EDITOR’S NOTE: There has been a lot of discussion in the hair care industry about silicones recently, and, frankly speaking, including plenty of misinformation. Silicones have been broadly and safely used in hair care products for over 50 years. There are many beneficial reasons why silicones are used: they coat and protect hair, are inert and have an excellent safety and ecological profile. After all, almost all silicones are derived from one of the most common natural materials on planet earth—silica—otherwise known as sand. As the authors of Healthy Hair explain, “most manufacturers now employ silicones into conditioners as they protect the hair cuticle.”[i] Nevertheless, it is important to choose the appropriate silicones and incorporate them in precise proportions to any product to get the desired effect. Desert Botanicals’ R&D team has significant expertise in identifying and selecting the best and highest quality silicones to use in our products. Namely, choosing a mixture of silicones that protect the cuticle without building-up on the hair shaft or weighing hair down. As a result, we asked our R&D team to write a blog that explains some of the science, applications, and safety behind silicone technology.
Introduction
Silicone-based ingredients used in hair care products are synthetically derived allowing manufacturers to make almost limitless variations to their basic chemical structure. Modifications such as changing the size of the polymer or adding other functional groups to the basic framework creates a wide diversity of potential physical properties and performance characteristics. For example, these differences can vary from products that are liquids and very easy to pour to thick gums or even solids. In addition, combining different groups to the polymer framework allows the manufacturer to vary the relative solubility of the raw materials in water from completely insoluble to dispersible to completely soluble. Obtaining the desired effect in our hair care products requires an extremely delicate balance of these and other variables.
Dimethylsiloxane – The Basic Structure
The basic structure for silicone polymers is a dimethylsiloxane building block (see structure below). These building blocks can be made in straight chains or in cyclic structures. This is described in some examples below. The diversity of materials available to the formulator of hair products are based on the other groups that can be bonded to this basic building block unit.
Changing the size (molecular weight) of the molecule not only changes the flow (viscosity) characteristics of the product but also the volatility (ease of evaporation). Small and low molecular weight compounds have very low viscosity and spread readily throughout the hair. Because their surface friction and surface energy are low they provide easy combing and detangling characteristics that are commonly attributed to silicones. In addition, their inherent properties make hair feel smooth and soft, restore shine, and can strengthen damaged hair. One added benefit to these low molecular weight compounds is that they can solubilize the higher molecular weight viscous gums making them easy to distribute evenly throughout the hair.
Silicones are stable and inert. Dimethylsiloxane polymers (like dimethicone) at any molecular weight are not soluble in water. However, even though they are not soluble in water they are very permeable (breathable) to water vapor (moisture). That is why they are used extensively in wound care products to protect damaged skin. Making silicone polymers with other functional groups, like polyethylene oxide (PEO) or polyethylene glycol (PEG), can change the properties of silicone from insoluble to fully dispersible and/or fully soluble in water depending on how many hydrophilic (water loving) groups are added. Adding phenyl groups increases the refractive index of the molecule and improves shine. Adding amine or quaternized nitrogen groups help bond and protect areas of damaged hair and reduce static improving manageability. Lastly, many of basic ingredients used to make personal care products also contain surfactants, lubricants, emollients, etc. that stabilize the raw material and provide additional properties useful to formulators.
Dimethicone – Great for Coating the Cuticle
Dimethicone (see below) is one example of a straight chain polymer that is widely used in hair care products. You will find this material or similarly structured compounds in the ingredients list found on the containers of many conditioners, hair serums, and shampoos.
Many different products can be made by changing the degree of polymerization (changing “n” in the picture above) of dimethicone giving a wide range of materials with vastly different chemical and physical properties. These effect not only how the product feels in your hair (for example giving a silky, soft, and/or smooth feel) but also affects other properties like the improving shine, texture and manageability of hair. Dimethicone is very hydrophobic (repels water) and non-polar. It has a very low surface tension and coefficient of friction. These properties make wet and dry combing easier, improve manageability, curl retention, and frizz volume control. Small low viscosity products that can improve lubrication (ease of combing) to the product. Medium viscosity products are designed to provide a smooth and silky feel to the hair. Large dimethicone polymers are high viscosity oils and gums that coat hair cuticle when properly dispersed. Silicone polymers have low thermal conductivity thereby providing protection against high heat hair blowers and heated styling tools. Moreover, their structure supports hair and helps prevent breakage. Even though these materials are not soluble in water they are readily removed during washings, especially with a high-quality clarifying shampoo.
Cyclomethicone – For Even Distribution
Cyclomethicone (dimethylcyclopentasiloxane (D5) -see picture below) is a second commonly used silicone with the same basic building blocks but in this case the structure is cyclic.
D5 is used both as a solvent and diluent to help dissolve highly polymerized dimethicones (and similar molecules) allowing these large molecules to be evenly distributed throughout hair in both leave-in and rinse-out conditioners. This compound gives hair a light and smooth texture when applied and gives a temporary emolliency with a non-greasy feel. The reason the feel is temporary is because the product has a low boiling point it will evaporate (volatilize) from hair over time lowering the overall amount of siloxane remaining in the hair.
Some siloxanes are made in combination with a non-ionic surfactants making emulsions. Depending on the chemical nature of the surfactant used water dispersibility/solubility can be adjusted from non-soluble to fully soluble. These emulsions are commonly used in emulsifying creams and silicone gels and improve the feel of use in shampoos and provide the silky feeling to the cosmetics.
Conclusion
Healthy hair is naturally hydrophobic. Silicone additives are thermally stable and restore the natural hydrophobic state of hair that is often lost due to chemical and thermal treatments combined with mechanical and UV damage. They protect the hair shaft from breakage by forming a very thin film layer mimicking the naturally hydrophobic lipid layer on the cuticle that is often stripped away by today’s harsh thermal and chemical treatments. Silicones spread easily on hair forming a protective film that prevents water loss caused by drying or heated styling tools. However, too much of anything is not a good thing. Several recently publicized cases of other companies’ hair care products that are purported to cause hair loss and breakage and/or scalp irritation have been reported specifically noting some harsh ingredients used to make the formulation. At Desert Botanicals we take great care in selecting and balancing state-of-the-art silicones for optimal performance. These ingredients have a long history of safe and effective use. We have spent years researching the interaction of a wide variety or silicones by themselves and in combination with other ingredients to engineer the right balance of properties from the ingredients selected. We have discovered the key to achieving ideal performance is a delicate balance between the ratio of low molecular weight volatile silicones with the right proportion of higher refractive index and higher molecular weight silicones. This combination of silicones gives the hair shine and featherweight manageability and while protecting hair cuticle from heat and chemical damage. We have also learned that purified natural oils and aloe in combination with vitamins and anti-oxidants coat and protect the hair cuticle while adding needed nutrition. Desert Botanicals has performed extensive research and exhaustive experimentation to provide you with products that will get your hair noticed without using harsh chemicals that can damage your hair or irritate your scalp.
[i] Marsh J, Gray J, Tosti A. Healthy Hair. 1st ed. Springer Publishing; 2015, p. 72.
