hydraulic oil. Others, like hypergolic propellants, attack almost every elastomer. As a result, the wrong choice can lead to swelling, cracking, or leaks.

This guide walks through three common fluid groups:

• Aviation hydraulic fluids
• Jet fuels
• Hypergolic rocket propellants

For each one, we cover which aerospace seal materials fit and why. We also share NASA test data for the toughest group. Finally, we cover design factors that apply across all three.

Quick Selection Table

Use this table as a starting point. Then confirm the details below for your specific application.

Aviation Hydraulic Fluids: MIL-SPEC Compounds

Military and aerospace hydraulic systems usually call out a specific material spec. Therefore, the first step is to match the spec on your drawing.

Marco offers several compounds for these systems:

M1000: A 70 durometer nitrile made to MIL-P-25732, suited to military aircraft hydraulics at low temperatures.
M1001: A 75 durometer, peroxide-cured nitrile made to AMS-P-83461.
M1002: A nitrile made to AMS-P-5315, used for MS29513 and MS29512 boss and tube sizes.
V1002: A 75 durometer black FKM made to AMS-7276 and MIL-R-83248C.
V1004 and V1005: Additional FKM options for higher-temperature hydraulic service.
Z1217: A Markez® FFKM for jet engine and APU applications that meets AMS-7257.

For the full list of specs, see Marco's O-ring Mil-Spec chart.

Jet Fuel: Fluorosilicone Compounds

Jet fuel calls for a different material. Fluorosilicone is a common choice. It combines fuel resistance with strong low-temperature flexibility.

Marco's jet fuel compounds include F1001, F1002, F1003, and F1004. For example, F1001 is a 70 durometer blue fluorosilicone per AMS-R-25988, with jet fuel resistance and a range of -100 °F to 350 °F.

However, fluorosilicone has limits. Marco's fluorosilicone datasheets list hydrazine among the material's limitations. In other words, a seal that works well in jet fuel can fail in a rocket propellant system. That brings us to the most demanding fluid group.

Hypergolic Propellants: The Toughest Test for Seals

Hypergolic systems pair a fuel with an oxidizer. The two ignite on contact, with no spark needed. This makes them reliable for thrusters and orbital maneuvering. Yet the same reactivity makes them punishing for hypergolic fuel seals.

Common hypergolic media include:

MON-3 (Mixed Oxides of Nitrogen): A mixture of dinitrogen tetroxide and nitrogen dioxide. It is a strong oxidizer.
MMH (Monomethyl Hydrazine): A hydrazine-based fuel that attacks many common rubber compounds.

These fluids are extremely hazardous. Most commercial labs cannot safely run immersion tests in them. For this reason, independent NASA data is especially valuable.

The Standout Material: Freudenberg-NOK Simriz® 486

Simriz® 486 is a white, 75 Shore A FFKM compound from Freudenberg-NOK Sealing Technologies. It was engineered for aggressive oxidizer and fuel environments. Most importantly, it has NASA test data to back it up.

When samples of Simriz® 486 were submitted to the NASA White Sands test facility, the results were clear:

In short, Simriz® 486 is good for use in both media. Consequently, NASA gave it an "A" compatibility rating in MON-3 and MMH. The material also meets the requirements of NASA-STD-6001B Test 15 with no chemical changes.

Simriz® 486 Properties

Low compression set matters here. It means the seal holds its sealing force longer. As a result, service life improves and replacement intervals shrink.

Chemical Resistance Beyond Propellants

Simriz® 486 also resists many other fluids. The datasheet rates it "++" (excellent) in:

• Dinitrogen tetroxide and hydrazine isomers
• Hot water and steam
• Alkalis, bases, amines, and hot amines
• Ketones, esters, ethers, and aldehydes
• Hot lubricants, synthetic oils, fluorinated fluids, and alcohols

It is rated "+" (good) in dry heat and inorganic acids such as nitric acid. Therefore, one compound can often serve both the flight system and its ground support equipment.

Where Simriz® 486 Fits

Typical applications include:

• Satellite propulsion and orbital maneuvering systems
• Rocket engine support systems
• Propellant valves and pressure regulators
• Thruster assemblies
• Fuel and oxidizer handling equipment
• Propellant transfer systems and ground support equipment

One note: the low limit is -7 °C (+20 °F), so confirm that your mission profile and cold-soak conditions stay in range.

Design Factors for Aerospace Seal Materials That Apply to Every Fluid

The right aerospace seal material is only half the job. Next, the gland design has to support it.

Preventing O-Ring Extrusion

Extrusion is a common failure in high-pressure aerospace systems. It usually comes from three causes:

Incorrect hardness: A soft compound may not resist the pressure.
High pressure: Pressure pushes the O-ring into the clearance gap.
Excessive extrusion gap: Loose tolerances give the O-ring room to escape.

To address this, start with correct gland dimensions. Marco's O-ring groove design directory and groove design considerations guide cover squeeze, stretch, and fill.

In addition, consider back-up rings. Marco recommends them above 1,500 psi or with large extrusion gaps, since they close or reduce that gap. Learn more on Marco's back-up rings page.

Documentation and Traceability

Aerospace buyers often need proof, not just performance. Before you qualify a seal, ask your supplier for:

• Material certifications tied to the governing spec
• Lot traceability back to the compound batch
• Fluid compatibility data for your actual media

Finally, always test the finished part in your application. Lab data is a starting point, not a guarantee.

Sourcing Aerospace Seals and Materials Through Marco

Marco Sealing Solutions is an approved Freudenberg-NOK distributor. Freudenberg-NOK Sealing Technologies is the only vertically integrated manufacturer of perfluoroelastomer materials. It controls the full value chain, from monomers to finished seals. This supports consistent quality and traceability for compounds like Simriz® 486.

Freudenberg-NOK's Approved Distributor status recognizes distributors that meet its standards for technical competence, service quality, and integrated logistics. Marco also provides engineering and supply support. Read more about what Marco's Freudenberg-NOK Approved Distributor Status Means for You.

With Marco, you get:

• Stocked Simriz® 486 O-rings in AS568 sizes, such as Z486-150
• MIL-SPEC nitrile, FKM, fluorosilicone, and FFKM compounds in one place
• Application engineering and failure analysis support
• Access to the full Freudenberg Simriz® FFKM portfolio

Frequently Asked Questions About Aerospace Seal Materials

What sealing solutions meet MIL-SPEC requirements for aerospace hydraulic systems?

Marco offers V1002, V1004, V1005, M1000, M1001, M1002, and Z1217. Each matches a specific AMS or MIL spec. See the hydraulic fluid section above for details.

Which rubber compounds are rated for jet fuel and aviation hydraulic fluid exposure?

For aerospace seal materials compatible with jet fuel, consider fluorosilicones F1001, F1002, F1003, and F1004. For hydraulic fluid, consider V1002, V1004, V1005, M1000, M1001, M1002, and Z1217.

What causes O-ring extrusion in high-pressure hydraulic aerospace systems?

The three main causes are incorrect hardness, high pressure, and an excessive extrusion gap. Proper groove design and back-up rings help prevent it. For example, Marco stocks PTFE back-up rings in solid, split, and spiral styles to military standards such as MS28774, MS27595, MS28782, and MS28783. Marco also offers contoured 90 durometer nitrile and FKM back-up rings in AS568 sizes. Need something different? Custom sizes and materials can be made to order, so contact Marco for selection and design help.

Which seal material works in nitrogen tetroxide and hydrazine?

Simriz® 486 FFKM. NASA testing showed no deterioration of properties in MON-3 or MMH. As a result, it earned an "A" rating in both.

Can I use a jet fuel O-ring in a hydrazine system?

Usually not. Fluorosilicone handles jet fuel well, but hydrazine is a known limitation. Instead, choose a material with hypergolic test data, such as Simriz® 486.

Need Help Matching a Material to Your Fluid?

Every aerospace fluid brings its own challenges. Fortunately, you don't have to sort through them alone. Marco's engineers can help you match the right compound to your system, from hydraulic lines to thrusters.

Request a quote for Simriz® 486 or contact Marco's engineering team to discuss your needs and find the right aerospace seal materials for your application.

The information contained herein is believed to be reliable, but no representations, warranties or guarantees of any kind are made as to its accuracy or suitability for any purpose. The information is based on laboratory testing and is not necessarily indicative of the performance of the final product. The user is responsible for performing complete testing and for the performance of the final product.

Related Reading

MIL Spec Compounds
Groove Design Guide Directory
Back-Up O-Rings Designed for Higher-Pressure Applications
Freudenberg-NOK Approved Distributor Status: What It Means for You