The right oils & waxes for the job

Published: 9-Jun-2009

The oil phase of a cosmetic emulsion may include natural and synthetic oils, vegetable and animal fats and waxes and also encompass butters, silicones and esters; a suitable title for this group of materials might be hydrophobic ingredients, or maybe lipophilic constituents. John Woodruff takes a look at what is available

The oil phase of a cosmetic emulsion may include natural and synthetic oils, vegetable and animal fats and waxes and also encompass butters, silicones and esters; a suitable title for this group of materials might be hydrophobic ingredients, or maybe lipophilic constituents. John Woodruff takes a look at what is available

In addition to the elements mentioned in the introduction the oil phase also includes the majority of emulsifiers, but these were described in SPC September 2008 (p43-48, Green & clean) so with a few exceptions they will not be included in this feature.

What is a wax? By definition they are esters of long-chain fatty acids reacted with higher alcohols. Non-pedantically, materials that are similar in properties to true waxes are also regarded as waxes. They may be natural secretions of plants or animals or artificially produced by purification from petroleum or be completely synthetic.

Examples of different types of cosmetic waxes are beeswax, jojoba oil, paraffin wax and silicone wax. Beeswax is credited with being the principal component in Galen’s Cold Cream, formulated in Roman times and it is still much used in cosmetics today. It is a complex mixture of free fatty acids, hydrocarbon resins and esters of C16-C30 fatty acids reacted with C26-C30 fatty alcohols. Jojoba oil is a wax that it is liquid at ambient temperatures. It is expressed from the seed of Simmondsia chinensis and is composed mainly of C18-C24 esters.

Paraffin wax is an alkane hydrocarbon with the general formula CnH2n+2 where n is 20-30. Differing carbon chain lengths give different melting points. Microcrystalline wax is similar but composed mainly of branch-chained hydrocarbons and ozokerite is a naturally occurring variety. The three hydrocarbon waxes have similar properties but their crystal structure and melting points differ so careful selection is necessary to obtain the best results for various applications.

Silicones are generally thought of as oil-like liquids or they may even be volatile substitutes for ethanol. However, the alkyl silicones are waxy solids and Siltech has launched four silicone polymers with wax-like properties under its Silwax trade name. They have both solid and liquid alkyl groups on the same silicone backbone and the resultant waxes are thixotropic and liquefy under pressure. They feel like petrolatum on the skin; they spread rapidly, have good gloss but are non-greasy. They are of particular interest in hair products because of their glossing properties and in pigmented cosmetics because they inhibit syneresis and improve glide.

Another wax much used in cosmetics is lanolin wax, which is produced by the multi-stage refining of wool grease, followed by low temperature fractional crystallisation. The fractional crystallisation separates the liquid esters, known as lanolin oil, from the solid wax esters, which make up anhydrous lanolin. It has similar chemical characteristics to anhydrous lanolin but with a higher melting point that can convey extra stability to formulations, particularly at higher temperatures.

BEYOND THE COMMODITY

A problem with materials like oils and waxes is that they are regarded as commodity items so individual companies are reluctant to invest time and money into promoting their properties. Exceptions do exist and Northstar Lipids has been investigating the effect of certain vegetable oils on the skin. It has looked at emolliency, transepidermal water loss (TEWL), skin firmness and skin elasticity and attempted to relate results to their fatty acid profile and content of longer chain polyunsaturated fatty acids (PUFAs) and micronutrients.

Studies were made over the last 18 months to determine the relative efficacy of a number of new and not so new natural oils to determine whether or not the ratio and content of the fatty acids made a significant difference to oil functionality. It was found that oils rich in oleic acid like almond and olive tended to have a more immediate impact and oils richer in longer chain unsaturated fatty acids like hemp, blackcurrant and kiwi appeared to have longer term benefits, but the differences in performance were, statistically, only small.

According to Northstar this is not necessarily a negative point since the findings demonstrate that most if not all oils have good natural emolliency but it does lend some clinical support to the view that this group of ingredients can be interchanged without significant adverse effect on the end product. Northstar found that strawberry, raspberry, elderberry and oat oils have good emolliency with the oat and elderberry as top performers, possibly due in part to co-factors in the oil such as elevated levels of natural antioxidants and micronutrients.

In conclusion the results from these studies suggest that the ratio and content of individual fatty acids, omega 3:6:9, has only a marginal impact on product efficacy but that other factors such as micronutrients and the content of longer chain PUFAs like gamma-linolenic acid and stearidonic acid may be more significant in improving skin condition over long-term application. Furthermore, balanced formulations appear to support the best all round improvement in emolliency, TEWL, firmness and elasticity. Building on this research Northstar has formulated NorOmega PC 369 using lipids from naturally grown, non-genetically modified Helianthus annus (sunflower) seed oil; Camelina sativa (camelina) seed oil; Echium plantagineum seed oil and Ribes nigrum (blackcurrant) seed oil with a ratio of omega 3:6:9 of 1:1:1.5 respectively. Other blends are available and a wealth of technical data is available on the Northstar website.1

The Cornelius Technical Centre undertook studies of natural waxes. In this case the aim was to assess the effect of several wax types on oils of different polarity, thus providing results to aid a formulator in selecting a wax for the attributes it can bring to a formulation. Four basic oil types were used: esters, mineral oil, vegetable oil and a silicone cross-polymer. These were used in conjunction with a range of polyethylene waxes, plant waxes, petrochemical waxes and solid esters with each wax added at 30% into the oils.

The wax and oil were heated, mixed and poured into a lipstick mould to form sticks. Where the resulting mixture was too soft to form a stick no further assessment was carried out. The ones that formed a stick were then assessed for tactile properties, in particular for pay-off and cushion and also for stick strength. It is realised that ratios of wax to oil would be optimised in final formulations but initial results point to the best combinations.

Pelemol GMB from Phoenix Chemical [INCI: Glyceryl behenate] is a large molecular weight ester that was found to give ethylhexyl palmitate and light liquid paraffin sticks a cushioned feel to the skin. Polyethylene combined with castor oil gave lots of cushion making it a good choice for lipstick formulations along with white and synthetic beeswax, carnauba and candelilla, which gave exceptionally strong sticks. Candelilla and ozokerite produced very strong sticks with polyisobutene and ozokerite would be the best choice for polyisobutene-based stick lip glosses.

It was found that behenyl behenate gave the strongest stick with ethylhexyl palmitate with good pay-off and some cushion and would possibly be more suited for use in applications where a drier, less greasy feeling stick is desired. Ceresin and ozokerite performed best at strengthening the stick based on Jeesilc O, a silicone cross-polymer material, and is suggested for formulations where high levels of silicones are used.

Croda Europe has produced a very informative brochure about the formulation of lipsticks available with the title Kiss Technology. It describes the various oils and waxes to be found in lipsticks and the properties that they impart to the finished product. Of particular interest is the section on oil-wax interactions and another on overcoming syneresis. There are also details on improving gloss, pay-off and durability and on pigment wetting to aid manufacture.

There are few mainstream cosmetic products that do not incorporate a silicone derivative and cyclomethicones are much used for their transient cooling effect and the satiny skin feel they impart to emulsions. However there are concerns about their use and various alternatives are suggested. The Cornelius Technical Centre tried diverse blends of esters with Jeesilc PS-PTLV [INCI: Phenyl trimethicone, bis-vinyl dimethicone/dimethicone copolymer] and determined their spreadability coefficients. Those within the right range were then examined by a sensorial panel that compared slip, skin penetration and dry feel and after feel. It was found that 5% Jeesilc PS-PTLV with 95% ethylhexyl isononanoate compared very favourably with cyclopentasiloxane.

THE NEW ALTERNATIVES

Alternatively Phoenix offers Pelemol D5R; a mixture of isononyl isononanoate, ethylhexyl isononanoate and cetyl/behenyl dimethicone, said to be specifically formulated to mimic the sensory properties of cyclopentasiloxane.

Offering alternatives to existing materials that have fallen out of favour is not uncommon. Petrolatum is a basic constituent of many cosmetic products but some consumers prefer to avoid materials originating from the petroleum industry. An alternative with Ecocert approval is a blend of Ricinus communis (castor) seed oil with hydrogenated castor oil and Copernicia cerifera (carnauba) wax sold under the trade name Vegetable Petrolatum R15 by CRM International.

Lanolin was long the favourite ingredient of the oil phase but fell out of favour for a variety of reasons, many of them spurious. Covasterol from LCW is offered as an Ecocertified alternative. It is a mix of glyceryl isostearate, isostearyl alcohol, Brassica campestris (rapeseed) sterols, Butyrospermum parkii (shea butter) and Euphorbia cerifera (candelilla) wax. Literature from LCW shows it to hold ten times more water than lanolin, to confer similar gloss and to have a similar effect on skin suffering from scaling, roughness and dryness. Another alternative to lanolin is Hydracire from Gattefossé. Launched at in-cosmetics 2009 its INCI name is Jojoba/mimosa/sunflower seed wax polyglyceryl-3 esters and details from the supplier show it be an effective substitute.

In order to add value to natural oils many companies produce blends to combine properties and to produce unique effects. For example, the Bio-Inov range of butters from CRM International is designed to give products with a unique texture that show easy skin penetration and have excellent skin tolerance. Each product has a butter-like, highly stable texture and included in the range are mixtures of Butyrospermum parkii (shea butter) with either olive oil, Camelina sativa (camelina) seed oil, Olea europaea (olive) fruit oil or Argania spinosa kernel oil. The butters have enhanced softness and creaminess compared to standard butters, says the supplier.

Also from CRM, The Phytomoisturisers range is a group of products combining phytosterols and olive unsaponifiables with specific oils in a stable base. One example is Crambe abyssinica seed oil with Olea europaea (olive) oil unsaponifiables, hydrogenated vegetable oil, glyceryl stearate, phytosterols and tocopherol. The materials all have very high water absorption capacity and give 24 hour hydration. The same company markets many other combinations, each reputed to have cosmetic benefits.

The Fanning Corporation is probably best known for its products based on meadowfoam oil. Anti-Aging Skin Complex is a blend of ingredients, which moisturise the skin at different levels. Meadowfoam Estolide helps adjust the hydration levels of interstitial spaces and provides significant moisturising benefits perceived as softer, more pliant tissue. Its structure is ceramide-like and it is offered as a cost effective alternative. Meadowfoam Delta-Lactone is a skin moisturiser to help reduce irregularities and improve the appearance of skin. The Fancor Abyssinian Oil, Crambe abyssinica seed oil, moisturises and protects the epidermal layers and the beta-sitosterol content maintains the integrity of cellular and tissue structure thereby keeping skin feeling and looking youthful. Olive oil unsaponifiables provide emolliency and Fanoliv ActivE contains vitamin E as a natural antioxidant while the safflower oil is a rich source of linoleic acid, an essential omega-6 fatty acid.

Modifying the rheological properties of oils and waxes or thickening water-in-oil emulsions can present problems to the formulator. Rheopearl, a dextrin ester from Chiba Flour Milling Co is compatible with esters, higher alcohols, tri-glycerides and hydrocarbons. It may be used at 2% - 5% to improve emulsion stability and at higher levels to completely gel the oil phase. It is also useful when anhydrous products like salt scrubs need to be thickened and can be used to improve the structure of stick products such as lipsticks and anhydrous antiperspirants. Sisterna offers Sisterna A10-EC [INCI: Sucrose tetrastearate triacetate] as an alternative to beeswax and lanolin in lipsticks and balms and for thickening oils. It is claimed to reduce the greasy and sticky sensation of oils and to improve their spreadability.

A novel alternative to the usual scrub agents are a number of materials from H Foster & Co. The sugar scrubs are granules of sugar coated with a wax shell for use in exfoliating products. The base should be non-aqueous to a maximum of 5% water. On application the exfoliating action cracks the wax shell revealing the sugar crystal which performs the exfoliating action and at the same time the wax shell part is finely smeared onto the exfoliated skin leaving a protective moisturising layer. H Foster also supplies peeling waxes, which are tiny beads of wax suitable for use in aqueous systems as well as oil-based ones. They work by pressure during application giving the exfoliating action and smearing the wax over the skin to give a smooth moisturising effect afterwards.

EXOTIC ADDITIONS

No article on oils would be complete without a round-up of the latest exotic oils from around the world. Beraca supplies ingredients from the Amazon rainforest. It has just added Pentaclethra macroloba seed oil to its extensive collection of oils and scrub agents. Biochemica International specialises in butters based not only on the usual ingredients but also on some more exotic ones such as Lemon Grass Butter; Lime Butter, Matcha Green Tea Butter and Mowrah Butter. It also publishes an extremely useful guide to the formulation of butters.2

Butters are also available from Zenitech and IMCD. Zenitech provides various fruit butters such as lemon, lime, raspberry and orange and has recently launched Meadowfoam Butter comprising Limnanthes alba (meadowfoam) oil, octyl dodecanol and beeswax. IMCD markets Grape Seed Butter RES-N [INCI: Vitis vinifera (grape) seed oil, butyrospermum parkii (shea butter), rice bran wax & resveratrol]. This is a blend of 100% natural vegetable oils and waxes with no hydrogenated fats or preservatives. Besides the usual natural oils and waxes IMCD also supplies Kendi Oil [INCI: Aleurites moluccana seed oil] and Nyamplung Oil [INCI: Calophyllum inophyllum seed oil] from Indonesia.

Finally, from IMCD comes this novel product: Phytomoisturizer Olive Effervescent [INCI: Olea europaea (olive) fruit oil, Olea europaea (olive) oil unsaponifiables, hydrogenated vegetable oil, phytosterol, sodium bicarbonate & citric acid]. This white buttery paste is a combination of the skin softening, buttery fractions of olive oil and hydrogenated vegetable oil with olive phytosterols and fine water soluble crystals that fizz as soon as they are moistened. It is suitable for all anhydrous products designed for use on the face, hands, body and feet and adds naturally derived lipids to skin giving protection and moisturisation needed before using a depilatory cream or shaving.

1. www.northstarlipids.co.uk

2. www.biochemica.com

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