What is a Carbomer?

Alone, most carbomers are fluffy white powders.

A carbomer is a homopolymer of acrylic acid, which is cross-linked, or bonded, to any of several polyalcohol allylic polyethers. Usually appearing as a white powder, the compound is used as a thickener and emulsion stabilizer. Best known for its use in the cosmetics industry, it also has practical applications in medicine and hygiene. Many agencies consider the various types to be perfectly safe, although some of the substances used to neutralize their pH can be problematic.

Chemical and Physical Traits

Carbomers are common ingredients in shampoos and body cleansers.

Similar to other polymers, carbomers are made up of long chains of many repeating smaller molecules, which have a large number of bonds. Although the molecular weight varies based on the exact molecules found in the chain, it is typically relatively high. These compounds are capable of absorbing large amounts of water, increasing in volume up to 1,000 times in some cases, and can form stable, decay-resistant gels and thick solutions. Specifically, it is the polyalcohol moiety that gives the carbomer its high water solubility, unusual in polymers of this size. They are usually white powders when not added to a solution.

Marking

Carbomers are used in toothpastes.

Scientists are able to make different types of carbomers, each with a slightly different molecular structure. To keep these different types straight, they use a numerical suffix and capitalize the word as in a title or proper name, like Carbomer 940. Under this labeling system, the number indicates the average molecular weight of the polymer chains.

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forms

Carbomers can be used in denture cleaners.

Most commonly, companies use carbomers in cosmetics – in fact, they were created specifically for this industry. However, they also have several hygienic uses. They are used in toothpastes and gels, for example, as well as denture cleansers, and are common in shampoos. Many topical creams and lotions, such as those used to keep the skin hydrated or treat various skin conditions, also use them, and they are also found in certain types of eye drops. Another familiar product that uses them is disposable diapers – it’s these compounds that absorb water in the urine and make the diaper swell when wet.

reasons for use

Carbomers can be found in many lotions.

The consistency and texture of cosmetics and personal care products are of critical importance to the consumer, and different agents are routinely added to these products to control tactile qualities. Natural plant extracts or gums have been used but are generally not ideal as they can vary in quality from batch to batch. They can also cause allergic reactions in sensitive users and are often subject to bacterial attack and spoilage, requiring the addition of antibacterials.

Carbomers can be found in certain types of eye drops.

In contrast, a carbomer is an excellent thickening agent, is consistent from batch to batch, does not support bacterial growth, and is hypoallergenic. It also has a particularly pleasant “skin feel”, producing solutions and gels that are rich and luxurious to the touch. As an emulsion stabilizer, carbomers keep oils or creams suspended in water and prevent separation.

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Disposable diapers contain carbomer.

The size of these polymers and the way they are bonded allows them to function as net-like structures in water, allowing them to support fine, insoluble particles better than biologically derived gels and at lower concentrations. For this reason, people often think of them as suspending agents when they need to disperse fine solids in creams or lotions.

Safety

In general, regulatory agencies consider carbomers safe and have a history of use that spans at least five decades. They are included in the United States Pharmacopeia, and Carbomer 934P/974 has been approved for use in oral formulations and ophthalmic solutions, an indication of its low toxicity. The Environmental Working Group (EWG) also reports that they are not a concern in terms of bioaccumulation or risk to the environment. When at full strength, however, they have the potential to cause some eye and skin irritation; therefore, in most cases, manufacturers adjust their concentration.

Aqueous solutions of carbomer are mildly acidic, usually having a pH of about 3. Companies typically adjust the acidity of products containing these compounds with a base, such as triethanolamine, to bring it up to a more neutral value. Although the polymers themselves are generally not problematic if manufacturers adjust their strength appropriately, the substances used for neutralizing often have their own set of safety concerns. Reading the label does not always alert consumers to the presence of these neutralizers, depending on their classification and regulation.

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