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

Silicones have an inorganic silicon-oxygen (Si-O) backbone and are defined as inorganic or hybrid substances. They can contain organic components such as oxygen, hydrogen and carbon [1].

Silicone polymers have a wide range of chemical and physical properties, and can be manufactured in many forms, including [1]:

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

Some of the chemical and physical properties of silicones include[1]:

• 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

Benefits

Silicones can be made to resist moisture, chemicals, heat, cold, and ultraviolet radiation. Silicones also display a host of unique properties that can lubricate, seal, bond, release, defoam, spread, and encapsulate. They can even insulate, waterproof, and coat [1].

Applications

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 [1].

The Commonwealth Scientific and Industrial Research Organisation (CSIRO) has found that silicone has enormous potential for 3D printing and has applications in medical devices and customised products such as dental devices, hearing aids and cochlear implants, prosthetics, and other patient specific medical devices [2].

Silicone products are used extensively in the energy sector in renewable energy sources like solar panels and wind turbines, as well as traditional energy sources like oil, gas and electricity. Silicones are used as conductive adhesives and encapsulants in the manufacturing of solar panels. Their resistance to UV radiation and temperature changes and superior transparency improve panel efficiency, while their mechanical and chemical properties reduce repair costs and ensure panels last longer. Silicones are also used as bonding agents and lubricants in the manufacture of wind turbines. They increase the durability and weather resistance of rotor blades, and the lubricants help reduce maintenance costs and maximise energy efficiency [3].

Sustainability

The use of silicones in industrial and consumer applications affords a range of useful product performance characteristics including facilitating products to last longer, providing flexibility or rigidity, and the ability to withstand extreme temperatures and humidity, thus reducing the resource and energy consumption of the products in which silicones are used [4].

Health

Silicone materials have been subject to hundreds of scientific studies showing that they are safe for human health, when used for their intended purposes. Risk evaluations have been conducted by several regulatory agencies such as Australian Departments of Environment and Health, Health Canada, UK regulatory bodies, as well as expert scientific panels such as the Cosmetic Ingredient Review and the EU Scientific Committee on Consumer Safety. All of these risk assessments concluded that there is no risk to human health from silicone materials when used as intended [5].

Environment

The Silicones Industry continues to evaluate the science behind its materials, studying the fate and effects of silicone materials in the environment.  Silicone materials have been subject to hundreds of scientific studies showing that they are safe for the environment, when used for their intended purposes [6].

Global Silicones Council

The Global Silicones Council (GSC) brings together all the major global manufacturers via the three Regional Silicone Industry Associations (RSIAs) located in North America, Europe, and Japan. Chemistry Australia is an affiliated association of the GSC.

Further information on regulations and safety for silicones can be found on the GSC website.