Fluorosilicone was invented by Dow Corning in the early 1950’s. The international nomenclature for fluorosilicone rubber is FVMQ. FVMQ polymers are built of polysiloxane chains where methyl side groups are replaced by trifluoropropyl side groups. Therefore they have nearly the same mechanical and physical properties as silicone rubber but due to the fluorination they show better resistance against many fluids. FVMQ polymers typically contain 23-28 % Fluor. FVMQ has a good heat resistance, very good low temperature flexibility and excellent resistance to weather, ozone and UV rays. Compared to VMQ the temperature range is slightly reduced from -50°C to 180°C.
Producers of FVMQ are Dow Corning with tradenames Silastic and Xiameter, Shin-Etsu, and Weihai New Era Chemical.
The figures below show typical structures for a fluorosilicone copolymer:
Fluorosilicones are available with a wide range of physical properties. They show good resistance against automotive and aerospace oils, fuels and fluids and against a wide range of other chemicals/solvents.
The elongation at break and tensile strength of FVMQ and FPM at different temperatures has been measured. Elongation of FVMQ is far less affected by temperature than the one for FKM. Tensile strength for FKM is in general better.
Due to relatively low tear strength, high friction and limited abrasion resistance of these materials, they are generally recommended for static applications only.
FVMQ rubber compoud is resistant against
• Automotive fuels (gasoline leaded/unleaded, diesel, RME and various test fuels)
• Mineral and synthetic oils
• ATF (automatic transmission fluid)
• Jet fuels and oils
• Various other chemicals and many solvents
General resistance data for FVMQ in some fluids are given in the table below:
Fuel swell of FVMQ and FKM types in FAM-B has been compared. With the proper choice of a FKM type better values can be obtained than for FVMQ.
Also the permeability of FVMQ to fuels is much higher than for FKMs, as is shown in the graph below.
As a consequence its more general use is limited by its high gas permeability, low tensile strength and poor resistance to tear and abrasion. Typical uses are in static seals in aerospace fuel systems, and in automotive for diaphragm valves for crankcase ventilation.
FVMQ can be used in a temperature range from -50°C to +180°C, with short term exposure up to 200°C.
It remains flexible and keeps its sealing force down to -50°C and shows good retention of properties at higher temperatures.
A comparison of the TR10 values of different FVMQ and FPM types is given below:
FVMQ FE-281 -57°C
FPM Viton B -13 °C
Viton GFLT -24 °C
VPL85540 -40 °C
It is obvious that Tg and TR10 values are much lower for the FVMQ types.
This is also demonstrated by the DMA curves of FKM and FVMQ in the figure below.
More information about FVMQ rubber compounds
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