Silicone (MQ, VMQ, PVMQ)
Physically, silicones are based on silicon, an element derived from quartz. To create this class of synthetic elastomers, pendant organic groups such as methyl, phenyl, and vinyl are attached to silicon atoms. The addition of side chains can achieve significant variations in properties.
Excellent heat, ozone, and corona resistance
High dielectric stability
Resistance to many oils, chemicals, and solvents
Of all elastomers, silicones possess the best property of flexibility at low temperatures. However, silicones also have some weaknesses like low tensile strength, and poor tear and wear resistance.
Silicone is found:
In contact with food or beverages as elastomers that pass the 21.CFR 177.2600 specification
In medical systems which require compliance to USP CLASS VI
Automotive systems like boots and oil filter valves
Standard Compound: -60°C (-76°F) to 225°C (437°F)
Special Compound: -100°C (-150°F) to 300°C (572°F)
Hardness: 25 to 90 Shore A
ASTM D1418 Designation: Q, MQ, VMQ, PVMQ
ASTM D2000 Designation: FC, FE, GE
Standard Colors: Rust
Standard silicone compounds are usually peroxide-cured. Platinum-cured compounds offer better flexibility and very low volatile matter, and are usually applied in medical systems or other areas that require low volatile matter. However, they need to be produced in a clean room with the more expensive platinum catalyzer, so they are more expensive than those cured with peroxide.
Silicones perform well in engine and transmission oil (mineral oil), diluted salt solutions, moderate temperature water, dry heat, ozone environments, and are weather resistant.
Silicones do not work well in concentrated acids and alkalis, petroleum oils/fuels, ketones, and in steam environments over 120 °C.