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
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.