Silicone, also known as silicone, is a synthetic polymer, a material made from smaller repeating chemical units called monomers that are bonded together in long chains. Silicones are made up of a silicon-oxygen backbone, with “side chains” made up of hydrogen or hydrocarbon groups attached to silicon atoms. Because silicone’s backbone contains no carbon, it is considered an inorganic polymer, unlike many organic polymers whose backbone is made of carbon.
The silicon-oxygen bonds in the silicone backbone are highly stable and hold together more strongly 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 silicone make the polymer hydrophobic, allowing it to be used in water-repellent applications. Side chains, often composed of methyl groups, also make it difficult for silicone to react with other chemicals and prevent it from sticking to many surfaces. These properties can be tuned by changing the chemical groups attached to the silicon-oxygen backbone
Chemist Frederic Kipping first coined the term “silicone” to describe the compound he was studying and synthesizing in his laboratory. He believed that silicon and carbon had many similarities and therefore could make compounds similar to hydrocarbon structures. He called these compounds “silicone”.
In the 1930s, a scientist at the Corning Glass Works Company was trying to find a suitable material to use in insulation for electrical components. Silicones were suitable for this application because of their ability to cure under thermal conditions, and their first commercial development led to the subsequent widespread production of silicones.
Silicones in Daily Life
Silicones are durable, easy to manufacture, and stable across a wide range of chemical conditions and temperature ranges. Given these advantages, silicones have become highly commercialized and used in many industries including: automotive, construction, energy, electronics, chemicals, coatings, textiles, and personal care. The polymer also has a variety of other applications, from additives to printing inks to deodorants.
There are several different forms of silicone, and they vary in their degree of cross-linking. The degree of cross-linking describes how interconnected the silicone chains are; the higher the degree of cross-linking, the harder the silicone material is. This variable is directly related to properties such as the strength of the polymer and its melting point. Common forms of silicones and some of their applications include:
Silicone oil consists of straight chains of uncrosslinked silicone polymers. These fluids have found use as lubricants, paint additives, and ingredients in cosmetics.
Silicone gel has almost no cross-links between its polymer chains. Silicone gel is used in cosmetics to form a protective layer on the skin’s surface, helping the skin retain moisture. Silicone gel is also used as a material for breast augmentation implants and the soft parts of some insoles.
Silicone elastomers, also known as silicone rubber, contain more cross-links between their polymer chains, giving them rubber-like properties. Silicone rubber is used as an insulator in the electronics industry, seals in aerospace vehicles, and oven mitts for baking.
Silicone resin, a rigid form of silicone, has a high cross-link density. These resins are commonly used in construction materials such as heat-resistant coatings and weather-resistant materials.
Because silicones are chemically inert and more stable than other polymers, they won’t react with body parts. However, toxicity depends on factors such as exposure time, chemical composition, dose level, type of exposure, chemical absorption, and individual response.
Researchers determined the potential toxicity of silicones through studies of skin irritation, reproductive system changes and mutations. Although there are several types of silicones that can irritate human skin, research shows that exposure to standard amounts of silicones generally has few adverse effects.
Key Points
Silicone is a synthetic polymer with a silicon-oxygen backbone and “side chains” that are hydrogen or hydrocarbon groups.
The silicon-oxygen backbone makes silicones more stable than polymers with carbon-carbon backbones.
Silicone is durable, stable and easy to manufacture. For these reasons, it has been widely used in many daily products.
Silicones contain silicon, a naturally occurring chemical element.
The properties of silicone change with increasing degree of cross-linking. Silicone oil without cross-linking is the least rigid. Silicone resins with a high degree of cross-linking are the hardest.
