Can Natural Polymers Replace Synthetic Carbomers?*

Carbomers are versatile and stable rheology modifiers but are synthetic and cannot be formulated in a natural-claimed product. This study focused on replacing carbomers using combinations of natural polymers of the polysaccharide type.
Carbomers are versatile and stable rheology modifiers but are synthetic and cannot be formulated in a natural-claimed product. This study focused on replacing carbomers using combinations of natural polymers of the polysaccharide type.
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*A portion of this paper was first presented during the IFSCC 2020 Congress.

Read the full feature in the July/August 2022 digital edition here. . .

There is pressure on cosmetic formulators to find suitable replacements for synthetic and semi-synthetic cosmetic ingredients, and to develop products that could be marketed as natural. One of the most prominent examples is carbomer, a representative of an extensively used category of poly(acrylic acid) polymers.

The present study attempts to replicate the rheological and sensory properties of carbomer using natural polymers of the polysaccharide type. Polysaccharides are carbohydrate biopolymer structures formed by the condensation polymerization of repeating units of monosaccharides and disaccharides, and joined by glycosidic bonds. The terms gums or hydrocolloids are often used interchangeably when referring to polysaccharides of vegetable or biotechnological origin.1 While all hydrocolloids have the property to form viscous dispersions in water, some of them also form gels. Hence, the food industry, and especially the cosmetic industry, make a distinction between thickeners and gelling agents.2

The mechanism of thickeners involves a non-specific entanglement of conformationally disordered polymer chains.2 The viscosity of the dispersion is influenced by the polysaccharide hydrodynamic volume, which increases with molecular mass, chain rigidity and electrostatic charge density, and is greater for linear as opposed to a branched structure.3 Examples of natural thickening agents are xanthan gum, konjac gum, guar gum and cellulose derivatives.

In the gelling process, there is an additional step—the formation of junction zones. In the case of hydrocolloids, they are created by the physical association of their polymer chains through hydrogen and hydrophobic bonds and cation-mediated cross-linking.4 This process forms a three-dimensional network, which immobilizes water and creates a rigid structure resistant to flow. Examples of natural gelling agents include carrageenan, gellan gum, pectin and alginate. The textural properties (e.g., elastic or brittle) of a gel vary widely with the type of hydrocolloid used.

As opposed to the described physical gels, carbomer forms a more stable chemical gel at much lower concentrations due to the permanent cross-linking of its poly(acrylic acid) chains.5 Being a weak polymeric acid, carbomer requires the addition of a base to ionize the carboxylic acid groups, which causes the creation of negative charges along the polymer backbone and the uncoiling of the chains due to electrostatic repulsion.

Considering the various mechanisms among these material types, as stated, the present study aimed to assess whether it is possible to replace a synthetic polymer carbomer with one or more natural hydrocolloids of the polysaccharide type in cosmetic emulsions. Rheological, textural and sensory methods were employed to evaluate the effectiveness of the replacement.

. . .Read more in the July/August 2022 digital edition here. . .

Acknowledgments: The authors wish to acknowledge the contribution of Yogesh Solanki to the experimental part of this work and CP Kelco UK for generously supplying polysaccharides used in the study.

References

  1. Sworn, G. (2004). Hydrocolloid thickeners and their applications. Gums and Stabilizers for the Food Industry 12 13-22. RSC Publishing, Oxford.
  2. Phillips, G. and Williams, P. (2000). Introduction to food hydrocolloids. Handbook of Hydrocolloids 1-22. CRC Press, Boca Raton.
  3. Saha, D. and Bhattacharya, S. (2010). Hydrocolloids as thickening and gelling agents in food: A critical review. J Food Sci Tech 47(6) 587-597.
  4. BeMiller, J.N. (2008). Hydrocolloids. Gluten-free Cereal Products and Beverages. 203-215. Academic Press.
  5. Tamburic, S. and Craig, D.Q.M. (1995). Rheological evaluation of polyacrylic acid hydrogels. J Pharm Pharmacol 1(3) 107-109.
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