Sustainable Cellulose-derived Rheology Modifiers for Personal Care Applications
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Presented by: Cindy Delvalle
Introduction: Rheology modifiers (RMs) play a key role in Personal Care products as they affect formulation stability, product performance and customer perception. Acrylic-based RMs with INCI names like Carbomer and Acrylates Copolymer are currently the most common class of RMs in the market, but they are facing pressure given their petrochemical origin and lack of biodegradability. The market is looking for versatile, efficient and cost-effective innovations with improved sustainability profiles to substitute acrylic-based RMs. In this paper we introduce a new cellulose-derived RM product (INCI: hydroxyethyl methylcellulose, HEMC) and characterize its performance in a wide variety of personal care formats including shampoos, conditioners, styling gels, skin lotions and creams. Further studies were conducted in a shampoo format to optimize suspension benefits, and here we present results obtained using blends of the HEMC product with commercial xanthan gums.
Methods: The formulations were made by first adding the HEMC to the water phase under vigorous mixing. Subsequently, surfactants, emulsifiers, oils, and other ingredients were added as required by the specific formulation. Relevant benchmark RMs (INCI: hydroxyethyl cellulose, xanthan gum, carbomer, acrylates copolymer) were also included in the study for comparison. The performance of the RM was assessed by visual and tactile observations paired with rheology (amplitude sweeps, frequency sweeps and shear rate sweeps) and texture analyzer tests.
Results/Discussion: The new HEMC product is a nonionic cellulose ether supplied as a glyoxal-free powder that is readily soluble in cold or warm water, and stable at pH values in the 3-10 range. It contains 80 wt.% cellulose and achieved inherent ultimate biodegradation under OECD 302 testing. This HEMC product was found to be a suitable RM for hair care formulations. Shampoo and conditioner formulations were stable and showed optimum viscosity and shear thinning profiles with use levels in the 0.7-1.2 wt. % range. As compared to a commercial high molecular weight Hydroxyethyl Cellulose RM, the new HEMC product showed higher efficiency and reduced stringiness.
In addition, the slightly hydrophobic nature of the polymer backbone enabled this HEMC product to work as polymeric emulsifier and stabilizer in skin formulations and O/W emulsions (as primary or secondary emulsifier depending on use level). Formulations made with 0.4-1% HEMC were stable and had optimum viscosity, yield points and shear thinning behavior. And while the performance was not identical to that of carbomer (at the same use level), the HEMC outperformed commercial high molecular weight Hydroxyethyl Cellulose and provided rich, non-sticky, and non-stringy lotions and creams.
In specific applications, the suspension benefits provided by using HEMC are not sufficient. Blends with natural gums were explored as these materials can form networks that often provide suspension. The RM combination (HEMC and Xanthan Gum) enabled the formulation of clear and stable shampoos with a rich, smooth, and uniform texture that showed enhanced suspension properties compared to shampoos containing either RM on its own, or those thickened with salt. Such combinations are biodegradable alternatives to acrylic-based RMs and can deliver similar sensory and performance attributes.
Conclusion: The new cellulose-based HEMC product is a suitable RM for a wide range of hair and skin care formats. It provides optimum stability, viscosity, and sensory properties with a more sustainable profile than the current synthetic RMs. In addition, blends of the HEMC with natural gums were found to further enhance suspension properties.
Methods: The formulations were made by first adding the HEMC to the water phase under vigorous mixing. Subsequently, surfactants, emulsifiers, oils, and other ingredients were added as required by the specific formulation. Relevant benchmark RMs (INCI: hydroxyethyl cellulose, xanthan gum, carbomer, acrylates copolymer) were also included in the study for comparison. The performance of the RM was assessed by visual and tactile observations paired with rheology (amplitude sweeps, frequency sweeps and shear rate sweeps) and texture analyzer tests.
Results/Discussion: The new HEMC product is a nonionic cellulose ether supplied as a glyoxal-free powder that is readily soluble in cold or warm water, and stable at pH values in the 3-10 range. It contains 80 wt.% cellulose and achieved inherent ultimate biodegradation under OECD 302 testing. This HEMC product was found to be a suitable RM for hair care formulations. Shampoo and conditioner formulations were stable and showed optimum viscosity and shear thinning profiles with use levels in the 0.7-1.2 wt. % range. As compared to a commercial high molecular weight Hydroxyethyl Cellulose RM, the new HEMC product showed higher efficiency and reduced stringiness.
In addition, the slightly hydrophobic nature of the polymer backbone enabled this HEMC product to work as polymeric emulsifier and stabilizer in skin formulations and O/W emulsions (as primary or secondary emulsifier depending on use level). Formulations made with 0.4-1% HEMC were stable and had optimum viscosity, yield points and shear thinning behavior. And while the performance was not identical to that of carbomer (at the same use level), the HEMC outperformed commercial high molecular weight Hydroxyethyl Cellulose and provided rich, non-sticky, and non-stringy lotions and creams.
In specific applications, the suspension benefits provided by using HEMC are not sufficient. Blends with natural gums were explored as these materials can form networks that often provide suspension. The RM combination (HEMC and Xanthan Gum) enabled the formulation of clear and stable shampoos with a rich, smooth, and uniform texture that showed enhanced suspension properties compared to shampoos containing either RM on its own, or those thickened with salt. Such combinations are biodegradable alternatives to acrylic-based RMs and can deliver similar sensory and performance attributes.
Conclusion: The new cellulose-based HEMC product is a suitable RM for a wide range of hair and skin care formats. It provides optimum stability, viscosity, and sensory properties with a more sustainable profile than the current synthetic RMs. In addition, blends of the HEMC with natural gums were found to further enhance suspension properties.