Carbomer is a kind of polymer formed by chemical cross-linking of acrylic acid or acrylate with allyl ether, including polyacrylic acid (homopolymer) and long-chain alkyl alcohol acrylate polymer (copolymer). Its molecular structure contains 52 ~ 68% acid groups, so it has certain acidity and hydrophilicity, and can be soluble in water, ethanol and glycerol. Carbomer has the functions of thickening, suspending, stabilizing the system, regulating the release of water and active substances, and has simple process and good stability, so it is a kind of rheological modified thickener which is widely used in personal care products, pharmaceuticals and other fields.
There are two main thickening mechanisms of Carbomer, including neutralization thickening and hydrogen bond thickening.
- Neutralization and thickening
Because it contains certain acid groups, alkaline neutralization is needed in the process of application. The carboxyl group of the alkaline neutralized carbo resin is ionized. Due to the mutual repulsion of negative charges, the curled molecular chain extends in a state of great expansion, which increases the original volume to about 1000 times, thus plays a role in thickening. The commonly used neutralizers are sodium hydroxide, potassium hydroxide, potassium bicarbonate and triethanolamine (a glittering and translucent gel can be obtained when the pH is adjusted to about 7), which is why Carbomer is sensitive to ions.
- Hydrogen bond thickening
Carbomer, as a carboxyl donor, can combine with one or more hydroxyl groups to form hydrogen bonds and thicken. This reaction mechanism takes time. The commonly used hydroxyl donors are Nonionic surfactants, polyols and so on.
Performance and Application of Common Carbomer Series
According to the degree of cross-linking and molecular weight, Carbomer has a variety of products of different types, including traditional series of Carbopol 910,934,934p, 940,941,954, as well as new polymers such as Carbopol Ultrez 20 / 21. Different types of carbomers have different uses in different industries because of their different suspension stability and fluidity changes.
Traditional Carbomer
Appearance: White loose powder, slightly odor.
Properties: short rheology; medium and high viscosity; medium transparency, slightly yellow; low ion resistance; high shear resistance; suspension stability, high heat resistance.
Safety: possible residual solvents (benzene or xylene).
Application: suitable for high viscosity gel, lotion and ointment; suspension and emulsification; local application; skin care; hair care; taste masking; cream; hand, body and facial lotion. It is widely used in pharmaceutical (ointment) formulations and cosmetic creams.
Appearance: White loose powder, slightly odor.
Properties: (jelly) extremely short rheological property; high viscosity; high transparency; low ion resistance; low shear resistance; high yield value (suspension capacity).
Solubility: soluble in water, glycerol, ethanol, etc.
Safety: no mold will grow in dry state, non-toxic and non-irritating.
Application: it can provide the stability of oil-in-water emulsion system, which is suitable for emulsion and cream.
Recommended dosage: 0.2% ~ 1.5%.
Appearance: White loose powder, slightly odor.
Properties: (slug type) long rheology; low viscosity; high transparency; medium ion resistance; low shear resistance.
Solubility: soluble in water, glycerol, ethanol, etc.
Application: can produce low viscosity permanent emulsions and suspensions, or even ionic systems, resulting in good colloid transparency (more effective at low concentrations). Carbo 941 is used as a stabilizer for oil-in-water emulsion systems in the cosmetics industry, and 971 as a sustained-release agent in the pharmaceutical industry, suitable for transparent gels, water-alcohol gels and emulsion products.
Modified carbomer (no benzene).
Chemical name: cross-linked polyacrylic resin.
Appearance: White loose powder, slightly odor.
Properties: very short rheological property; high viscosity; high transparency; low ion resistance; low shear resistance; high yield value (suspension capacity).
Solubility: soluble in water, glycerol, ethanol, etc.
Application: suitable for thickening, suspension and emulsification in cosmetics or pharmaceutical formulations. Such as: setting gel, water alcohol gel, moisturizing gel, bath gel, toothpaste, shampoo, shaving gel, moisturizer and sunscreen, etc.
Dosage: 0.2% ~ 1.5%.
Chemical name: cross-linked polyacrylic resin.
Appearance: White loose powder.
Properties: long flow characteristics; medium viscosity; high transparency; high ion resistance; high shear resistance; high yield value (suspension capacity).
Solubility: soluble in water, glycerol, ethanol, etc.
Application: excellent rheological improver in the presence of electrolyte, polymerization and emulsification, suitable for aqueous solution or dispersion containing water-soluble salt.
Chemical name: acrylate / C10-30 alkyl acrylate cross-chain copolymer.
Appearance: White loose powder.
Properties: long rheology; medium viscosity; high transparency; high ion resistance; shear resistance; efficient thickening, strong suspension capacity.
Application: suitable for transparent gel, water-alcohol gel, surfactant system (special shampoo, cleaning products, etc.) and systems with high electrolyte content (such as aloe gel).
Recommended dosage: 0.2% ~ 1.5%.
- Carbopol AQUA SF-1.
A New Rheological modifier for liquid Acrylic Acid.
INCI name: acrylic acid (ester) copolymers.
Appearance: milky white to white liquid.
Properties: long rheology; high viscosity; medium transparency (opaque body, after adding the product); low ion resistance; high shear resistance.
Solubility: soluble in water, glycerol, ethanol, etc.
Application: can prepare clear formula, excellent compatibility with a variety of components, acid thickening, can be used in surfactant system.
- Carbopol Ultrez 20 (a new type of easily dispersed copolymer).
Chemical name: acrylate / C10-30 alkyl acrylate cross-chain copolymer.
Appearance: White loose powder.
Properties: long rheology; high transparency; medium viscosity; medium ion resistance; high shear resistance; easy dispersion, excellent and stable suspension ability.
Application: can be used in shampoo, bath gel, cream, lotion, hydrogel with high electrolyte. In addition, the U20 can also give the product a bright appearance, with better fluidity and tipping, providing the product with a smooth, light and soft touch.
The efficacy and function of Carbomer
- Protect the skin
Carbomer has an obvious protective effect on human skin, it has a certain affinity to human skin, usually, people add it to cosmetics, later use, can protect the skin, and can reduce irritating substances, stimulation and injury to human skin and skin mucosa, can prevent the occurrence of a variety of allergic symptoms.
- Anti-ultraviolet radiation
Carbomer has a certain activity after it is applied on the surface of human skin, it can enhance the resistance of human skin to ultraviolet rays and reduce the damage of ultraviolet rays to human skin. Carbomer’s sunscreen is added in the summer. It will play a particularly ideal sunscreen effect, can prevent the skin from blackening and can also prevent the skin from being burned by ultraviolet rays.
- Reduce viscosity
Carbomer has a certain degree of looseness, and it is a kind of slightly acidic substance with strong hygroscopicity. Usually, an appropriate amount of Aunt Han can be added when making gel or cosmetics, which can reduce the viscosity of these substances and maintain their stable properties. Carbomer is an important raw material for making cosmetics and gel in current industrial production.
- Anti-inflammation and sterilization
Carbomer is also a natural medicinal ingredient, which can reduce inflammation and sterilization. Carbomer eye drops sold on the pharmaceutical market are drugs made from it as the main raw material. It has a good effect on the elimination of human eye inflammation and can quickly relieve the pain and redness and swelling of the eyes.
- Ensure the quality of cosmetics
Carbomer is a chemical neutralizer, which plays a very important role in the production of cosmetics. It can integrate a variety of ingredients in cosmetics and keep them in a stable and appropriate state. And the cosmetics added with carbomer will have a good matrix, and people will feel very comfortable after applying it on the skin.
References
1. Singla, A. K., Chawla, M., & Singh, A. (2000). Potential applications of carbomer in oral mucoadhesive controlled drug delivery system: a review. Drug development and industrial pharmacy, 26(9), 913-924.
2. dos Santos, R. S., Rosseto, H. C., da Silva, J. B., Vecchi, C. F., Caetano, W., & Bruschi, M. L. (2020). The effect of carbomer 934P and different vegetable oils on physical stability, mechanical and rheological properties of emulsion-based systems containing propolis. Journal of Molecular Liquids, 112969.