Silicones are high-performance oligomers or polymers that can take a variety of physical forms, ranging from solids to water-thin liquids and semi-viscous pastes, greases and oils.
They are noted for their ability to function in conditions that would literally destroy conventional material. Silicones display a host of unique properties that can lubricate, seal, bond, release, defoam and encapsulate. They can even insulate, waterproof and coat. They conduct electricity. They won't harden, crack peel, crumble or dry out, rot or become brittle with age.
Properties
- Silicones exhibit many useful properties, including:
- Low thermal conductivity
- Low chemical reactivity
- Low toxicity
- Thermal stability (constancy of properties over a wide temperature range of −100 to 250 °C).
- The ability to repel water and form watertight seals, although silicones are not hydrophobes.
- Does not stick to many substrates, but adheres very well to others, e.g. glass.
- Does not support microbiological growth.
- Resistance to oxygen, ozone, and ultraviolet (UV) light. This property has led to widespread use of silicones in the construction industry (e.g. coatings, fire protection, glazing seals) and the automotive industry (external gaskets, external trim).
- Electrical insulation properties. Because silicone can be formulated to be electrically insulative or conductive, it is suitable for a wide range of electrical applications.
- They have high gas permeability: at room temperature (25 °C), the permeability of silicone rubber for such gases as oxygen is approximately 400 times[citation needed] that of butyl rubber, making silicone useful for medical applications in which increased aeration is desired. Consequently, silicone rubbers cannot be used where gas-tight seals are necessary.
Application
Silicones, in their many forms, are used in the following sectors:
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