Ethylhexyl Stearate - Emollient Ester CAS 22047-49-0
Ethylhexyl Stearate (2-Ethylhexyl Stearate) - Properties, Applications, and Safety
2-Ethylhexyl stearate (CAS 22047-49-0), also known as octyl stearate or isooctyl stearate, is a branched, fully saturated fatty acid ester synthesized via esterification of stearic acid with 2-ethylhexanol. It is a clear, colorless to slightly yellowish liquid at ambient temperature with a faint characteristic odor. This ester is widely used in cosmetic and personal care formulations as a lightweight emollient, solvent, lubricant, and plasticizer.
Chemical and Physical Properties
2-Ethylhexyl stearate has the molecular formula C₂₆H₅₂O₂ and a molecular weight of 396.69 g/mol. The compound has a density of approximately 0.86 g/cm³, a boiling point of 431.9-438.7°C, and a flash point of 206-225.6°C. The acid value is typically ≤0.5 mg KOH/mg, the saponification value is in the range of 135-155 mg KOH/g, and the cloud point is ≤10°C. The compound is insoluble in water but soluble in oils and organic solvents. It is a medium-spreading, non-occlusive emollient with low comedogenicity. The kinematic viscosity is approximately 9.6 cST at 40°C.
Mechanism of Action
As an emollient, 2-ethylhexyl stearate forms a thin, non-greasy, lubricious film on the skin's surface, helping to reduce water loss and giving the skin a soft, smooth appearance. It reduces friction between surfaces, making it useful in formulations requiring smooth application. As a solvent and solubilizer, it can dissolve lipophilic ingredients, fragrances, and UV filters, improving their dispersion and uniformity in formulations.
Applications
Skin Care: 2-Ethylhexyl stearate is used in creams, lotions, moisturizers, and facial care products as a sensory emollient with low irritation and good lubricity. It provides a smooth, non-greasy after-feel and enhances product spreadability.
Sunscreens: Due to its compatibility with UV filters, it is recommended for use in sunscreen formulations. It does not shift the wavelength of maximum ultraviolet absorbance.
Color Cosmetics: Used in foundations, lipsticks, and eyebrow pencils as a pigment dispersant and binder.
Hair Care: Included in conditioners and styling products to add shine and improve manageability.
Industrial: Serves as a plasticizer in flexible PVC, an external lubricant in plastics, and a lubricant in metalworking fluids.
Safety and Toxicology
The Cosmetic Ingredient Review (CIR) Expert Panel has assessed stearate esters extensively and concluded that ethylhexyl stearate is safe for use in cosmetics, whether used in high or low concentrations. The compound is considered to have low irritation potential and is generally non-sensitizing. It is also clinically proven to have skin cell penetration properties and can be used as a carrier agent for other ingredients. However, it may be mildly comedogenic for acne-prone skin depending on the formulation. The EWG Toxcast analysis scored the compound at 2.5-3.5.
Storage and Handling
2-Ethylhexyl stearate should be stored in tightly closed containers under dry conditions, away from direct heat and light exposure. The shelf life is typically 24 months from the date of manufacturing when stored under recommended conditions.