Polyoxypropylene stearyl ether
[CAS 25231-21-4]

Identification

• Classification: Chemical reagent >> Organic reagent >> Ether
• Name: Polyoxypropylene stearyl ether
• CAS Registry Number: 25231-21-4
• EC Number: 607-655-7
• SMILES: O(CC(O)C)CCCCCCCCCCCCCCCCCC

Safety Data

• Hazard Symbols: GHS07 Warning
• Risk Statements: H319
• Safety Statements: P264-P280-P305+P351+P338-P337+P313

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Eye irritation	Eye Irrit.	2	H319

chemBlink Chemical Story

A cosmetic emollient does not need to be a natural oil to make a surface feel less dry or less sticky. Polyoxypropylene stearyl ether, commonly represented by the INCI names PPG-11 Stearyl Ether or PPG-15 Stearyl Ether, is a useful example of a synthetic oil-compatible polyether designed mainly for feel, spreading, and formulation behavior.

The structure begins with stearyl alcohol, whose C18 hydrocarbon chain is strongly lipophilic. Onto that alcohol is built a polyoxypropylene chain. Propylene-oxide units contain ether oxygens, but they also carry methyl groups, making polyoxypropylene much more oil-compatible than the more strongly hydrophilic polyethylene glycol chain familiar from PEG surfactants. The result is a molecule that can dissolve in oily phases while still containing a flexible polyether segment.

That combination helps explain its role as an emollient. On skin or hair, oil-compatible molecules can fill microscopic gaps, reduce roughness, improve slip, and change how a formulation spreads. PPG stearyl ethers can also act as solvents for other hydrophobic ingredients and modify the sensory character of creams, antiperspirants, and other personal-care products. The chemistry is less about forming a dramatic new bond and more about engineering friction, wetting, and phase compatibility at a surface.

The number in names such as PPG-11 is an average degree of propoxylation. Commercial material is therefore not one single molecular mass but a distribution of chains centered around that average. CAS 25231-21-4 is used for PPG stearyl ethers of this general family, including records associated with PPG-11 and PPG-15. That is another example of why polymeric cosmetic ingredients should not be interpreted as perfectly monodisperse small molecules.

Safety assessments by the Cosmetic Ingredient Review Expert Panel examined PPG-11 and PPG-15 Stearyl Ether and reaffirmed that they are safe in cosmetics under the practices of use and concentrations described in the assessment. Such reviews matter because an ingredient selected for sensory benefits must still be evaluated for irritation, sensitization, and exposure in the real formulations where it is used.

Polyoxypropylene stearyl ether is memorable because it shows that "skin feel" has molecular chemistry behind it. A long hydrocarbon anchor supplies oil affinity; a flexible propoxy chain changes fluidity and spreading. By adjusting chain architecture rather than adding an active drug, formulators can make a product feel smoother, less greasy, easier to spread, or better able to carry other ingredients.

References:
1. FDA Global Substance Registration System, Polypropylene Glycol 11 Stearyl Ether, CAS 25231-21-4.
2. Cosmetic Ingredient Review. Safety Assessment of PPG-11 and PPG-15 Stearyl Ether. International Journal of Toxicology. 2023.
3. Final Report on the Safety Assessment of PPG-11 and PPG-15 Stearyl Ethers. International Journal of Toxicology. 2001/2002.
4. European cosmetic ingredient records for PPG-11 Stearyl Ether, function: emollient.

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