Even if the Free From trend has subsided a little in the cosmetic industry, consumers buying online still love using this shortcut to do their search. One of these popular shortcuts or searches is sulfate free, as Google Trends shows UK, UAE, Australia and USA are among the top 11 countries where this search term is trending globally. Natural shampoo is also another trending search even if not as popular as the sulfate free term.
This means that formulating today for tomorrow’s shampoos needs to move towards natural and sulfate free and when I say natural, I mean a natural with green chemistry design. In this article I will go through the key challenges to formulate a performing, natural derived, 1,4 Dioxane and sulfate free shampoo.
Sulfated surfactants alternatives
Sulfates surfactants such as SLS and SLES have been really popular in the cosmetic industry with their convenient performance and their replacement is not as straight forward as one might like. The low cost, flash foaming and the salt thickening properties make them really easy to formulate with. Despite this, their bad reputation with consumers combined with the trend towards a circular economy with green chemistry materials and the issues around the presence of 1,4 dioxane in ethoxylated sulfated surfactants, are making them obsolete for the cosmetic industry. On top of this the Cosmos natural and organic beauty standard has also announced the ban of sulfated surfactants by 2029.
The first alternative to consider is Alkyl polyglycosides (APGs), a family of non-ionic biodegradable surfactants made from plant derived sugars and fatty alcohols. As they have been around for a while they are relatively low cost, however, they need extra support for hair conditioning and foam boosting.
A second green alternative is amino acid based anionic surfactants, like Glutamates made from coconut oil and sugars. Their biomimetic structure come with great mildness for skin and eyes and hair substantivity, however, depending on the pH, they may need support to boost the foam.
A third green alternative is Glucamides a relatively new group of non-ionic surfactants made from glucose and natural oils like sunflower and palm oil. They come with great foaming, cleaning ability and mildness, with a low Carbon footprint. They are also readily biodegradable and have no aquatic toxicity. Some of them also come with hair colour protection data making them really attractive for haircare applications.
There is also a fourth green alternative, non-ionic bio-surfactants with INCI name Glycolipids coming from bio fermentation of glucose and non tropical oils, called Sophorolipids. Given their manufacturing method they require no solvent and low energy processes. They come with good cleaning performance, full biodegradability, low aquatic toxicity and mildness. At present they are mainly used as co-surfactants and co-emulsifiers, however their use has great potential to increase.
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Thickening
Thickening is another challenge formulators face when it comes to formulate without sulfated surfactants. There are currently two approaches to increase the viscosity of these systems: one is based on introducing a gelling agent increasing the viscosity of the water phase, and one based on altering the surfactants micellar structure.
The first approach involves the use of natural polymeric thickeners such as Xanthan gum. This is frequently used in natural shampoos however it is limited in the quantity and quality of viscosity it can deliver. Luckily, there is constant innovation in our industry and a great example of this is the recent launch at In-Cosmetics Global of the Carbopol® Fusion S-20 (INCI Starch acetate/adipate), a natural derived polymer, ultimately biodegradable with similar performance to carbopols and even great clarity.
The second option is using surfactants concentrates acting on the micellar structure such as Glyceryl caprylate and Sorbitan oleate or Lauryl Glucoside and Disodium Cocoyl Glutamate. These blends can give nice rheology but the increase in viscosity is dependent on the formulation and other surfactants present.
Preservatives
This is also a challenge for sulfate free shampoos following green chemistry principles. Organic acids, a cost-effective choice now available also from plant sources, require a pH below 5.5 which may cause eye irritation when used in shampoos. Phenoxyethanol and Benzyl alcohol may reduce the viscosity, therefore careful consideration needs to be taken to select a preservative system that is compatible with the application and the formulation. To help formulators find the best preservation candidates for their formulations I wrote a compendium of green chemistry ingredients that can be used in cosmetic preservation, “The Green Chemist’s Handbook for Cosmetic Preservation“ (1). In this book formulators can select ingredients according to pH range, natural content, solubility and regulatory status. Once the potential candidates are identified more information can be obtained from the UL Prospector premium platform (2).
Conclusions
Consumers desire for sulfate free is growing along with the economic shift towards a circular economy supporting green chemistry materials. The transition towards sulfate free is not going to be easy and it will take time, however there are performing and mild alternatives worth exploring at this moment in time to prepare for this long term shift and there is more innovation coming to support the industry in this transition. It will be interesting to see the new launches at the next In-Cosmetics Global Sustainability Zone and how regulations, especially the ones pushing for a circular economy, may impact this transition long term.
1 The Green Chemist https://thegreenchemist.com/
2 UL Prospector premium platform https://www.ulprospector.com/pcc-basic
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