Carbomer Basics: How It Works and Applications

Follow the basics of how carbomer forms gels, how neutralization affects texture and where it is used. For a comparison of Carbomer 940, 980, U20 and U21, see the carbomer types and grades guide. For cosmetic-grade ingredient specifications, review the ANECO Carbomer Series.

Carbomer is a fundamental thickening agent in cosmetics that works by absorbing water and expanding into a clear gel when neutralized.

Key variants like AC-Carbomer U21 wet in just 1.5 minutes for easy mixing, while others like AC-Carbomer U20 and U21 offer strong ion resistance for stable formulas containing salts.

These polymers are essential for creating everything from transparent gels and lotions to shampoos, providing controllable texture from light to rich feels.

Basic Knowledge

When we unscrew a bottle of transparent gel or scoop out a spoonful of rich cream, we rarely think about what gives them such wonderful textures.

The unsung hero behind this is often a key ingredient called Carbomer.

In the world of cosmetics, it's like the steel reinforcement in an architect's hands—not necessarily the main focus, but the cornerstone that builds the product's structure and determines its texture.

Simply put, Carbomer is a highly efficient rheology modifier whose main functions are thickening, suspending, and stabilizing formulations, allowing skin care products, hair care products, and personal care products to take on the various forms we love.

From a chemical perspective, Carbomer is not a single substance but a family of polymers.

You can imagine it as a three-dimensional fishing net composed of countless acrylic acid units connected together, with numerous "grabbing hands" (carboxyl groups). The size and density of the net's mesh determine the different characteristics of different Carbomer grades.

Based on differences in monomers and structures, Carbomers are mainly divided into two categories:

How It Works

Carbomer is a high-molecular-weight polymer polymerized from acrylic acid. Its molecular chains are like a mess of threads connected by crosslinking agents to form a huge three-dimensional network structure. This structure is tightly contracted, but it has a powerful ability: to capture water molecules.

When Carbomer powder is dispersed in water, its dry molecular chains begin to absorb water and expand, but at this stage, it cannot form a viscous gel, and the viscosity is very low.

The molecular chains of Carbomer are covered with carboxyl groups (-COOH). When a neutralizing agent (such as triethanolamine, sodium hydroxide) is added, these carboxyl groups ionize into negatively charged carboxylate ions (-COO⁻).

Due to mutual repulsion of like charges, these negatively charged groups repel each other, forcing the originally curled molecular chains to fully stretch and occupy a huge space.

At the same time, water molecules are firmly locked in this suddenly expanded network, which macroscopically manifests as a sharp increase in viscosity, forming a clear and stable gel.

Carbomer's excellence is reflected in several key characteristics:

Self-wetting and Dispersion Ability

If the powder clumps in water to form hard-to-disperse "fish eyes", the subsequent thickening effect will be greatly reduced. Different Carbomer grades vary significantly in this regard. For example, AC-Carbomer U21 and U20 have extremely fast self-wetting speeds due to their special molecular design.

U21 and U20 can complete wetting in a few minutes, which means that in production, the stirring time can be greatly shortened, efficiency improved, and the risk of product quality problems caused by uneven dispersion reduced.

Their rapid self-wetting characteristic makes them very suitable for formulations that require rapid production or have high process tolerance requirements.

Ion Resistance

Many cosmetic formulations contain electrolytes, such as salts, certain active ingredients, or pH adjusters.

These charged ions can interfere with the electrostatic repulsion between Carbomer molecular chains, just like inserting many "buffers" into the neutralized Carbomer network, preventing the network structure from fully expanding, thereby causing a decrease in viscosity and even water separation.

Therefore, for formulations containing electrolytes (such as certain emulsions, sunscreen products, or gels with specific ingredients), it is crucial to select Carbomers with high ion resistance.

Tests have shown that under 0.1%wt NaCl conditions, different Carbomers have different ion resistance performances: AC-Carbomer U20 and 980 show strong ion resistance, while AC-Carbomer 940 has moderate ion resistance, and U21 is relatively weak.

Rheological Properties

Rheological properties refer to the deformation and flow behavior of a product when subjected to force. This directly affects the product's skin feel. Carbomers mainly provide two types of rheology:

• Short Rheology (Pseudoplastic Fluid): Representative products include AC-Carbomer 940, 980, and  U21. Such gels are very viscous when at rest, but once subjected to shear  force (such as application, pumping), the viscosity drops rapidly, making  them easy to spread, with a fresh and non-greasy skin  feel after use.

• Long Rheology (Viscoelastic Fluid): Representative product is AC-Carbomer U20. Its viscosity  decreases slowly when subjected to shear, providing a rich and luxurious  cream texture, and leaving a plump and elastic film feel  after application.

In addition, shear resistance is also an important indicator, which measures the ability of Carbomer gel to maintain its structure without being destroyed during processing such as high-speed stirring and pumping. Generally, the shear resistance of AC-Carbomer 940 and 980 is better than that of U20 and U21.

Applications

Carbomer has an extremely wide range of applications, from daily facial creams and body washes to professional hair styling products.

The following table clearly shows the classic application scenarios of different Carbomer grades:

In the field of transparent gels, AC-Carbomer 940 and 980 are well-deserved stars.

They can provide extremely high viscosity and unparalleled transparency, making them very suitable for making visually appealing transparent gel products, such as popular hand sanitizers, refreshing sleeping masks, or hair styling gels.

Because these products usually contain alcohol, they require Carbomer to stably thicken in alcohol-based systems, which 940 and 980 are exactly capable of. Their controllable rheological properties can bring a smooth application feel.

When the formulation becomes more complex, such as containing salts, certain active ingredients, or specific preservatives, the challenge of electrolytes arises.

The advantages of AC-Carbomer U20 and U21 become prominent. They are inherently more ion-resistant, able to resist viscosity loss caused by electrolytes, ensuring that the product maintains a stable state throughout its shelf life.

U20 can provide a luxurious and rich skin feel, making it very suitable for high-end emulsions and creams; while U21 is more inclined to a fresh and non-greasy skin feel, making it an ideal choice for making sunscreens, refreshing moisturizing gels, and products that require high electrolyte content.

Their rapid self-wetting characteristic also makes the production process more efficient.