Modern cleansing products and the surfactants used in them
This feature focuses on personal care in the bathroom, which primarily involves cleansing products and the surfactants that are used in them.
At SCS Formulate 2015 SPC heard that micellar waters were the latest thing in facial cleansing. This was puzzling, as a characteristic of surfactants is that they form micelles when introduced into water. So what is micellar water? One website describes them as “quick, easy and chemical-free”, adding: “What’s not to love about the latest beauty innovation, the micellar water cleanser?” Further investigation found that “micelles are tiny balls of cleansing molecules that float in water and trap impurities”.
Turning to science instead of marketing hype, we find that micellar waters are low concentrations of surfactants in water. But for micelles to form the surfactant must be present above its critical micelle concentration (CMC). This is defined as the concentration above which micelles are spontaneously formed. The next step in understanding the product chemistry is to look at the principal ingredients in some retail brands.
Looking at the formulation of micellar waters, it appears they simply need a low level of a mild surfactant in water with the addition of one or more glycols and/or a poloxamer to help with the solubilising of facial impurities. Besides the disodium cocoyl glutamate, polysorbate 20 and disodium cocoamphodiacetate shown in the INCI lists above, various glucosides, betaine and PEG-40 hydrogenated castor oil are very effective.
Seppic gives the CMC of the surfactants that it recommends for micellar waters; thus the CMC for Sepiclear G7 [INCI: Heptyl glucoside] is given as 8.2g/L; that of Oramix CG 110 [INCI: Caprylyl/capryl glucoside] is 1.7g/L; and Oranal LCG/E OD [INCI: PEG-40 glyceryl cocoate, sodium coceth sulphate] is 2.1g/L. Although the CMC is affected by temperature and other constituents, including glycols, which raise the CMC of surfactants, it is unusual for the surfactant concentration to exceed 1%w/v.
In addition to the surfactant system and glycols, most products also contain additional beneficial ingredients and natural extracts. As micellar waters are considered leave-on products, it is important that additives are not sticky but impart a silky skin after feel. Seppic suggests the addition of Aquaxyl [INCI: Xylitylglucoside, anhydroxylitol, xylitol] to moisturise the skin, improve water circulation and reduce water loss.
Hydrovance from AkzoNobel is hydroxyethyl urea, said to provide synergistic moisturising when used with glycerin and other humectants. Protameen Chemicals supplies Proaqua ISP [INCI: Isosteareth-200 palmitate], which has good solubilising and moisturising properties. It also imparts a soft after feel without oiliness. Brasca supplies a number of fruit waters under its CytoFruit trade name, which are extracted from the fruit using physical processing and are certified organic. They retain all the natural benefits of the original fruit and could make a good basis for micellar waters.
Micellar water may be on-trend, but face and body washes are still the norm in personal cleansing. For decades these have been based on sodium laureth sulphate (SLES) with cocamidopropyl betaine, and this combination still dominates the mass market shelves. However, other surfactants are making an impact. Innospec offers Iselux [INCI: Sodium lauroyl methyl isethionate] as a primary surfactant that provides a dense creamy foam, is mild on the skin, suitable for clear formulations and readily thickens with salt, betaine and other amphoterics.
Crodasinics from Croda have been available for many years but are certainly worth consideration if formulating mild body washes and shower gels with good lathering properties. They are based on sodium lauroyl sarcosinate and are known to adsorb onto human skin, exhibiting optimum substantivity at slightly acidic pH5. The adsorbed layer of sarcosinate may be responsible for the perceptible skin conditioning effect imparted when included in rinse-off formulations.
Sarcosinates and amphoacetates both appear in many of the more prestigious body washes. Specifeel EM from Brasca is a specially formulated base that can be used immediately by a simple dilution with water to formulate instant toiletries. Comprising sodium lauroyl sarcosinate, sodium cocoamphoacetate, lauryl glucoside, sodium methyl cocoyl taurate and C12-C13 alkyl lactate, it is recommended for formulating very mild toiletry products that are transparent with a pleasant creamy foam and good viscosity.
Using blends reduces material inventories and simplifies manufacture. Huntsman provides blends of primary and secondary surfactants as Empicol XCT 14 and Empicol XCT 15 that are suitable for manufacturing body washes. XCT 14 is a mixture of sodium C14-16 olefin sulphonate with sodium cocoamphoacetate and cocamide MEA that is exceptionally mild but has good foaming properties, while XCT 15 is sodium lauryl sulphate with cocamide MIPA. Huntsman also produces Empicol C carboxylates as co-surfactants suitable for body wash and other surfactant-based applications. Alkyl ether carboxylates are extremely mild to the skin, colourless, highly biodegradable and have excellent foam boosting and stabilising properties.
Suggested as a secondary surfactant by Lonza, Amaranth S [INCI: Sodium cocoyl hydrolyzed amaranth protein] is a natural foaming peptide based on an organic source of amaranth from Peru. It is a mild foam booster and is compatible with sebum without losing its foaming properties. The presence of the protein base enhances substantivity to skin and hair, leaving behind an elegant, conditioned feel after rinsing. Another protein-based material is Proteol APL from Seppic [INCI: Sodium cocoyl apple amino acids], which is said to develop a dense foam of fine, compact bubbles. It is a non-irritant for eyes and vaginal mucosa, and is ideal for sensitive rinse-off applications.
Olive oil is a popular starting material for many cosmetic ingredients including surfactants. Kalichem Italia produces Olivoil Surfactant [INCI: Potassium olivoyl hydrolyzed wheat protein] as a non-ethoxylated, sulphate-free, vegetal-derived surfactant. It is obtained through condensation between the carboxyl group of fatty acids derived from olive oil and the amino group of hydrolysed wheat proteins. The result is an amphiphilic structure with a fatty amide bond, having the lipophilic side represented by olive oil fatty chains and the hydrophilic side by wheat polypeptides.
The foaming properties of Olivoil Surfactant are comparable to those of SLES but because of the long chain fatty acids it is exceptionally mild and leaves the skin feeling soft, moisturised and smooth. Kalichem suggests using it in combination with Olivoil Glutamate to optimise the detergency and skin benefit properties of the two materials. If added at 2-5% to traditional surfactant systems both materials are claimed to reduce the irritancy and harshness of SLES. Higher percentages are suggested where an immediate feel of hydration, smoothness and softness is required. Also from Kalichem is Olivoil Fruttoside [INCI: sodium olivoyl/cocoyl aminoacids fructoside], which combines high foaming power with exceptional mildness. It also reduces transepidermal water loss, even when applied via a shower gel.
BC Cosmetic and Food also markets ingredients based on olive oil: Beautyolea S3 is olive oil PEG-7 glycerides with emollient and lubricant properties when used as a secondary surfactant. Beautyolea S4 is sodium PEG-7 olive oil carboxylate that may be used as a primary surfactant to provide a creamy, shining and small-bubble foam. Also available from BC are a number of amphoacetates including sodium arganamphoacetate, sodium babassuamphoacetate, sodium mangoamphoacetate and many others based on natural oils and butters.
Continuing the natural theme, Soapnut Extract Powder [INCI: Sapindus trifoliatus fruit extract] from Ichimaru Pharcos is obtained from the fruit of the soapnut tree from the Indian subcontinent. It is supplied as a powder and it is suggested that 1% be added to traditional surfactant systems to reduce irritation and to improve foam density. It also has antioxidant and deodorant properties.
Taking the opposite approach to the minimalistic micellar waters are high oil content body washes. According to Barbara Brockway of IMCD, in-shower moisturisers are to personal care in the bathroom what BB creams are to skin care. Conditioning bodies after showering is the next step for innovation in the bathroom.
Empicol PES 101 from Huntsman may be used for preparing high-oil-content body cleansing products. With the INCI name sodium PPG-16/PEG-2 laureth sulphate, it is described as an extended chain surfactant that exhibits ultra-low interfacial tension between oil and water. It is said to provide emollient properties with a light non-greasy skin feel and it may be used to formulate micro-emulsions with polar and non-polar oils, and with silicones.
Miracare SLB from Solvay is described as an innovative blend of surfactants [INCI: Sodium trideceth sulphate, sodium lauroamphoacetate, cocamide MEA] that forms a close packed network of spherulites, which are concentric surfactant shells of lamellar surfactant bilayers. When Miracare SLB is used at 30% or above it is capable of absorbing as much as 40% sunflower oil or 30% soybean oil; the oils leave the skin feeling silky, soft and moisturised for up to 24 hours after application. Despite the high oil content, body washes based on Miracare SLB deliver a rich, dense foam and, because of their structure, they can suspend insoluble particulates.
Suggested as an additive to moisturising shower gels, DuraQuench IQ SA from Croda forms a structural bilayer on the skin, visibly increasing skin moisturisation by regulating water loss. It interacts with the lipid bilayers of the stratum corneum to reinforce the skin’s natural barrier. It is a mixture of cetyl alcohol, isostearyl isostearate, potassium cetyl phosphate, cetyl stearate and stearic acid, and it is recommended to be added at 1% to rinse-off applications.
To test the efficacy of DuraQuench IQ SA as a moisturising additive for wash-off applications, the physical condition of the skin was measured by examining barrier integrity, skin hydration and dry skin flaking. DuraQuench IQ SA was added at 1% to a body wash and skin condition was monitored after use. The DuraQuench IQ SA formulation displayed a consistently higher level of hydration when compared with the control sample. At the same time a sensory study showed a significant increase in perceived skin softness and moisturisation.
Amisol Trio from Lucas Meyer is an eco-friendly active biolipid complex extracted from soybean and suitable for formulating in-shower moisturisers. It is composed of phospholipids, glycolipids, phytosterols and linoleic acid. It provides super-fatting properties and improved moisture balance in the skin. Greentech has mixed natural oils with lysine to create its Aquasiloils range of water-soluble oils for adding to personal cleansing systems including face and body washes. Currently three are available: Aquasiloil Sweet Almond, which foams strongly and has good cleansing properties; Aquasiloil Inca Inchi, which has low foaming properties but has skin improvement properties; and Aquasiloil Argan, which is better suited to emulsions for regenerating the skin’s barrier properties.
Providing additional skin care benefits from body washes often requires solubilising the additive. NatraGem S150 NP [INCI: Polyglyceryl-4 laurate/sebacate, polyglyceryl-4 caprylate/caprate, aqua] from Croda has been specifically developed to be a highly efficient solubiliser for lipophilic cosmetic actives and their carrier oils. NatraGem S140 NP is a similar composition for solubilising fragrances and essential oils.
Adding texture to sulphate-free surfactant systems is the function claimed for Balance RCFg from AkzoNobel. It is an acrylates copolymer, described as a versatile, efficient, multifunctional ingredient that provides thickening and rheology modification in a wide range of surfactant systems. It may be used in clear compositions and is suitable for cold-processing. It is also recommended for shaving and for hair products.
Rheoluxe 811 [INCI: Steareth-100/PEG-136/HDI copolymer] from Elementis imparts rheological control to sulphate-free surfactant systems and shows a synergy with salt. It also helps build a rich and voluminous foam with a creamy feel. Glucamate CCO thickener [INCI: Methyl glucose caprate/caprylate/oleate, propanediol] from Lubrizol is recommended for thickening ethoxylate-free and sulphate-free surfactant systems. It is supplied in liquid form and can be used for cold processing. Recommended use levels range from 0.5-3%, depending on application and amount of thickening required.
For a fun product, Aston Chemicals entered Silly Stringy Springy Bath Jelly Putty for the Laura Marshall Memorial Award at SCS Formulate 2015. Its primary ingredients were 50% Romol MAP30K and 5.5% Dermothix 75L with fragrance, preservative and colouring, with the balance being water. Romol MAP30K from Eleco Chemical is a 30% active solution of potassium laureth sulphate offered as a mild surfactant with good foaming properties. Dermothix 75L with fragrance, preservative and colouring, with the balance being water. Romol MAP30K from Eleco Chemical is a 30% active solution of potassium laureth sulphate offered as a mild surfactant with good foaming properties. Dermothix 75L from Alzo is a mixture of disteareth-75 IPDI with glycereth-7 caprylate/caprate. The combination of these two ingredients provides the unique jelly-putty texture.