Silicone Chemistry

Silicone Chemistry

The common building blocks used to manufacture silicone polymers are known as cyclosiloxanes and linear siloxanes.  These substances share a common chemistry, but each substance is different with regard to its specific properties and uses. The most common of these silicone substances in commercial use are known as D4, D5, D6, L2, L3, L4, and L5.


Cyclosiloxanes are used in the manufacture of silicones, in combination or alone in personal care products, and as carriers, lubricants and solvents in a variety of commercial applications. Data generated from these studies support their safety and demonstrate that the products in which they are a component are safe when used as intended.


Octamethylcyclotetrasiloxane (D4) is an odorless, colorless non-oily volatile silicone fluid used primarily to make other silicone materials. During this process, virtually all of the material is consumed, with only a tiny amount of D4 remaining. Additionally, D4 is a critical substance for electronic component manufacturing.


Decamethylcyclopentasiloxane (D5) also is an odorless, colorless non-oily volatile siloxane fluid used primarily to make other silicone materials. It is used as an ingredient in personal care and consumer products and in dry cleaning. In personal care products, D5 acts as a “carrier,” allowing products to spread smoothly and easily, providing a silky, luxurious feel during application. In dry cleaning, D5 carries detergent to clothes and rinses away suspended dirt and oils trapped by the detergent. It does not interact with textiles and therefore helps maintain the quality and color of clothes that are dry cleaned.


D6 is an odorless, colorless liquid mostly used as an intermediate or basic raw material in the production silicone rubbers, gels and resins. D6 can also be used as an ingredient in silicone mixtures used in cosmetic applications such as skin creams and deodorants.

Linear and Siloxanes

Linear Siloxanes are primarily used in cosmetics, electronics, medical devices, adhesives and sealants, as well as in industrial applications such as paints and coatings. Independent scientific studies, voluntary industry stewardship efforts, and regulatory evaluations have all demonstrated the safety of L2, L3, L4, and L5. No jurisdiction in the world has imposed any regulation or restriction on linear siloxanes in their intended applications.


Hexamethyldisiloxane (L2) is a colorless liquid and used in liquid bandages to protect damaged skin from irritation from other body fluids.  It is also used in applications for the semiconductor industry.


Octamethyltrisiloxane (L3) is a clear, transparent viscous liquid and is used in adhesives and conductive materials.  It is also used in the cosmetics and apparel industries.


Decamethyltetrasiloxane (L4) is a colorless liquid that is used as an intermediate in the manufacture of other chemical compounds and in cleaning products. It is also used in colorants and in personal care products.


Dodecamethylpentasiloxane (L5) is a colorless liquid and is used to make silicone oils and as a petroleum lubricating oil ingredient.

These substances are basic members of the silicone family, serving as the building blocks for many silicones. They are used to create a diverse range of silicone materials, called polymers that provide beneficial characteristics to a wide variety of applications and products. The linear and cyclic siloxanes are most frequently used as raw materials, meaning that the substances are employed in the manufacturing process but are only present at very low levels in the final products.