BOC Sciences

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

Carbopol 934 (benzene solvent homopolymer)

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.

Carbopol 940 (benzene solvent homopolymer)

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%.

Carbopol 941 / 971 (benzene solvent homopolymer).

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.