What Are Silicones?

What Are Silicones?

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“Silicone” is a generic term referring to a class of synthetic polymers that are based on a framework of alternating silicon and oxygen (siloxane) bonds with at least one organic group attached to the silicon atom via a direct carbon-silicon bond.

Although silicones can contain organic components such as oxygen, hydrogen, and carbon, they have an inorganic silicon-oxygen (Si-O) backbone and are defined as inorganic or hybrid substances. This Si-O backbone makes the physical and chemical properties of silicones very different from the properties of similar carbon-based (organic) chemical substances that have an organic carbon (C-C) backbone.

Unique Properties

Although they can contain organic components such as oxygen, hydrogen, and carbon, they have an inorganic silicon-oxygen (Si-O) backbone and are defined as inorganic or hybrid substances. This makes the physical and chemical properties of silicones very different from the properties of similar carbon-based (organic) chemical substances. Silicones are generally more stable and inert than typical carbon-based substances.

Silicone polymers have an exceptional breadth of chemical and physical properties, and can be manufactured in many forms, including:

  • Solids
  • Liquids
  • Gels
  • Pastes
  • Greases
  • Oils
  • Rubber

Many Forms

The backbone of inorganic silicon and oxygen atoms, combined with the organic side chain functionality provides silicones with the unusual combination of physical/chemical properties including:

  • High hydophobicity/lipophilicity
  • Low water solubility
  • Volatility (high vapor pressure relative to organic compounds of the same size and high air/water partitioning [Henry Constant])
  • Large molecular size
  • Very low polarizability
  • Significant hydrogen bond acceptor character
  • Higher bond strength of Si-O bond compared to Si-C bond

Performance in Harsh Conditions

Silicones can be made to resist moisture, chemicals, heat, cold, and ultraviolet radiation. They are noted for their ability to function in conditions that would destroy conventional materials. Silicones display a host of unique properties that can lubricate, seal, bond, release, defoam, spread, and encapsulate. They can even insulate, waterproof, and coat. They do not conduct electricity and will not harden, crack, peel, crumble or dry out, rot, or become brittle with age.

Because of these and other properties, silicone polymers are utilized in thousands of products in applications such as construction, consumer products, electronics, energy, healthcare, and transportation. These polymers provide unique product performance characteristics that enable innovation in thousands of products that benefit key segments of the global economy and are critical for achieving environmental sustainability targets.

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Silicone Chemistry
Benefits & Uses