A thickener is a substance that increases the viscosity of a liquid without significantly altering its other properties and is commonly used in cosmetics. Thickeners can also improve the suspension of other ingredients or emulsions, thereby increasing the stability of the product. Some thickeners are gelling agents, forming gels that dissolve in the liquid phase as a colloidal mixture, creating a weakly cohesive internal structure. Others act as mechanical thixotropic additives, having discrete particles that adhere or interlock to resist strain.
Thickeners used in cosmetics include synthetic polymers such as polyethylene glycol and other viscous liquids and vegetable gums. Some thickeners are also used as stabilizers when used to maintain the stability of emulsions. Some emollients, such as petrolatum and various waxes, can also be used as thickeners in emulsions.
All natural thickeners for water-based polymers are derived from polysaccharides, most commonly cellulose (wood, cotton) and starch (corn, potato). Other important sources of polysaccharides include algae, plant seeds/roots, and those produced by fermentation. Most natural-based thickeners are soluble or swellable polymers that bind or hold water to create structure or viscosity.
Cellulosics are the most important commercial class of natural-based thickeners and are available in a variety of anionic, cationic and nonionic forms. All derivatives are produced by first solubilizing cellulose with sodium hydroxide and then reacting it with functional chemicals.
Carboxymethyl cellulose (CMC) is one of the most important and cost effective natural thickeners on the market. It is an anionic polymer made by reacting basic cellulose with chloroacetic acid.
Xanthan gum is an anionic, fermentation-derived polysaccharide that is widely used in cosmetics. Xanthan gum has a molecular weight of 2-3 million daltons and forms a double helix structure in most ionic solutions. Xanthan gum was discovered by the US Department of Agriculture and commercialized by CP Kelco in 1964. Key benefits of xanthan gum include good salt / PH tolerance, high viscosity at low concentrations and the ability to maintain its viscosity profile at high temperatures.
Xanthan gum is the most important seaweed-derived thickener for personal care products. It is a sulfated, anionic polysaccharide that exists in three forms. Each galactose molecule has 1 sulfate group, 2 sulfate groups and 3 sulfate groups.
Thickeners are ubiquitous in life and are used not only in cosmetics, but also in food and household products. Thickeners can increase the viscosity of skin care products, improve their stability, and also change the logistics of skin care products, which simply means that they can make skin care products stickier. The benefit of this is that it allows skin care products to stay on the skin better, as they can easily run off if they are too watery. Of course, thickeners can make skin care products look thicker, which can also create an "illusion" of being rich in nutrients to consumers. Many lotions, creams, masks, and gels are almost always thickened with thickeners.