Despite the weight of safety concerns and controversy, silicones have long held a pervasive stronghold in cosmetic formulations. Organic and alternative solutions are on the rise, however. Cosmetics & Toiletries spoke with Tony O’Lenick, co-founder and president of Siltech LLC, on the function and future of silicones in cosmetics.
C&T: What are "silicones?”
Tony O’Lenick: Silicones are a diverse class of compounds that have an Si-O-Si bond present. They include:
- Silicone homopolymers, a class which has only silicon, oxygen and methyl groups present in the polymer. This group includes fluids that are linear polydimethyl siloxanes, high molecular weight linear polymers called gums, and branched polymers referred to as elastomers or resins.
- Organofunctional silicone polymers, which include many other types of groups including higher alkyl (having improved oil solubility), PEG/PPG groups (having improved water solubility), fluoro groups (having improved fluoro solubility) and mixtures of these groups on the same backbone.
If a personal care formulation is compared to a gourmet meal, the silicone will be the spice and not the meat or potatoes.
C&T: Which ones have stirred up controversy, and why?
TO: First and foremost, the silicones that have stirred up controversy are the volatile cyclic polymers most commonly called cyclodimethicone (principally D4); D4 is generally not used in our industry.
“[In] January 2009, Environment Canada and Health Canada proposed to add D4 and D5 siloxanes to the List of Toxic Substances pursuant to the Canadian Environmental Protection Act, 1999 (CEPA), and to develop regulations 'to limit the quantity or concentration of D4 and D5 in certain personal care products.'
In addition, under CEPA, anyone proposing a "significant new activity" involving siloxanes must notify the Minister of the Environment. However, there are currently no restrictions on these ingredients in cosmetics." [According to the David Suzuki Foundation.]
A second concern is that despite the fact the raw material used to make silicone polymers (SiO2) makes up 25% of the Earth’s crust SiO2, silicone polymers are not considered green. In fact, they are not renewable—but they are quite abundant.
C&T: Are these specific to cosmetics/personal care?
TO: These materials are used in other industries, but are not normally applied topically in other industries, so added concern is warranted.
C&T: In your opinion, as a silicones expert, should consumers be concerned about them? Why or why not?
TO: One class of materials of concern in our industry is cyclomethicone compounds and specifically D4. Cyclomethicones have a dry feel on the skin, and are sometimes used in antiperspirants. This, I believe, is not a good use of these materials as the percentage is generally quite high (around 20%). D4 simply should not be used in our industry; other silicone polymers are far less problematic and of much greater interest to our industry.
It is my opinion that silicone polymers, when properly formulated into personal care products, represent no health hazard and are safe from that standpoint. However, a properly formulated product should have silicones added only to provide properties that are not achievable by using other materials. I have often said that if a personal care formulation is compared to a gourmet meal, the silicone will be the spice and not the meat or potatoes.
I would avoid using cyclomethicones as solvents in personal care formulations. They are commonly used as a solvent for elastomers, gums and other materials. Simply put, there are better ways to achieve this effect, most of which make use of predominately organic ester, with a proper silicone added. Organic solvents alone simply will not provide the required surface tension (25 dynes/cm), lack of volatility and skin feel that can be provided with the properly organic silicone blend.
A properly formulated product should have silicones added only to provide properties that are not achievable by using other materials.
C&T: What sorts of alternatives are being offered? How do they compare?
TO: Silicone polymers are already on the market that have been engineered to provide the required properties of surface tension reduction, feel modification, emulsification, wetting and film formation in specific applications, where the silicone component is the lower concentration in the raw material and organic compounds are the predominant material. If properly selected, they work very well. However, there is no one polymer that functions to provide all the desirable properties of silicone in formulation, just like there is no one universal surfactant or natural oil for all applications.
C&T: Do you think silicones will be phased out or reinvented? If the latter, how?
TO: The old fashioned silicone compounds like cyclomethicone and silicone fluids will be used less and less, being replaced by engineered polymers that provide specific benefits in formulations.
The formulator needs to always ask two questions: Why use silicone in the formulation, and am I using the most efficient silicone to deliver the desired effect in my formulation, interacting synergistically with the other ingredients in my formula?