Silicones (VMQ) have good heat resistance and cold flexibility, weathering resistance, and good insulating and physiologically neutral properties. Compared to silicone, fluorosilicones (FVMQ) have fluorinated side chains for good oil and fuel resistance.
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.
FVMQ, as their name suggests, have similar polymer structure as VMQ, but with the additional trifluoropropyl substituent group on the polymer chain (yellow frame). This extra substituent gives the end product excellent resistance to many fuels (aliphatic and aromatic), solvents (benzene, toluene, ..), oils (animal, vegetable, mineral, silicone, …) and chemicals which would severely degrade VMQ and most other polymers.
The mechanical and physical properties are very similar to VMQ. However, FVMQ offer poor hot air resistance when compared with VMQ. Compared to Fluorocarbon rubbers fluorosilicones provide a much wider operational temperature range as they can reach temperatures up to 175°C and go as low as -70°C. In some cases, however, high temperature range in fluids is limited due to possible degradation of fluid and formation of harmful acids.
FVMQ Is for example used in:
