All natural, aqueous-based polymeric thickeners are derived from polysaccharides with the most common being sourced from cellulose (wood, cotton) and starch(corn, potato). Other important polysaccharide sources include seaweed, plant seeds/roots, and those derived from fermentation. Most natural-based thickeners are either soluble or swellable polymers that bind or immobilize water to create structure or viscosity.
Cellulosicsare the most commercially important and diverse class of natural-based thickeners with numerous anionic, cationic, and nonionic versions available. All derivatives are produced by first solubilizing cellulose with sodium hydroxide and then reacting with the functionalizing chemical.
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Carboxymethylcellulose (CMC) is one of the most important and cost effective natural-based thickeners on the market. It is an anionic polymer produced by reacting alkali cellulose with chloroacetic acid. Key properties are determined by the MW of the cellulose (high-700K, medium 250K, low-90K) and the degree of carboxylation per glucose molecule (DS-theoretical is 3). CMC can be either a soluble or swollen polymer or a combination depending on the MW and DS. Salt sensitivity is reduced using a low MW and high DS grade. The most thixotropic, viscous grades have a high MW and low DS.
Nonionic grades are produced by reacting alkali cellulose with ethylene oxide(hydroxyethylcellulose) or propylene oxide (hydroxypropylcellulose). Hydroxypropylmethylcellulose is made by first reacting the alkali cellulose with methyl chloride and then propylene oxide. Nonionic cellulosics are useful in formulations because they have excellent cationic, salt, PH tolerance and solvent tolerance. Some, like hydroxypropylcellulose, are also good thickeners for solvents like ethanol.
Starch derivatives are not commonly used in personal care. Many have poor viscosity stability over time. Hydroxypropyl starch phosphate is the only significant starch derivative used.
Xanthan is an anionic, fermentation-derived, polysaccharide that is widely used in cosmetics. Xanthan has an MW of 2-3 million Daltons and forms a double helical structure in most ionic solutions. Xanthan was discovered by the United States Department of Agriculture and commercialized in 1964 by CP Kelco. The key benefits of Xanthan include good salt/PH tolerance, high viscosity at low concentration, and the ability to maintain its viscosity profile at elevated temperatures.
Carrageenan is the most important seaweed-derived thickener used in personal care products. It is a sulfated, anionic polysaccharide that exists in three forms; Kappa, which has 1 sulfate group per galactose molecule, Iota- 2 sulfate groups, and Lamba-3 sulfate groups. Only the Iota form is widely used as a thickener.
Plant seed/root-based thickeners are widely used in foods but not in personal care formulations. The most significant materials are konjac mannan, locust bean, guar, and tara gum. These are galactomannans that react synergistically to build viscosity when combined with xanthan.
Cellulosic/starch thickeners (naturally derived/modified)
- Aqualon 7H4 (Cellulose Gum) by Ashland is a low DS, high viscosity grade. A 1% dispersion has a viscosity of 2,500-6,000 cps.
- Natrosol 250 HR/HHR Hydroxyethylcellulose, PC Grade (Hydroxyethylcellulose) by Ashland – A 1% dispersion has a viscosity of 3,400-5,000 cps.
- Methocel 40-202 (Hydroxypropyl Methylcellulose) by Dow Chemical – A 2% dispersion has a viscosity of 4,000 cps.
- Klucel Hydroxypropylcellulose, CS Grade Type H (Hydroxypropylcellulose) by Ashland – A 1% dispersion has a viscosity of 1,500-3000cps), can gel Ethanol
- Natrosol Plus 330 CS Cetyl (Cetyl Hydroxyethylcellulose) by Ashland is a hydrophobic ally modified grade that can dramatically increase the viscosity of some o/w lamellar gel network based formulations. A 1% solution has a viscosity of 400 cps.
- Avicel RC 591 (Microcrystalline Cellulose, Cellulose gum) by FMC is a 90% mixture of microcrystalline cellulose and CMC. The material forms extremely stable, thixotropic colloidal gels when dispersed in water using high shear.
- Structure XL (Hydroxypropyl Starch Phosphate) by Akzo Nobel is a specially processed pre-gelatinized starch that disperses in cold water instantly without requiring sifting or premixing. A 4.5% dispersion has a viscosity of 2,000-7,000 cps and gels are salt stable.
Fermentation-based polysaccharide thickeners (all natural)
- Keltrol Advanced Performance (Xanthan) by CP Kelco is much easier to hydrate in difficult media, even in the presence of solvent or salt. Better for suspending solids in thin dispersions than regular grade xanthan. A 1% solution has a viscosity of 13K cps.
- Keltrol CG (Xanthan) by CP Kelco – A 1% solution has a viscosity of 1200-1600 cps in 1% potassium chloride.
- Amaze XT (Dehydoxanthan) by Akzo Nobel is a specially-processed xanthan gum that has significantly higher viscosity than normal grades. It, however, has reduced electrolyte tolerance. A 1% solution has a viscosity of 38K cps and 10K cps with 3% salt. It forms clear solutions.
- Actigum CS-11 QD (Scleroglucan) by Cargill is a fermentation produced polysaccharide that is nonionic, salt and high/low PH stable. Actigum, like xanthan gum, doesn’t lose viscosity at elevated temperature and has a high yield value. A 1% solution has a viscosity of 2-5K cps, 2% 61k cps.
Seaweed-based polysaccharide thickeners (all natural)
- Genuvisco TPC-1 (Carrageenan) by CP Kelco is an Iota form of carrageenan designed for cold processing that is stable over a PH of 4.5-11. The processed viscosity is low until electrolyte is added. A 1% gel has a viscosity of 18K with 3% salt added.
- Gelcarin GP 379 (Carrageenan) by FMC is an Iota form of carrageenan that rapidly hydrates at RT. A 1% gel in water has a viscosity of 32K cps without salt and a 2% gel 27k with 3% salt.
Plant seed/root-based polysaccharide thickeners (all natural)
- Propol A (Mannan) by Shimizu Chemical is a highly purified galactomannan derived from konjac flour. A 1% gel has a viscosity of around 50k cps with or without 3% sodium chloride, is stable at a PH of 3-9, and has an excellent skin feel.
- Solagum Tara (Caesalpinia Spinosa Gum (Tara gum)) by Seppic is a nonionic GRAS polysaccharide that forms electrolyte stable gels. The gels have a non-sticky, smooth feel and the materials quickly hydrate in cold water. A 1% solution in water has a viscosity of 3100-4500 cps and is significantly less stringy and thicker than a 1% xanthan solution.
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