Silicone is a versatile polymer used in elastomers, oils, greases and caulks, among other materials. Its primary ingredient is silica — one of the most commonly occurring forms of sand. Here’s what you need to know about silicone production.
Silica, Silicon and Silicone
One important distinction when talking about the production of silicone is that between silicone and silicon. Silicon — with no “e” — is a chemical element (Si). Like most elements, it is not naturally found in its isolated form. Silicone, however, refers to a broad class of polymers that consist of a siloxane bond (chemical formula -Si-O-Si-) with various organic compounds attached.
A Step-by-Step Guide to the Production of Silicone
Isolating silicon from silica is the first step in the production of silicone. This is done by heating a large volume of quartz sand to temperatures as high as 1800˚C. The result is pure, isolated silicon, which is allowed to cool and then ground into a fine powder.
To make silicone, this fine silicon powder is combined with methyl chloride and heated once again. The heat triggers a reaction between the two components, forming what is known as methyl chlorosilane. Methyl chlorosilane is actually a mix containing several compounds, the most predominant of which, dimethyldichlorosilane, is the main building block of silicone.
Getting from dimethyldichlorosilane to silicone requires a complex distillation process in which the various components of the methyl chlorosilane are separated from one another. Because different chlorosilanes have different boiling points, this can be done by heating the mixture to a series of precise temperatures.
After distillation, water is added to dimethyldichlorosilane, which causes it to separate into disilanol and hydrochloric acid. The hydrochloric acid then acts as a catalyst for the disilanol, causing it to condense into polydimethylsiloxane.
Polydimethylsiloxane, as you’ll notice, contains the siloxane bond, which is the backbone of silicone. From there, silicone is polymerized using a variety of methods depending on the desired properties of the end product.
While the production of silicone may seem complex, in reality it’s fairly straightforward and can be done on a mass scale for a relatively low cost. As such, it’s little wonder that versatile silicone has emerged as one of the most popular elastomers for commercial and industrial use.