O-rings – Aerospace Fluorosilicones

The “Gold Standard” for Jet Fuel

Because of their good hydrocarbon compatibility and unmatched low temperature performance, fluorosilicone O-ring materials have become the standard seal materials for use in most jet fuel applications and many low temperature hydrocarbon hydraulic applications.

To meet the needs of multiple applications, Parker has three different hardnesses of fluorosilicone O-ring materials.

Extreme Low Temperature Performance

Fluorosilicones have long been used for their outstanding low temperature properties. With a functional temperature range of -100°F to +350°F (-73°C to +177°C), fluorosilicone rubber has the thermal stability to accommodate nearly all aerospace applications. This thermal stability comes from the silicone backbone that forms the base polymer chain.

Outstanding Fuel and Oil Resistance

Fluorosilicone rubber also has fluorinated side chains branching off of the silicone backbone that give it chemical compatibility that approaches that of fluorocarbon rubber; resistance to petroleum-based oils, greases, and fuels is excellent. Fluorosilicones have become the seal material of choice for handling jet fuel on commercial, military, and general aviation aircraft of all types. Testing in ASTM Fuel B (also called TT-S-735 Type III) shows good compatibility with aggressive hydrocarbon fuels.

In addition, fluorosilicone O-rings have found a niche in sealing fire-resistant synthetic hydrocarbon hydraulic fluids in static applications, expecially those used at low temperatures.

Good Rebound Resilience

Historically, fluorosilicones have not offered good short-term rebound resilience. When stretched to fit into a male O-ring gland, fluorosilicone materials tended to sag rather than snap back tight against the groove. These new fluorosilicone compounds exhibit dramatic improvements in this category. While there are no industry standard test procedures for this type of test, it can be easily observed. This improvement in rebound resilience should make automated assembly more feasible and decrease the incidence of torn O-rings during installation.

Other Properties

Fluorosilicones generally have poor mechanical properties. As a result, they wear quickly in dynamic applications and are easy to tear during installation. Fluorosilicones also have poor gas permeation resistance. In vacuum and pressurized gas applications, fluorosilicone O-rings will allow some gas to permeate through the seal over long periods of time.

LM159-70

-100°F to +350°F (-73°C to +177°C)
Standard fluorosilicone O-ring material

LM158-60

-100°F to +350°F (-73°C to +177°C)
Softer fluorosilicone O-ring material
Lower compressive loads than LM159-70
Lower insertion forces than LM159-70
Conforms better to rough surfaces than LM159-70

LM160-80

-90°F to +350°F (-68°C to +177°C)
Harder fluorosilicone O-ring material
Higher pressure rating than LM159-70

Typical Applications Include:

• Low temperature hydrocarbon-based hydraulic fluids

MIL-PRF-5606
MIL-PRF-83282
MIL-PRF-87257

• Aviation fuels down to -100°F (-73°C)

Download the Fluorocarbons (FKM) Polymers for Sealing Applications Resources

Download the Warranty

This warranty comprises the sole and entire warranty pertaining to items provided hereunder. seller makes no other warranty, guarantee, or representation of any kind whatsoever. All other warranties, including but not limited to, merchant ability and fitness for purpose, whether expressed, implied, or arising by operation of law, trade usage, or course of dealing are hereby disclaimed. Notwithstanding the foregoing, there are no warranties whatsoever on items built or acquired wholly or partially, to buyer’s designs or specifications.

Limitation of remedy: Seller’s Liability arising from or in any way connected with the items sold or this contract shall be limited exclusively to repair or replacement of the items sold or refund of the purchase price paid by buyer, at seller’s sole option. In no event shall seller be liable for any incidental, consequential or special damages of any kind or nature whatsoever, including but not limited to lost profits arising from or in any way connected with this agreement or items sold hereunder, whether alleged to arise from breach of contract, expressed or implied warranty, or in tort, including without limitation, negligence, failure to warn or strict liability.