PEG (Polyethylene Glycol) is a non-ionic polymer made from the polymerization of ethylene oxide. It is widely used in various industries, including cosmetics, pharmaceuticals, food, and industrial applications, due to its properties as a surfactant, emulsifier, solubilizer, humectant, and lubricant.
Chemical Composition and Structure
PEG consists of repeating units of ethylene oxide (C₂H₄O) that form long chains. These chains are connected by oxygen atoms and hydroxyl groups (-OH), which give the polymer its hydrophilic (water-attracting) properties.
The general chemical structure of polyethylene glycol is represented as:
The length of the polymer chain (the value of n) can vary, affecting the properties of the PEG, such as solubility in water, viscosity, and consistency. PEG with shorter chains is typically liquid, while longer chains form solid or wax-like substances.
Physical Properties
Appearance: PEG typically appears as a colorless and odorless liquid (for lower molecular weights) or a white waxy solid (for higher molecular weights).
Solubility: It is soluble in water and many organic solvents, such as alcohol and propylene glycol, which allows it to be used in both aqueous and alcoholic formulations.
Viscosity: The viscosity of PEG increases with the length of the polymer chain, meaning lower molecular weight versions are more fluid, while higher molecular weight versions are thicker and solidified.
Stability: PEG is generally stable at room temperature and under normal storage conditions. It is resistant to degradation and crystallization.
Benefits and Functions
Surfactant and Emulsifier: PEG is commonly used as a surfactant and emulsifier in cosmetics and personal care products, helping to combine water and oil ingredients.
Solubilizer: It is used to solubilize hydrophobic ingredients, such as oils and fragrances, in aqueous solutions, making it easier to incorporate these ingredients into water-based formulations.
Humectant: PEG acts as a humectant, retaining moisture and improving skin hydration.
Lubricant: It is used as a lubricant in pharmaceutical, cosmetic, and industrial products, improving texture and feel.
Carrier for Active Ingredients: PEG is used as a carrier to help deliver active ingredients in cosmetic and pharmaceutical products, enhancing absorption and effectiveness.
Applications
Cosmetics and Personal Care
Moisturizers: PEG is commonly used in lotions, creams, and serums to improve texture, stability, and hydration.
Shampoos and Conditioners: It is used in hair care products to improve the mixing of water and oils, enhancing texture and foaming properties.
Facial Cleansers and Toners: PEG functions as a solubilizer for oils and helps remove dirt and impurities.
Deodorants: PEG is used as an emulsifier in deodorant formulations for better product distribution on the skin.
CAS: 25322-68-3
Pharmaceuticals
Creams and Ointments: PEG is included in formulations to improve the delivery of active ingredients and improve product consistency.
Oral Medications: It is used in tablet formulations as a binder and solubilizer to ensure proper absorption of active compounds.
Ophthalmic Lubricants: PEG is used in eye drops for improving moisture and lubrication of dry eyes.
Industrial Applications
Environmental and Safety Considerations
Biodegradability: PEG is generally considered biodegradable, but the biodegradability rate may vary depending on the length of the polymer chains.
Safety: PEG is generally considered safe for use in cosmetics and pharmaceuticals, but it may cause irritation or allergic reactions in sensitive individuals. It is recommended to conduct a patch test before using products containing this ingredient, especially for people with highly sensitive skin.
Sustainability: Since PEG is derived from petrochemical sources, there are environmental concerns regarding its sustainability. However, some variants are produced from renewable sources, such as propylene glycol.
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."
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