Spotlight on silicone alternatives

John Woodruff analyses the backlash against silicones and asks, what are the alternatives?

When over an extended period of time silicones have established their versatility, safety and usefulness in cosmetics, why now is there a backlash against them?

The issue

Much of it is because of internet misinformation, which blames silicones in personal care for every misfortune possible, from causing acne to being toxic to the user. The other problem, also widely reported on the internet, is concern about the environment. These issues are discussed at length by the Global Silicones Council, a not-for-profit, international organisation whose stated mission it is to promote the safe use and prudent product stewardship of silicones worldwide. It is comprised of the Silicones Environmental, Health and Safety Council of North America (SEHSC), Centre Européen des Silicones (CES) in Europe and the Silicone Industry Association of Japan (SIAJ), and further information is available on its website www.siliconesinfo.com.

The Global Silicones Council reports that silicones are among the most extensively studied materials in consumer and industrial use today. More than 1,000 studies have been conducted to assess the safety of silicones for workers, consumers, the environment and manufacturing processes. The results of this continued research and testing demonstrate the safety of silicones in diverse and important applications when used properly.

The cosmetics industry relies heavily on safety assessments by the Cosmetics Ingredient Review [CIR] panel of experts, which, in a 78-page report published in 2011, concluded that cyclomethicone, cyclotetrasiloxane, cyclopentasiloxane, cyclohexasiloxane and cycloheptasiloxane are safe as cosmetic ingredients in the practices of use and concentration as described in this safety assessment. The safety of numerous other silicones has been examined by the CIR, including dimethicone, amodimethicone, various alkyl methicones and silicone esters, and all were found safe as used in cosmetic products in a report dated 2003.

In Europe, the Scientific Committee on Consumer Safety (SCCS) performs a similar function to the CIR and in 2010 it published the opinion that cyclomethicone (D4 and D5) does not pose a risk for human health when used in cosmetic products. Despite the detailed examinations described by the CIR, Environment Canada cast doubts on their safety by suggesting that D4 and D5 may pose a risk to humans and to the environment. However, in late October 2011, the Canadian Board of Review released the following statement: “The Board conducted a scientifically rigorous review of all the relevant scientific information related to our mandate. Taking into account that information, the Board has concluded that Siloxane D5 does not pose a danger to the environment or its biological diversity. Furthermore, the Board concluded that, based on the information presented, Siloxane D5 will not pose a danger to the environment or its biological diversity in the future.”

In England and Wales, the Environment Agency has published an intention to file a restriction order, which has been added to ECHA’s registry of current restriction intentions. It reads: “The siloxanes octamethylcyclotetrasiloxane (D4) and decamethylcyclopentasiloxane (D5), used in the personal care industry, have been proposed by the UK, which expects to submit the intention on 16 January 2015.” The restriction concerns their use in wash-off personal care products and states that these must not contain more than 0.1% of D4, or more than 0.1% of D5, in the EU.

In fact, D4 has largely been phased out of cosmetic use, so if this restriction order is activated it is D5 for which a replacement is required. Siltech’s O’Lenick summarised the attributes that would require consideration for a satisfactory alternative as viscosity, surface tension reduction, flammability, its effects on skin and its cost. A major attraction of D5 is the way it imparts a dry skin feel. This is not due to its volatility, which is negligible at skin temperatures, but to its low surface tension[1]. A similar effect can be obtained by mixing alkyl silicones with natural oils: for example, behenyl dimethicone is soluble in soybean oil and reaches a critical micelle concentration at about 4%, at which point it gels the oil. This gel has a low surface tension and imparts a dry skin feel while dramatically reducing the silicone content of the oil phase.

The alternatives

Until the controversy over cyclomethicones began, they were often used as solvents and carriers for high molecular weight dimethicone and dimethiconal. Various alternatives are now being suggested; Wacker launched Belsil GB2050 in October 2014, which is a mixture of dimethicone and dimethiconol with a Brookfield viscosity of 8,000-10,000 mPa*s that can be readily diluted with cyclopentasiloxane, disiloxane, C9-13 isoparaffin and low viscosity dimethicones. Primarily for use in hair conditioning products, it is also finding application in skin care and colour cosmetics. Disiloxane is available from Wacker as Belsil DM 0.65 and is a suitable substitute for D5 in most applications. Wacker has also produced a D5-free w/si emulsifier blend trade-named Belsil WO5000 [INCI: Dimethicone, caprylyl dimethicone ethoxyglucoside] that is non-ionic, mild and gentle, and shows excellent solubility in all kinds of silicone oils. It is said to be suitable for fluid emulsions with good pigment dispersion, imparting an extremely soft, smooth, velvet skin feel. Biosynthis combines coconut alkanes with dimethiconol as Vegelite Si-1517, a silicone gum without D5.

Gosulin IL from Gova is manufactured from sugar and coconut oil, and boasts similar characteristics to cyclomethicone D5

To avoid silicones altogether it is necessary to look at some of the very light esters available such as Crodamol SFX [INCI: PPG-3 benzyl ether ethylhexanoate] from Croda. It is said to disperse mica, reduce tack and impart slip and lubricity to hair fibres with a similar sensory profile to D5, and to be better than D5 as a solvent for organic sunscreens. In tests, all nine of its rub-out sensory attributes were statistically similar to D5. Also from Croda, Crodamol STS [INCI: PPG-3 benzyl ether myristate] is offered as a multifunctional alternative to silicone with similar characteristics such as feel and shine boosting benefits. It is easily emulsified, reduces tack of other emollients and has good pigment wetting properties. The third emollient from Croda to be offered as an alternative to silicones is Arlamol LST [INCI: PPG-3 isostearyl methyl ether]. It has good pigment wetting properties, spreads over the skin quickly to provide a light, dry skin feel and is particularly recommended for make-up applications.

The LexFeel N Series from Inolex is a range of 100% natural and sustainable emollients that have the sensory feel of cyclomethicone and dimethicone. They are ‘ecocertified’ and readily biodegradable and offered as alternatives to silicone fluids for improving skin feel and for enhancing shine and texture in hair care products. All six materials in the LexFeel N range are based on combinations of diheptyl succinate and capryloyl glycerin/sebacic acid copolymer of varying ratios and they can be substituted for D5 and for dimethicones of viscosities ranging from 5cs to 360cs. Other materials from Inolex include LexFeel Shine [INCI: Propylene glycol dibenzoate], which is suggested as a substitute for phenyl trimethicone. LexFeel Natural [INCI: Heptyl undecylenate] derived from castor oil is an extremely light and dry emollient suitable for natural products and LexFeel 700 [INCI: Polyester-4] is an emollient, humectant, pigment dispersant and dye solubiliser used in lipstick, lip gloss and other colour cosmetics.

Alternatives to esters are hydrocarbons and hydrogenated hydrocarbons: Smart5 from IMCD was engineered to be as close as possible to volatile D5 and is offered as a direct replacement. It is said to be perfect for make-up, as well as providing a very elegant feel on skin and hair, and water resistance in sun care. It evaporates in a similar way to volatile silicones and is a combination of isododecane with hydrogenated tetradecenyl/methylpentadecene. The Dedraflow range from The Innovation Company offers five volatile grades based on mixtures of hydrogenated polyisobutene with other hydrogenated hydrocarbons. They have been designed to replace cyclomethicone and have the same skin feel and a similar volatility profile, and can be used to replace cyclomethicone without further modification to the formulation while delivering the same feel and performance as before.

Dr. Straetmans offers three materials of low viscosity with good spreading properties, pleasant skin feel and excellent skin compatibility. Dermofeel MCT [INCI: Tricaprylin] can be incorporated as an oil component in natural cosmetic formulations due to its pleasant silicone-like skin feel and fast absorption. Dermofeel BGC [INCI: Butylene glycol dicaprylate/dicaprate] is for use in baby care, decorative and sun care cosmetics, especially those with a high SPF as it is a very good solvent for UV filters. Also a good solvent for UV filters is Dermofeel TC-7 [INCI: Triheptanoin], which is a non-greasy oil component of natural origin used in w/o and o/w emulsions.

There are materials from natural sources that are offered as silicone alternatives. One such is Gosulin IL from Gova. It is a mixture of isoamyl laurate and isoamyl cocoate manufactured from sugar and coconut oil that has a very low viscosity and very similar characteristics to D5. It is miscible with dimethicone and improves the application characteristics of emulsions with high oil and wax content, and body butters. It is also said to be a good pigment dispersant, including for micronised titanium dioxide, and is a solvent for organic sunscreens, making it of particular interest for high SPF sun care products. Isoamyl laurate is supplied by Dr. Straetmans as Dermofeel Sensolv and is also recommended for sun care products because of its pigment dispersing properties allied to its good solvent characteristics.

Alban Muller has Lipolami [INCI: Silybum marianum ethyl ester], which has a light silicone-like touch and contains over 50% linoleic acid, the most important of the omega-6 family of essential fatty acids. It has an extremely low surface tension, which ensures rapid spreading, small droplet size in emulsions and good pigment wetting and dispersing properties. Stéarinerie Dubois claims that Dub Zenoat [INCI: Propanediol dicaprylate] can be positioned as a natural alternative to cyclomethicones due to its similar sensory profile and it can also be used as a substitute for synthetic ingredients like dicaprylyl carbonate and isohexadecane. It is an excellent solubiliser for organic sunscreeens and dispersing aid for pigments, which makes it useful in formulations for sun care, make-up and skin care.

Biosynthis offers Vegelight 1214 Fluid [INCI: Coconut alkanes] as an Ecocert-certified alternative to D5 with a very similar viscosity and refractive index and nearly identical sensorial properties. Biosynthis also combines coconut alkanes with dilinoleic acid/propanediol copolymer as Viscoplastic Green 350 HVL offered an additive for creams and lotions and with dimethicone/vinyldimethicone crosspolymer as Vegelights Si 113 and 146, which have a long lasting powdery touch. Vegelight 1214 LC is a mixture of coconut alkanes with coco caprylate/caprate that has a very similar feel to D5, and is a good pigment wetting and dispersing agent, particularly suitable for preparing BB creams. Vegelight WSI is a w/o emulsifier also designed especially for BB creams [INCI: Coconut alkanes, polyglyceryl-3 polyricinoleate, disteardimonium hectorite].

Daikon Seed Extract from Natural Plant Products Inc is a natural emollient derived from the seeds of Raphanus sativus. Comprising a mixture of C18, C20, and C22 fatty acids, it is extremely light coloured and odourless. It offers a delicate slip with good absorption and presents a sensory profile more closely associated with esters and silicone emollients. Tests show that Daikon Seed Extract improves dry comb, reduces hair breakage on repeat combing and boosts hair shine, outperforming phenyl trimethicone.

While the majority of silicone alternatives are aimed at replacing volatile and low viscosity silicones, Soft Butters from Greentech are a range of plant derived products specifically developed to replace silicone gums and elastomers. Soft Butters deliver a superior emulsion structure and enhanced viscosity. They are available in apricot, argan, avocado, baobab, camellia, cotton, evening primrose, inca inchi, olive, peach kernel and sweet almond, which comprise the named oil with its hydrogenated counterpart. Dermofeel Viscolid [INCI: Hydrogenated vegetable oil] from Dr. Straetmans is a natural oil thickener supplied in a powder format with a melting point of approximately 60°C. It is used to convert liquid oils into soft, creamy textures. The thickening effect is based on a delicate network of fine lipid crystals that, upon contact with the skin, melt and form a liquid phase with the sensorial profile of the oil mixture used.

Global 4075 from Global Seven is offered as a naturally derived ingredient to thicken vegetable and other oils in anhydrous systems. It is a mixture of glyceryl isostearate and caprylic/capric glycerides that is mixed with sodium stearate before being combined with the other anhydrous components, and it is possible to create products ranging from flowable gels to hard sticks. Alban Muller presents Ecogel as a patented optimised combination of ingredients of natural origin derived from a green process. It is a mixture of lysophospholipids, xanthan gum, sclerotium gum and pullulan, and is claimed to be the first natural phospholipid-based gelling/emulsifying agent available to create natural gels and creams with an ultra-soft and light skin feel.

Soft Butters from Greentech are intended to replace silicone gums, and include avocado and apricot kernel variants

References
1. O’Lenick A., (2009) The quest for D5 replacements; Household and Personal Care Today, 3, 40-43.

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