It is known that, among their many characteristics, surfactants result in the formation of foam. Surfactants are intentionally used in excess in shampoos and soap systems to create foam, and the higher the concentration, the stronger the foam effect of the product.
This sounds perfect when we are talking about hair care products; however, this represents a problem when we are dealing with skin care emulsions. An excessive amount of emulsifier, in combination with alcohols or long-chain esters, also results in the formation of micro-foam.
In some formulations, using more than 8% of alcohols and long-chain esters in association with self-emulsifying waxes is enough to provide what we call a "foaming effect.” Formulators may face this problem while developing a product that contains a high amount of oils, as they will certainly need enough emulsifier to prevent creaming.
Another common situation is when we want to formulate a creamier emulsion with high viscosity. The excess of emulsifier leads to consumer rejection of the product. Consumers will see a white trace (micro-foam) while spreading the product on the skin, and scrubbing more will only increase the formation of foam.
The solution is, in part, simple: we should decrease the concentration of emulsifiers and waxes. But the result will obviously be a reduced viscosity. We should use polymers to compensate for the loss of viscosity, since, unlike surfactants and waxes, polymers do not cause a foaming effect.
There are 2 classes of polymers: synthetic and natural. Both contribute to the viscosity of the system. The most indicated for emulsions with high concentration of oil are Acrylates/C10-30 Alkyl Acrylate Crosspolymer (Pemulen TR-2). They not only provide viscosity, but also stabilize oil droplets, adding to the stability of the system.
This emulsifying power is not seen in vegetal polymers. Therefore, in emulsions with high oil content, we can indeed use vegetal polymers, but always associated with synthetic polymers. An excellent option is the association of Acrylates/C10-30 Alkyl Acrylate Crosspolymer and xanthan gum. The combination of these polymers with waxes and emulsifiers ensure a formulation with no foaming effect.
In emulsions that do not have high oil content, it is possible to use other synthetic polymers such as carbomers (Carbopol® series) or Sodium Polyacrylate Starch (Makimouse). To guarantee an even more pleasant final sensorial, we can add low viscosity dimethicone to improve spreadability. Beyond sensorial benefits, dimethicones also form a synergetic system that will further reduce the foaming effect.
|Desenvolvimento de Emulsões e Géis Cosméticos by IPUPO – Educational
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Lucas Portilho is a cosmetology expert with IPUPO, the union of high-level professionals who currently work in the cosmetic markets throughout Brazil. Their main objective to bring and share knowledge to enable health professionals through updated teaching methods at the highest level. Postgraduate professionals from recognized institutions have higher wages and occupy ever more important positions within companies.
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