Silicones are primarily based on a strong sequence of silicon and oxygen atoms. This silicon-oxygen backbone is much stronger than a carbon-based backbone, making silicones more resistant to extreme temperatures (-65° to +450° F, -54° to +232° C), chemicals, and shearing stresses.
Due to saturation in the polymer’s main chain, silicones are very resistant to oxygen, ozone, and UV light. This same saturation also demands that the material be peroxide cured since it is not possible to sulfur cure a saturated polymer. In addition to being generally inert (non-reactive), silicones are odorless, tasteless, non-toxic, and fungus resistant. They also have great flexibility retention and low compression set.
There are four primary silicone formulations in use today. Standard methyl silicone is known simply as MQ. By replacing a small number (typically less than 1%) of the pendant methyl (CH3) groups in MQ with vinyl (CH2CH) groups, you arrive at what is known as vinyl methyl silicone, or VMQ. VMQ compounds tend to have better cure properties and undergo lower compression set than standard MQ.