Silicone, also known as silicone, is a synthetic polymer that is made of smaller repeating chemical units (called monomers) that are bonded together in long chains. Silicones consist of a silicon-oxygen backbone, and "side chains" consist of hydrogen or a hydrocarbon group attached to a silicon atom. Because silicone's main chain contains no carbon, it is considered an inorganic polymer, and unlike many organic polymers, its main chain is made of carbon.


The silicon-oxygen bonds in the silicone backbone are highly stable and hold together more firmly than the carbon-carbon bonds found in many other polymers. As a result, silicones tend to be more heat resistant than traditional organic polymers.


The side chains of the silicone make the polymer hydrophobic, making it useful for waterproofing applications. Side chains, usually composed of methyl groups, also make it difficult for silicones to react with other chemicals and prevent them from sticking to many surfaces. These properties can be adjusted by changing the chemical group attached to the silicon-oxygen backbone.




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Discover history


Chemist Frederic Kipping first coined the term "silicone" to describe the compound he was researching and synthesizing in his laboratory. He believes that silicon and carbon have many similarities, so they can make compounds similar to hydrocarbon structures. He called these compounds "Silicone".


In the 1930s, a scientist at Corning Glass Factory sought to find a suitable material for use in the insulation of electrical components. Silicone resins are suitable for this application because of their ability to cure under thermal conditions, and the first commercial development has led to the widespread production of silicones subsequently.


Silicones in everyday life


Silicones are durable and easy to manufacture, and are stable over a wide range of chemical conditions and temperature ranges. In light of these advantages, silicones have become highly commercialized and are used in many industries, including: automotive, construction, energy, electronics, chemicals, coatings, textiles and personal care. The polymer has many other applications, from additives to printing inks to deodorants.




Pictured: Silicone
Types of organic silicon and their uses


There are several different forms of silicone, each with a different degree of crosslinking. The degree of cross-linking describes the degree of interconnection of the siloxane chains. The higher the degree of cross-linking, the harder the siloxane material is. This variable is directly related to the properties of the polymer such as its strength and its melting point. Common forms of silicone and some of its applications include:


Silicone oil, consisting of straight chains of non-crosslinked silicone polymers. These fluids have been found to be useful as ingredients in lubricants, paint additives and cosmetics.
Silicon gels have almost no cross-linking between polymer chains. Silicone gel is used in cosmetics to form a protective layer on the skin surface and help the skin to retain moisture. Silicone gels can also be used as materials for breast implants and soft parts of certain insoles.
Silicone elastomers, also known as silicone rubbers, have more cross-linking bonds between their polymer chains and therefore have rubber-like properties. Silicone rubber is used as insulators in the electronics industry, seals for aerospace vehicles, and oven gloves for baking.
Silicone resin, a rigid form of silicone, has a high crosslinking density. These resins are commonly used in building materials, such as heat-resistant coatings and weather-resistant materials.




Pictured: Mobile phone case with silicone material
Organosilicon toxicity


Because silicones are chemically inert and more stable than other polymers, they do not react with parts of the body. However, toxicity depends on factors such as exposure time, chemical composition, dosage level, type of exposure, chemical absorption and individual response.


Researchers have determined the potential toxicity of silicones by studying skin irritation, changes in the reproductive system, and mutations. Although there are several types of silicones that can irritate human skin, research has shown that exposure to standard amounts of silicones usually has little adverse effect.


key point


Silicone is a synthetic polymer that has a siloxane backbone and the "side chain" is hydrogen or a hydrocarbon group.
The silicon-oxygen backbone makes silicones more stable than the polymers of the carbon-carbon backbone.
Silicone is durable, stable and easy to manufacture. For these reasons, it has been widely used in many daily products.
Silicones contain silicon, which is a naturally occurring chemical element.
The properties of siloxanes change with increasing degree of crosslinking. Silicone oil without the degree of crosslinking has the lowest rigidity. Silicone resins with a high degree of crosslinking are the hardest.


References:


"Silicone toxicology." In Safety of Silicone Breast Implants, ed. Bondurant, S., Ernster, V., and Herdman, R. National Academies Press, 1999.