Silicone Alternatives In Personal Care

Under the general name of “silicone” exists a family of synthetic oils that have different chemical structures and accordingly possess diverse properties. For example, volatile silicones are known to bring a light and smooth feeling to cosmetic formulations, while high molecular silicone grades and silicone derivatives are usually included in hair care formulations for conditioning, shine or even strengthening effects. But in January 2009, the Canadian Environmental Protection concluded that siloxanes D4 and D5 are not a concern for human health but that they are harmful for the environment.1 The EU commission is currently evaluating D4 and D5 silicones for final PBT (Persistent, Bioaccumulative and Toxic) classification. If they are classified as PBTs, they may be banned for use in personal care products under the REACH regulation within the EU.2 At the same time, more consumers are aware of the impact that products can have on the environment, and are looking for personal care ingredients that serve as silicone alternatives.

Fig.1: In a climate room, 4 mg of emollient is applied to the test person’s inner forearms which have been lightly cleaned with cotton wool and ethanol; transparent paper is then pressed onto the area 10 minutes after application, and the resulted surface area is determined in mm²/10 min

These important market developments are already anticipated by many finished goods producers. The number of products launched claiming to be “silicone-free” has increased dramatically in the past three years, for instance with more than 300 product launches in Europe in 2009.3 To serve this growing demand, manufacturers are striving to enhance their raw material portfolio. Cognis’ researchers support them in seeking innovative ingredients that work as silicone alternatives. This article presents solutions for silicone-free hair and skin care formulations.

A Pleasant Skin Feel
In order to bring the same lightness as cyclic silicone in leave-on products, short chain esters, carbonates or ethers with a high spreading value can be used. The spreadability of an emollient is a decisive factor for the sensory properties of an emulsion.4 In addition, fast spreading emollients help the emulsion to spread homogeneously and uniformly on the skin to evenly distribute active ingredients.

Zeidler describes a classification system for cosmetic emollients based on their slow, medium or fast spreading behavior on the skin.4 The method used to determine the spreadability is shown in Fig. 1. If a cosmetic emulsion is formulated exclusively on the basis of fast spreading emollients, the desired smooth, silky skin sensation fades away very quickly, and it is replaced shortly after by a waxy sensation on the skin which relates to the amount of non-spreading substances; e.g., consistency waxes or emulsifiers that are present.4 In contrast, slow spreading emollients (e.g., vegetable oils) give a less remarkable sensation of smoothness, which remains virtually unchanged over time. Ideally, slow oils are combined with fast and medium spreading emollients to give a “spreading cascade,” avoiding gaps in the imparted sensation of smoothness.

One of the first light emollients in the market, dicaprylyl ether (Cetiol OE, Cognis), combines a very high spreadability (1 600 mm²/10 min) with good stability. This fully vegetable derived ingredient is hydrolysis stable, suitable for formulations with a wide pH range, and especially relevant for AP/deo applications.

Another example is dicaprylyl carbonate (Cetiol CC, Cognis), a fast-spreading dry emollient (1 600 mm²/10 min), which can significantly improve the sensory performance of the final formulation. It is highly compatible with many different skin types and easy to emulsify. Its good ability to dissolve crystalline UV filters and to disperse pigments makes it particularly suitable for sun care and decorative products. Additionally, it balances the impact of oily and slow spreading UV-filters on the skin feel.

With the right emollient, consumers can take care of their skin and truly enjoy an inspiring and satisfying experience at the same time.5 Propylheptyl caprylate (Cetiol SenSoft, Cognis) was developed to serve this trend. Sensory assessments have shown that this emollient has multi-dimensional softness and leaves a silky and velvety feel on the skin. It also has a very high spreading value of 1 900 mm²/10 min.

New coco-caprylate (Cetiol C5, Cognis) is a readily biodegradable light emollient recommended for use in BDIH and NaTrue-compliant as well as traditional formulations. The Ecocert-approved ingredient is derived from 100% natural, renewable feedstocks and has a spreadability of 1,300 mm2/10 minutes. Sensory assessments done by trained panelists have proven that the sensorial profile of this emollient comes very close to the ones of cyclomethicone—it provides the formulation a pleasant and light skin feel (see formula above and Fig. 3 on p. 70). Compared to cyclic siloxanes and alkane alternatives, it is easy to emulsify, has medium polarity and a high flash point (over 140°C). This makes it ideal for facial, body, sun and hair care products as well as decorative cosmetics.

Fig. 2: Moisturizing day cream formulation based on Cetiol C5

Sensory modifiers and smoothing agents can also improve the velvety skin feeling of a leave-on product. Used in addition to the right emollient, they can enhance the final sensorial experience. Cosmedia Gel CC (INCI: Dicaprylyl carbonate (and) stearalkonium hectorite (and) propylene carbonate), for instance, is a new version of a hectorite dispersion. The organo-clay platelets impart lubricity by reducing stickiness. It is used as a texture agent and creates a very homogeneous film on the skin providing a melting texture with a velvety matte finish. It also helps to stabilize the emulsion and to suspend actives in AP/deo and pigments in foundation applications.

High Performance Hair Care
Silicones are widely used in shampoos and conditioners because of their well-known conditioning properties. Consumers are looking for silicone-free solutions, but they demand additional benefits to cleansing properties from today’s shampoo: whether they come in a clear or opaque formulation, shampoos must provide superior conditioning, as well as a perceivable repair effect, anti-hair breakage protection or even gloss enhancement.

To achieve a strong conditioning effect in combination with anti-breakage, a micronized wax dispersion of PEG-4 distearyl ether (and) sodium laureth sulfate (and) distearyl ether (and) dicaprylyl ether (Lamesoft Care, Cognis) was developed. The formula, which has been patented for silicone-free systems, shows excellent anti-breakage results in a shampoo, which is normally only achieved with conditioners: physical measurements on treated hair strands have demonstrated that a shampoo containing only 3% of the dispersion delivers the same outstanding anti-hair breakage protection as three leading benchmark silicone-based shampoos used in combination with their conditioner (see Fig. 4). It achieves particularly strong conditioning effects in combination with cationic polymers.6 As an added formulating benefit, shampoos that contain silicone dispersions require a polymer for stabilization, whereas those containing waxes do not. Performance tests also prove that shampoo formulations containing this dispersion improve the hair shine as well.

Fig. 3: Sensory assessment have proven that the sensorial profile of a Cetiol C5-based formulation comes very close to the ones of a benchmark formulation containing silicones.

For manufacturers seeking solutions that are easy to incorporate into clear shampoo formulations, microemulsion dicaprylyl ether (and) decyl glucoside (and) glyceryl oleate) (Plantasil Micro, Cognis) was developed. It is a transparent Ecocert-, BDIH-, NaTrue- and NPA-approved microemulsion made entirely from natural, renewable sources. It is easier to formulate than silicones and enables formulators to achieve good conditioning performance in silicone-free shampoos. This optimized blended surfactant-oil system synergistically improves the conditioning performance of shampoos when it is combined with cationic polymers—a combination that opens up new possibilities in shampoos. During the dilution of shampoos, gel-like particles are formed. The gel phase is created by phase transition during application through the dilution process. This in turn generates the hair conditioning effect.7 Microemulsions enhance this phenomenon as more microemulsion added in a shampoo causes a more pronounced phase separation with more gel phase resulting in better conditioning performance. With a nano-sized structure and an average particle size of less than 100nm, this microemulsion enables high amounts of oil to be incorporated into cosmetic formulations without affecting their transparency.

Fig. 4: A shampoo containing only 3% of Lamesoft Care delivers the same outstanding anti-hair breakage protection than three leading benchmark silicone-based shampoos used in combination with their conditioner.

Some silicone oils mainly used in shampoos and conditioners are able to create a homogenous film on the hair, and suppliers claim it as hair strengthening or protection. A high-performance ingredient to protect, repair and restructure the hair is the microprotein Gluadin WLM Benz (INCI: Hydrolyzed wheat protein). This wheat-based protein active has a very low molecular weight, which helps to ensure a deep penetration into the hair fiber. This provides an effective strengthening from within, and helps to reduce hair breakage by around 80%. It also creates a protective shield on the cuticle, making hair perceptibly smoother, and contributes to a more pleasant care experience with wet and dry hair.

Cationic Rheology Modifier
Rheology modifiers bring the final texture to a personal care formulation. Even if emollients bring the major sensorial properties to a formulation, every ingredient can have an influence on the overall feeling. These details make the difference between standard and premium products.

One such rheology modifier is Cosmedia Triple C (INCI: Polyquaternium-37 (and) dicaprylyl carbonate (and) lauryl glucoside), a liquid dispersion polymer specifically designed for hair conditioners and skin care formulations. It consists of an efficient cationic inverse emulsion polymer, a high-grade cosmetic emollient and an EO-free emulsifier as an activating agent. The polymer’s cationic charge and the spreadability of the emollient provide a perceivable improvement of the sensory profile of skin and hair care products, while its pseudoplastic flow behavior makes formulations containing this additive very easy for consumers to apply. Furthermore, it measurably improves the combability of both wet and dry hair, is readily activated in cold water, and is effective over a wide pH range. In comparison with conventional cationic inverse emulsion polymers, this additive is more tolerant toward electrolytes, and has superior viscosity behavior in hair and skin care products.

Leveraging the Green Trend
Over the years, ingredients such as silicones have proven their performance and are still very popular, but more consumers follow the global green trend and are aware of the impact the products they buy have on their personal wellbeing and the environment. As such, they want personal care products based on alternative ingredients that are as green as possible, but they are not willing to sacrifice product performance or convenience.

Manufacturers must consider performance factors such as spreadability, sensorial properties and conditioning properties. For example, nature-based emollients or microemulsions with sustainability benefits provide performance similar to that of conventional ingredients. With the right alternative ingredient, manufacturers can develop products that meet consumer demands for convenience, sustainability and an overall experience of care and comfort.

References
1. Environment Canada and Health Canada. Proposed Risk Management Approach for Cyclotetrasiloxane, cotamethyl- (D4) and Cyclopentasiloxane, decamethyl- (D5). Jan 2009, http://www.ec.gc.ca/substances/ese/eng/challenge/batch2/batch2_541-02-6_rm.cfm
2. European Commission. Regulation (EC) 1272/2008, Annex VI, Table 3.2. Sept. 2009. http://ecb.jrc.ec.europa.eu/classification-labelling
3. URL: http://www.GNPD.com
4. Über das Spreiten von Lipiden auf der Haut, U. Zeidler, Fette Seifen Anstrichmittel, Vol. 87, Nr. 10, 1985, S. 403–408
5. High-performance emollients with sensory appeal, U. Issberner, Cossma, Sept. 2009, p 20-22
6. A micro-wax dispersion to condition hair and reduce breakage, H.-M. Haake, W. Siepel, S. Cornelsen, Cosmetic & Toiletries, Vol. 124, No.11, p 46-52, Nov. 2009
7. A ‘Green’ Microemulsion for Improved Conditioning Performance of Shampoos, M. Hloucha, H.-M. Haake, G. Pellón, Cosmetic & Toiletries, Vol. 124, No. 5, May 2009