Isooctyl Palmitate (2-Ethylhexyl Palmitate) - CAS 29806-73-3

Isooctyl Palmitate (2-Ethylhexyl Palmitate) - Properties, Applications, and Safety

Isooctyl palmitate (2-ethylhexyl palmitate, also known as octyl palmitate) is a branched-chain fatty acid ester synthesized from 2-ethylhexanol and palmitic acid. It is a clear, colorless to light yellow, low-viscosity liquid with a faint characteristic odor. This ester is widely used as a lightweight emollient and skin-feel modifier in cosmetic and personal care formulations, valued for its ability to spread easily, form a non-occlusive film on the skin, and provide a silky, lubricious feel without leaving a heavy or greasy residue.

Chemical and Physical Properties

Isooctyl palmitate has the molecular formula C₂₄H₄₈O₂ and a molecular weight of approximately 368.64 g/mol. The compound has a density of 0.850–0.865 g/mL at 20°C, a refractive index of 1.4445–1.4465, and a flash point of approximately 204°C. Its melting point is in the range of 2–6°C. The ester is practically insoluble in water and glycerin, but is miscible with oils, organic solvents, and many cosmetic ingredients. The saponification value is typically 145–155 mg KOH/g, and the acid value is less than 1.0.

Mechanism of Action

As an ester, isooctyl palmitate functions primarily as an emollient, skin conditioning agent, and pigment dispersant. It works by spreading rapidly on the skin surface, forming a thin, non-occlusive film that fills the spaces between skin cells, creating a smooth, soft, and flexible surface. Its branched-chain structure provides a lighter feel compared to straight-chain esters, contributing to its characteristic non-greasy, "dry" emollient effect. It also acts as a solvent and carrier for lipophilic active ingredients, fragrances, and pigments, improving their dispersion and uniformity in cosmetic formulations.

Applications

Isooctyl palmitate is a versatile ingredient with a wide range of applications across the cosmetic, personal care, and pharmaceutical industries.

Skin Care: It is a key component in moisturizers, body lotions, creams, sunscreens, and after-sun products. It provides a silky, smooth feel, improves spreadability, and enhances the absorption of active ingredients. It is often used as a non-occlusive emollient that does not leave a heavy residue.

Color Cosmetics: It serves as a pigment dispersant and binder in foundations, pressed powders, lipsticks, and blushes, ensuring even color distribution and smooth application.

Hair Care: It is used in conditioners and styling products to add shine, improve manageability, and reduce static.

Pharmaceuticals: It is used as a solvent, emollient, and carrying agent in topical formulations and transdermal delivery systems.

Industrial: It also finds use as a plasticizer and lubricant.

Safety and Toxicology

Isooctyl palmitate is considered a safe and well-tolerated ingredient for use in cosmetics and personal care products. The Cosmetic Ingredient Review (CIR) Expert Panel has concluded that ethylhexyl palmitate (and related esters) are safe as cosmetic ingredients. The panel's safety assessment was based on dermal, ocular, and toxicity studies showing no significant adverse effects at typical concentrations.

• Acute Oral Toxicity: The LD50 in rats is greater than 5 g/kg, indicating very low acute oral toxicity.

• Skin Irritation: The compound may cause mild skin irritation (H316), but is generally well-tolerated in cosmetic formulations at typical use levels.

• Environmental Impact: The EWG Skin Deep database rates octyl isopalmitate as having low concerns for cancer, allergies, developmental toxicity, and use restrictions.

• Comedogenicity: Limited evidence suggests it may have low to moderate comedogenic potential, meaning it could potentially clog pores in acne-prone individuals.

Storage and Handling

Isooctyl palmitate should be stored in tightly sealed containers at 5–25°C, protected from light, moisture, and strong oxidizing agents. It is stable under normal storage conditions and has a long shelf life. The product is not classified as a hazardous material under general safety reporting, but standard laboratory or industrial hygiene practices should be followed.