Carbomer properties:

Carbopol is a white, loose, hygroscopic powder with a special odor and strong electrostatic effect. Because its structure contains 52%-68% carboxylic acid groups, it has a certain acidity. Its average particle size is 0.2um, its relative density is 1.4, and its average moisture content is 8%. It will not grow mold in a dry state. Soluble in ethanol, water and glycerin, it has the characteristics of a colloidal solution. Carbomer is a commonly used thickening agent in cosmetics. Carbomer thickening has certain requirements on the pH value of the system. If the pH value is lower or higher, the viscosity of the carbomer system will decrease.

Carbomer Features: 

1. Prolonged stirring or high shear stirring will cause viscosity loss or even permanent loss. 

2. Presence of ions-electrolytes will reduce thickening efficiency. 

3. It is not affected by temperature, does not support the growth of bacteria and mold, and does not have surfactant properties. 

4. Ultraviolet irradiation will reduce the viscosity and cannot be restored. Adding antioxidants can slow down the reaction. 

5. If you are afraid of salt, you cannot add mineral ions, otherwise the consistency will disappear and irritate the eye mucosa.

Carbomer thickening mechanism: 

1. Neutralize and thicken

Since it contains certain acid groups, alkaline neutralization is required during application. After being neutralized by alkaline, the carboxyl groups of the carboxy resin are ionized. Due to the mutual repulsion of negative charges, the curled molecular chains stretch into a state of great expansion, increasing the original volume to about 1,000 times, thereby causing to the thickening effect. 

2.Hydrogen bond thickening

As a carboxyl donor, carbomer molecules can combine with one or more hydroxyl groups to form hydrogen bonds and thicken. This reaction mechanism takes time. Commonly used hydroxyl donors include nonionic surfactants, polyols, etc. The neutralizing agent for carbomer can be sodium hydroxide, potassium hydroxide, potassium bicarbonate, borax, amino acids, and polar organic amines such as triethanolamine. Laurylamine and stearylamine can be used as neutralizing agents in non-polar systems. The neutralized carbomer hydrogel is most viscous between pH 6 and 11. If pH < 3 or pH > 12, the viscosity will decrease. The normal dosage is 0.2-0.4%, which can replace 3-7% of conventional emulsifiers.

Carbomer uses:

(1) Effective at a very low concentration - 0.1-0.5%, replacing the traditional surfactant dosage of 3-7%.

(2) Not limited by HLB value and PLT.

(3) It can emulsify any liquid oil at room temperature.

(4) If the wax is melted during manufacturing, the wax can be emulsified. 

(5) Give full play to the wetting, dispersing, adhesion and other functions of surfactants to produce stable emulsions. 

(6) It will not re-emulsify when re-wetting, making it easy to prepare waterproof emulsions without film-forming agents.

(7) The high oil phase can be dissolved into water to form an (o/w) emulsion. 

Carbopol is a copolymer of polyalkyl sucrose or polyalkyl pentaerythritol and acrylic acid cross-polymer. Different materials and degrees of polymerization constitute products of various specifications, such as Carbopol 910, 934, 934p, 940, 941, 954, 971P, 980, 981 and Carbopol 1342, 1382, 2984, 5984, etc.

Commonly used carbomer series:

Carbopol 940: short rheology, high viscosity, high clarity, low ionic resistance and shear resistance, suitable for gels and creams.

Carbopol 941: long rheology, low viscosity, high clarity, medium ionic resistance and shear resistance, suitable for gels and emulsions. 

Carbopol 934: cross-linked polyacrylic resin, topical drug delivery system, stable at high viscosity, used in concentrated gels, emulsions, and suspensions.

Carbopol 1342: cross-linked polyacrylic resin, topical drug delivery system, excellent rheology modifier in the presence of electrolytes, polymeric emulsification.

Carbopol 980: cross-linked polyacrylic resin, topical delivery system, crystal clear gel, water or alcohol solvent.

Carbopol ETD 2020: Acrylate/C10-30 alkyl acrylate cross-chain copolymer, long rheology, low viscosity, high clarity, high ionic resistance and shear resistance, suitable for clear gels. For high molecular polymers, the larger the number followed (such as Carbomer 940), the larger the polymer molecule.