Carbomer classification encompasses types like homopolymers (e.g., AC-Carbomer 940)and copolymers (e.g.,AC-Carbomer U20),with grades varying in key properties such as self-wetting time, where AC-Carbomer U21 leads at 1.5 minutes,compared to 60 minutes for 940,influencing their use in gels, lotions,and personal care products for optimal viscosity and ion resistance.

Types

Carbomer is an acrylic acid-based cross-linked polymer, widely used as a thickener and rheology modifier, which is indispensable in the cosmetics and personal care industry. Its classification is mainly based on the polymer structure, divided into two major types: homopolymers and copolymers.

Homopolymers (e.g., AC-Carbomer 940 and AC-Carbomer 980) are polymerized from a single monomer, featuring high viscosity and high transparency;

Copolymers (e.g., AC-Carbomer U20 and AC-Carbomer U21) are prepared via cross-polymerization of multiple monomers, with superior ionic resistance and broader formulation adaptability.

Chemical Structure

From the perspective of chemical structure, the INCI name of homopolymers is uniformly Carbomer, while copolymers are labeled as Acrylate/C10-30 Alkyl Acrylate Crosspolymer.

Homopolymers exhibit rheological properties of rapid swelling and instantaneous thickening, meaning they can thicken quickly and are suitable for products requiring immediate viscosity;

Copolymers possess characteristics of slow swelling and rheological stability, capable of providing more durable stability and shear resistance.

For example, AC-Carbomer 940 performs excellently in transparent gels because it can form a matrix with high viscosity and few bubbles, while AC-Carbomer U20 maintains its performance in formulations containing electrolytes and is not easy to degrade due to ionic interference.

The following is a summary table of Carbomer types and specifications

Rheological Properties

Rheological properties are the core factors distinguishing Carbomer types. Homopolymers such as 940 and 980 can achieve high viscosity at low pH or low concentrations, making them very suitable for formulations that require rapid thickening, such as hand sanitizing gels or hair styling gels.

Their short rheology means that once neutralized, the viscosity increases rapidly.

In contrast, copolymers such as U20 and U21 provide more controllable rheology. U20 shows optimal viscosity stability at pH=7.5 and 0.2% concentration, making it suitable for products with long-term storage requirements.

AC-Carbomer U20 has a higher viscosity than competing products, which can prevent stratification in emulsions, while the short rheology of U21 is suitable for high electrolyte environments, such as certain cleaning products where high ion content can easily damage ordinary thickeners.

AC-Carbomer U20 has a higher viscosity than competing products, which can effectively prevent stratification and creaming in oil-in-water (O/W) emulsions, while U20 and U21 exhibits excellent electrolyte tolerance due to its unique copolymer structure, making it suitable for high electrolyte environments, such as certain cleaning products where high ion content can easily damage ordinary thickeners.

Grades

The grading of Carbomer is not arbitrary. It is based on specific performance parameters and chemical structures, which directly affect its performance in cosmetics and personal care products. Simply put, the grade is like the "ID card" of Carbomer. Each grade code such as AC-Carbomer 940 or U20 represents a unique set of characteristics, such as thickening speed, ionic tolerance or skin feel.

For example, AC-Carbomer 940 is known for its high viscosity and transparency, making it suitable for high-end gel products, while AC-Carbomer U21 is preferred for large-scale production processes due to its rapid self-wetting ability.

Carbomer grades are mainly distinguished by key structural and performance parameters, including crosslinking density, molecular weight, self-wetting time, ionic resistance and shear resistance.

Self-Wetting Time

Self-wetting time refers to the speed at which Carbomer absorbs water and disperses. The shorter the time, the higher the processing efficiency — AC-Carbomer U21 only takes 1.5 minutes, while AC-Carbomer 940 takes 60 minutes, which directly affects the production cycle.

Ion resistance determines the stability of the product in a salt-containing environment.AC-Carbomer U20 performs extremely well, making it suitable as a raw material for sunscreen or cleaning products. AC-Carbomer U21 and AC-Carbomer 980 have slightly inferior performance compared to AC-Carbomer U20, while AC-Carbomer 940 is at a medium level.

Shear resistance is related to processing tolerance. AC-Carbomer 940 and 980 are better and can withstand stirring or pumping pressure.

For a more intuitive understanding, the following is a table of key parameters for Carbomer grades:

Ionic Tolerance

Ionic tolerance is an important indicator for evaluating Carbomer grades, especially when the formulation contains electrolytes.

Tests were conducted under the condition of 0.1% wt NaCl, showing significant differences in the performance of different grades.

AC-Carbomer U20 can maintain high viscosity, which is crucial for product stability;

AC-Carbomer U21 and 980 is relatively weak and may not be suitable for high-ion environments.

Shear Resistance

Another key point is shear resistance, which describes the durability of the grade during processing.

AC-Carbomer 940 performs best and is suitable for high-shear applications such as pumping systems, while AC-Carbomer U21 is slightly weaker and requires careful handling.

This difference stems from the polymer structure — homopolymers such as 940 are usually more stable, while copolymers such as U20 balance flexibility and performance.

• Self-Wetting Advantages: Grades such as U21 and U20 have short self-wetting times, can disperse      quickly, reduce agglomeration, and improve transparency.

• Viscosity Characteristics: At pH=7.5 and 0.2% concentration, AC-Carbomer U20 has the highest and most      stable viscosity, making it suitable for products that require long-term      storage.

• Application Flexibility: High-grade products such as 980 are suitable for a variety of pH      environments, while U20 is specially designed for high electrolytes,      expanding the formulation range.

Skin Feel and User Experience

AC-Carbomer 940 provides a balanced and refreshing feel, suitable for daily skin care products;

AC-Carbomer U20 imparts a luxurious and thick texture, commonly found in high-end emulsions; while the refreshing and non-greasy characteristics of AC-Carbomer U21 make it an ideal choice for cleaning products.

Documents show that these differences directly affect consumer preferences. For example, in shampoos, the elastic texture of U20 can enhance user satisfaction.

Application Scenarios

Personal Care Products

Taking AC-Carbomer 940 as an example, its high transparency and rapid thickening characteristics make it the first choice for transparent gel products.

When preparing alcohol-containing hand sanitizing gels, 940 can form a crystal-clear matrix under neutral pH conditions with very few bubbles, which is particularly important for high-end brands that focus on appearance.

In contrast, AC-Carbomer 980 maintains high viscosity even in low pH environments, making it especially suitable for emulsions in acidic systems, such as certain vitamin C serums, where the pH value needs to be maintained at a low level to keep the active ingredients stable.

Hair Care Field

The long rheological properties of AC-Carbomer U20 make it an ideal choice for styling gels, as it can withstand the shear force caused by repeated combing without stratification.

For shampoos containing electrolytes, U21 exhibits excellent ion resistance and can maintain stable viscosity even in high-salt formulations.

Sunscreen Products

AC-SF-1, as a special copolymer, has excellent solubility in systems containing alcohol and glycol solvents.

When preparing sunscreen emulsions with high SPF values, its compatibility with inorganic sunscreens such as titanium dioxide can effectively prevent particle sedimentation.

This type of Carbomer can still maintain a delicate texture in formulations with an ethanol content of up to 30%, which is difficult for ordinary thickeners to achieve.

The following is a performance comparison table of various Carbomer models in different application scenarios:

In formulation practice, the addition order of Carbomer and neutralization process are also crucial.

Taking the preparation of hand cream as an example:

• First, disperse AC-Carbomer 980 in room temperature water to      avoid agglomeration

• Add emulsifier and oil phase, then homogenize

• Finally, neutralize to pH=7.0-7.5 with triethanolamine

This process can ensure a silky and non-greasy texture, which is the source of the "moisturizing and smooth" skin feel emphasized in the document.

For the emerging transparent shampoo market, the combined use of AC-Carbomer U20 and U21 shows unique advantages.The combination of U20 and U21 results in a moderate viscosity, enabling the stable suspension of pearlescent pigments and with an extremely low residue, while U20’s excellent ionic tolerance enhances transparency and system stability in formulations containing cationic conditioning agents.

• Sensitive Skin Products:      Priority should be given to AC-Carbomer 980, whose mild characteristics      are suitable for repairing creams

• Children's Products: U21 is      recommended because its rapid dispersion characteristic can avoid thermal      damage caused by long-term stirring

• Organic Formulations: AC-SF-1      has better compatibility with plant extracts

• Products for High-Temperature Environments: The shear stability of 940 can prevent viscosity changes      during transportation