PEG-4 Laurate (Poly(oxy-1,2-ethanediyl), .alpha.-(1-oxododecyl)-.omega.-hydroxy- (4 mol EO average molar ratio)) is a synthetic compound created by the esterification of lauric acid with polyethylene glycol (PEG-4). It is primarily used as an emulsifier and surfactant in cosmetic formulations, known for its ability to improve product texture and stability.

Chemical Composition and Structure

The chemical composition of PEG-4 Laurate includes:

• Lauric Acid: A medium-chain fatty acid derived from coconut oil or palm kernel oil, providing moisturizing and emollient properties.
• Polyethylene Glycol (PEG-4): A polymer that enhances emulsifying properties and improves the solubility of the formulation.

Structurally, PEG-4 Laurate consists of lauric acid chains attached to PEG-4, allowing it to effectively function as an emulsifier in various cosmetic formulations.

Physical Properties

• Appearance: Typically a clear to slightly yellow viscous liquid.
• Solubility: Soluble in water and oils, making it versatile for different formulations.
• pH: Generally neutral to slightly acidic, around 6-7.
• Odor: Mild, characteristic of ester compounds.
• Stability: Stable under normal storage conditions but should be protected from extreme temperatures.

Production Process

• Esterification: PEG-4 Laurate is produced through the esterification process, where lauric acid is reacted with PEG-4 in the presence of a catalyst.
• Purification: The resulting compound is purified to remove any unreacted materials and by-products.
• Formulation: The purified PEG-4 Laurate is incorporated into cosmetic products, often combined with other emulsifying agents for enhanced performance.

Applications

• Medical: Limited use in specific formulations requiring emulsification.
• Cosmetics: Commonly included in creams, lotions, and hair care products for its emulsifying and skin-conditioning effects.

INCI Functions:

Surfactant - Emulsifying agent. Emulsions are thermodynamically unstable and are used to soothe or soften the skin and emulsify, so they need a specific, stabilising ingredient. This ingredient forms a film, lowers the surface tension and makes two immiscible liquids miscible. A very important factor affecting the stability of the emulsion is the amount of the emulsifying agent. Emulsifiers have the property of reducing the oil/water or water/oil interfacial tension, improving the stability of the emulsion and also directly influencing the stability, sensory properties and surface tension of sunscreens by modulating the filmometric performance.

Surfactant - Cleansing agent. Cosmetic products used to cleanse the skin utilise the surface-active action that produces a lowering of the surface tension of the stratum corneum, facilitating the removal of dirt and impurities. 

CAS   9004-81-3

• Industrial Uses: Occasionally utilized in formulations requiring emulsification and moisture retention.

Environmental and Safety Considerations

Responsible sourcing and production practices are essential to ensure that the ingredient is free from harmful contaminants and produced sustainably. 

Cosmetic Safety

PEG (Polyethylene glycol) polymerize condensed ethylene oxide and water and are referred to as polyethylene glycols, but they are actually complex chemical components, polymers bonded together. For example, plastic is polyethylene and has a hard consistency, while polyethylene aggregated with glycol forms a liquid. PEGylation is produced not only as heterification but also as transesterification, which is the transformation of an alcohol by an ester. 

The number that appears after the abbreviation PEG represents the molecular weight, and the higher this number is, the less it penetrates the skin.

The term 'eth' refers to the ethoxylation reaction with ethylene oxide after which residues of ethylene oxide and 1,4-dioxane, chemical compounds considered carcinogenic, may remain. The degree of safety therefore depends on the degree of purity of the compound obtained. No manufacturer appears to provide this information on the label, at least as of the date of this review.

Kim MC, Park SY, Kwon SY, Kim YK, Kim YI, Seo YS, Cho SM, Shin EC, Mok JH, Lee YB. Application of Static Headspace GC-MS Method for Selective 1,4-Dioxane Detection in Food Additives. Foods. 2023 Sep 2;12(17):3299. doi: 10.3390/foods12173299. 

Abstract. "Efficient detection methods must be developed for 1,4-dioxane due to its suspected status as a human carcinogen, which is highly mobile in food and environmental resources. In this regard, this experiment has been conducted to develop reliable and selective detection and measurement methods by using static headspace (SH) isolation, followed by gas chromatography-mass spectrometry (GC-MS). A new method was developed for determining the spiked 1,4-dioxane contents in a polyethylene glycol 600 (PEG 600). The optimal condition for SH-GC-MS was discussed. The representative ions of 1,4-dioxane and 1,4-dioxane-d8 in the SIM mode of MS are 88 and 96, respectively, and the peaks of the SIM mode were separated and confirmed. The linear range for the method covers 0.25 to 100 mg/L with a coefficient of determination (R2) ≥ 0.999. The method applicability was demonstrated by spike recovery across a variety of food additives (i.e., chlorine bitartrate, choline chloride, polysorbate 20 and 60, and PEG 1000). All spike recovery from the tested samples was in the range of 89.50-102.68% with a precision of 0.44-11.22%. These findings suggest a new analytical method for food safety inspection, and could be applicable for ensuring the safety of foods and environmental and public health on a broad scale."