Chemistry

This page answers some basic questions around the chemistry behind silicones, and how they are made. Dig deeper into what Cyclosiloxanes are, and the different Forms of silicones in the dedicated sections. 

Where do silicones come from?

Silicones are essentially organically modified quartz. Silicon quartz consists of silicon and oxygen atoms. In the making of silicones, two oxygen atoms attached to every silicon atom have been replaced by methyl groups. 

Silicon is a chemical element widely distributed on earth in various combinations with oxygen only (silica) or oxygen and other elements (silicates). Silicon is the second most abundant element on the earth’s crust after oxygen (approximately 28% by mass) and it naturally forms long-lived, stable compounds. In many biological systems silica is an essential element of mechanical structures.

 Silicon is always found in chemically and thermally stable mineral combinations but never in its pure form. Silicon is the key to all silicone chemistry as its atomic structure dictates the properties of silicones.

 

SiO– the structure of silicon quartz

 

How is silicon obtained?

Today elemental silicon is obtained through the electro-thermic reduction of SiO2 with carbon at 1,400 degrees Celsius.

Elemental silicon is dark grey, metallic shiny, hard, and brittle. It has a melting point of 1,423°C and a boiling point of 2,630°C. Like carbon, silicon has a crystalline structure, similar to that of diamonds. Read more about the similarities and differences between silicon and carbon in our factsheet.

How are silicones made?

Obtain silicon

1400 degree Celcius reaction with carbon

Grind

Silicon metal powder

Distill

Add methylchloride

Make methylchlorosilanes

Distill

React with water and strip

Hydrolysis and stripping creates siloxanes, such as PDMS and cyclic volatile methyl siloxanes (cVMS) D4, D5 and D6

Polymerise

Mix to sealants, adhesives, elastomers

Polymerise into silicones rubber, fluids, resins and myriad other forms

A very important step in the process of creating silicones is the production of siloxanes. Siloxanes are a group of substances characterized by a chain of alternating silicon (Si) and oxygen (O) atoms. Within the group, individual siloxane substances differ in size, weight and shape. They form the backbone of silicone polymers that are used in a variety of applications such as sealants, adhesives, coatings, plastics, cosmetics, medical devices, hygiene products, food contact materials, and many other industrial applications.

Cyclosiloxanes are indispensable building blocks in the creation of many silicones. Read more about their specific chemistry, how they are regulated and how they are researched here, in the dedicated cyclosiloxanes section.

What do silicones look and feel like?

Silicones take many forms – they can be liquid, or emulsions, rubber, elastomers, resins, and much more. These different forms are the basis of literally thousands of different types of products. Hardly any industry today does not produce or use products made from one of these silicone formats.