Silicones
Introduction
Silicones, also known as polysiloxanes, are polymers that include any synthetic compound made up of repeating units of siloxane, a chain of alternating silicon atoms and oxygen atoms, combined with carbon, hydrogen, and sometimes other elements. They are typically heat-resistant and rubber-like, and are used in sealants, adhesives, lubricants, medicine, cooking utensils, and thermal and electrical insulation. Some common forms include silicone oil, silicone grease, silicone rubber, silicone resin, and silicone caulk.
History
The development of silicone polymers began in the early 20th century with Friedrich Bergius's attempts to synthesize silicon carbide. A series of discoveries and innovations by scientists such as Frederick Kipping, Eugene Rochow, and James Wright led to the commercial production of silicones by companies like Dow Corning and General Electric.
Chemistry
Silicones are made of siloxane monomers, which are in turn made of silicon, oxygen, carbon, and hydrogen atoms. The silicon atoms in these monomers are tetravalent, meaning they form four bonds with other atoms. In the case of silicones, these bonds are typically with oxygen, carbon, and hydrogen atoms. The unique properties of silicones, such as their flexibility, heat resistance, and low toxicity, are largely due to the characteristics of these siloxane monomers.
Types of Silicones
There are several types of silicones, each with its own unique properties and applications. These include silicone oils, silicone greases, silicone rubbers, silicone resins, and silicone caulks. Silicone oils are primarily used as lubricants and hydraulic fluids, while silicone greases are used in a variety of applications, including electrical insulation and as a release agent in cooking and baking. Silicone rubbers are used in a wide range of products, from kitchen utensils to medical devices, due to their flexibility and heat resistance. Silicone resins are used in coatings and sealants, and silicone caulks are used in construction and home repair for their adhesive properties and resistance to moisture.
Applications
Silicones are used in a wide variety of applications due to their unique properties. They are used in the automotive industry for gaskets, seals, and lubricants. In the construction industry, they are used for sealants, adhesives, and coatings. In the electronics industry, they are used for insulation, encapsulation, and thermal management. In the medical field, they are used for implants, tubing, and a variety of other medical devices. They are also used in personal care products, such as hair conditioners, skin care products, and antiperspirants.
Environmental Impact
While silicones are generally considered to be environmentally friendly due to their low toxicity and ability to be recycled, there are some concerns about their potential environmental impact. Some studies have suggested that certain types of silicones may be harmful to aquatic life, and there are ongoing debates about the biodegradability of silicones. However, the overall consensus is that silicones are safe for the environment when used responsibly.