Cosmetic Science Basics - Silicones

The vast majority of cosmetic raw materials are based on hydrocarbons. Oils, polymers, waxes and more involve bonds of carbon and hydrogen. But a notable exception to this hydrocarbon dominance is Cosmetic Silicones. Let’s review silicones used in cosmetics and why.

Silicon Molecules

Silicones are molecules or raw materials in which the primary backbone is based on a Silicon/Oxygen repeating unit. (Si-O-) In the simplest incarnation the structure is surrounded by methyl groups (CH3) and the fluid is known as Dimethicone. Chemists can vary the length of the polymer which changes the molecular weight and the fluid properties like viscosity. Hydroxyl group (OH) can also be included in the molecule to product Dimethiconol. The most common side groups include…

• methyl(CH ₃)
• phenyl(C ₆H ₅)
• allyl (-CH ₂CH=CH ₂)
• vinyl (-CH=CH ₂)
• trifluoropropyl (-CH ₂-CH ₂CF ₃)

The silicone backbone can also be twisted back on itself to produce a ring structure.  These materials, known as Cyclomethicones, are volatile and used in products in which build-up is a concern.

Why Silicones

Now that you have a sense of the silicone structure you might wonder why you would want to formulate with them. Here are the primary qualities that make silicones useful.

Slip
Silicones are incredibly slippery. When diluted onto a surface they form a film that slips past most any frictional force. So silicones on hair will make it much easier to comb. On skin, silicones make them feel smooth and soft.

Shine
Because of the even film that silicones produce, they also make a nice shiny surface. Therefore, silicones are great for creating hair shine, shiny nails, or any other application in which you want shine.

Protection
Silicones have been demonstrated to create a barrier on the surface of skin and hair. So, they are useful for products designed to protect these surfaces. Lotions, moisturizers, and long lasting color cosmetics would all benefit from the incorporation of silicones into the formulation. Hair can also be protected from heat damage and color loss.

Drawbacks

Silicones are excellent materials and you might be wondering why they haven’t replaced hydrocarbons as teh dominant ingredient. Well, as with most excellent things, there are some significant drawbacks.

Cost - Silicones cost much more than equivalent hydrocarbons. Therefore, many companies avoid them. However, you can get some of the benefit by blending them with hydrocarbons which is typically what is done.

Compatibility - Silicones are not as easy to emulsify as most oils so there can be stability and production issues. This makes them tricky to work with and reduces their use.

Consumer Concerns - While it is mostly based on misinformation, many consumers believe silicones build-up on hair or leave a layer of damaging wax. So, if you are creating formulations for this type of consumer, silicones will just not do.

Overall, silicones are great materials for cosmetic chemists and you should experiment with them in most any formulation you work on. But be aware that they will not work for every application and some consumers just don’t want to see them on the label.