Silicone Rubber (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 different addition of side chains can achieve significant variations in properties. Silicones have excellent heat, ozone and corona resistance, very well dielectric stability, and resistance to many oils, chemicals, and solvents. And for all elastomers, silicones possess the best flexible property at low temperature. But it also has some weakness like low tensile strength, poor tear and wear resistance.
Cure system - Peroxide-Cured vs. Platinum cured
Standard silicone compounds are usually peroxide-cured. Platinum-cured compounds offer better flexible properties and very low volatile matter. Platinum-cured silicones usually are applied in medical system or other required low volatile matter, but they need to be produced in clean room and higher cost of platinum catalyzer so they are more expensive than peroxide-cured ones.
Other Common Variations
• Silicones can be formulated with only “white list” ingredients as specified in 21.CFR 177.2600 for use in applications where the elastomer will be in contact with food or beverages.
• Silicones can be submitted for approval by the National Sanitation Foundation (NSF) for use in drinking water applications.
• Silicones are usually used in automotive system like boots, oil filter valve, gasket in light….etc.
• Silicone parts can be used in medical system which especially require compliance to USP CLASS VI.
ASTM D 1418 Designation: Q, MQ, VMQ, PVMQ
ISO/DIN 1629 Designation: Q, MQ, VMQ, PVMQ
ASTM D2000 / SAE J 200 Codes: FC, FE, GE
Standard Color(s): Rust
Hardness Range: 25 to 90 Shore A
Relative Cost: Medium-High
Standard Low Temperature: -60°C / -76°F
Standard High Temperature: 225°C / 437°F
Special Compound Low Temperature: 100°C / -148°F
Special Compound High Temperature: 300°C / 572°F
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