Industrial-grade 99% PEG Polyethylene Glycol CAS 25322-68-3

What is Poly(ethylene glycol)? How does it work?

Poly(ethylene glycol), also known as polyethylene glycol, polyoxyethylene, PEG, PEO, POE, or macrogol, is a polyether polymer obtained by ring-opening polymerization of ethylene oxide. Its general chemical formula is H−(O−CH2−CH2)n−OH, CAS number 25322-68-3, and E number E1521. It is a series of products with molecular weights ranging from hundreds to millions: low molecular weight products are colorless, viscous liquids, while high molecular weight products are white, waxy solids. It is soluble in water, methanol, ethanol, acetonitrile, benzene, and dichloromethane, but insoluble in diethyl ether and hexane. Its aqueous solutions are neutral and hygroscopic. With its excellent water solubility, adjustable molecular weight, terminal hydroxyl reactivity, flexible chain lubrication and low toxicity, industrial-grade polyethylene glycol is widely used as a raw material for surfactants and emulsifiers, polyurethane polyols, metalworking fluids, plastic and rubber processing aids, coating and ink additives, textile and papermaking aids, ceramic binders, battery electrolytes, reaction media, agricultural formulation additives and cultural relic protection materials.

Basic identification information : Chemical formula C2nH4n+2On+1 (structural formula H−(O−CH2−CH2)n−OH); CAS No. 25322-68-3; EINECS 500-038-2; UNII 3WJQ0SDW1A; ECHA 100.105.546; ChEMBL 1201478; E No. E1521; Aliases: polyethylene glycol, polyoxyethylene, polyethylene oxide, PEG, PEO, POE, macrogol, Carbowax, etc.

Structurally , polyethylene glycol is composed of repeating ethylene oxide units (−O−CH2−CH2−) linked by ether bonds, with a hydroxyl group at each end; the molecular chain has a flexible helical conformation, and the oxygen in the ether bonds can form hydrogen bonds with water.

Physically , polyethylene glycol (PEG) is a colorless to white liquid, paste, or waxy solid. Its state transitions from liquid to solid as its molecular weight increases: PEG 200-600 is a viscous liquid, PEG 1000-2000 is a paste, and PEG 4000 and above are waxy solids. Its melting point increases with molecular weight (PEG 4000 approximately 50-58℃, PEG 6000 approximately 55-63℃). Its density is approximately 1.125 g/cm³. It is soluble in water, methanol, ethanol, acetonitrile, benzene, and dichloromethane, but insoluble in diethyl ether and hexane. It is hygroscopic. Its flash point is 182-287℃. It has good thermal stability, but prolonged exposure to high temperatures or contact with oxidants may lead to oxidative degradation.

Chemically , polyethylene glycol is a hydroxyl-terminated polyether: the primary hydroxyl groups at both ends can undergo esterification, etherification, and urethane esterification reactions; it reacts with isocyanates to form polyurethanes, esterifies with fatty acids to form PEG ester surfactants, and continues to extend its chain with ethylene oxide, etc.; the ether bond is chemically stable, resistant to acids and alkalis (the ether bond can break under long-term action of strong acids and alkalis), and has moderate oxidation resistance; the molecular chain has good flexibility and can be used as a plasticizer and lubricant; the terminal hydroxyl groups endow it with reactivity, making it the parent material for the synthesis of many derivatives.

Why does polyethylene glycol play these roles in various industrial fields? Its mechanisms of action mainly include the following:

Hydrophilic and water-soluble mechanism : The ether oxygen (−O−) in the main chain of polyethylene glycol can form hydrogen bonds with water molecules, making it a water-soluble polymer. The larger the molecular weight, the greater the change in water solubility window and hygroscopicity. This is the basis for its use as a water-soluble lubricant, an additive in water-based systems, and a hydrophilic segment.

The mechanism of adjustable molecular weight : The degree of polymerization determines the chain length, which in turn determines the physical state (liquid, paste, wax), viscosity, melting point and water solubility. Different molecular weights correspond to different application windows, allowing the appropriate specifications to be selected according to the application. This is the premise for its serialized application.

Hydroxyl-terminated reactive mechanism : The primary hydroxyl groups at both ends can react with fatty acids, fatty alcohols, alkylphenols, isocyanates, etc., to attach polyethylene glycol segments to ester, ether and polyurethane structures, forming surfactants, polyether polyols and other derivatives. This is the chemical basis for its use as a synthetic parent.

Flexible chain lubrication film formation mechanism : Polyethylene glycol molecular chains are flexible and can be adsorbed and spread to form films on the surfaces of metals, fibers, paper and other materials, reducing the coefficient of friction and providing boundary lubrication. This is the basis for its use as a metalworking fluid, textile and papermaking auxiliary agent and release agent.

Plasticizing mechanism : Polyethylene glycol with a suitable molecular weight can penetrate into the polymer chains, weakening the inter-chain forces, increasing the chain segment mobility, and reducing the hardness and brittleness of the plastic. This is the basis for its use as a plasticizer for plastics such as PVC.

Amphiphilic coupling mechanism : The polyethylene glycol segments are hydrophilic ends, which, after coupling with hydrophobic groups, form an amphiphilic structure. They can be oriented at the oil-water interface, reduce interfacial tension, and achieve emulsification, dispersion and solubilization. This is the basis for its use as a hydrophilic head group of surfactants.

Electrolyte complexation mechanism : The ether bond oxygen on the polyoxyethylene chain segment can coordinate and complex with metal cations such as lithium ions to form ion transport channels, making polyoxyethylene an ion conductor. This is the basis for its use as a solid polymer electrolyte.

Bioinertness and low toxicity mechanism : Polyethylene glycol is chemically stable and not easily metabolized and degraded by organisms. Its single oral toxicity is very low, making it safe for use in daily chemical raw materials and other human contact scenarios.

II. All Uses of Industrial Grade Poly (ethylene glycol)

1. Surfactant and Emulsifier Raw Materials (Surfactant Industry)

Corresponding products: fatty alcohol polyoxyethylene ether (AEO), alkylphenol polyoxyethylene ether (OP-10), Tween (polysorbate), Span, narrow distribution ethoxylates, polyether nonionic surfactants ( laundry detergent, dishwashing liquid, shampoo, etc. ) , pesticide emulsifiers, emulsion polymerization emulsifiers, etc.

Why it can be used for this purpose: Polyethylene glycol segments are the hydrophilic parts of surfactant molecules. Through ethoxylation, they couple with hydrophobic groups such as fatty alcohols, alkylphenols, and fatty acids to form an amphiphilic structure. They are oriented at the oil-water interface, reducing interfacial tension and achieving emulsification, dispersion, and solubilization. It is the core raw material for manufacturing nonionic surfactants.

2. Polyurethane polyols and elastomer raw materials (polyurethane industry)

Corresponding products: polyether polyols, spandex elastic fibers, polyurethane flexible foam, polyurethane rigid foam, polyurethane elastomers, PU synthetic leather, polyurethane coating resins, etc.

Why it can be used for this purpose: The terminal hydroxyl groups of polyethylene glycol react with isocyanate to produce polyurethane. Its flexible polyether segments, as soft segments, give polyurethane elasticity and flexibility. It is a key component of polyether polyols in spandex elastic fibers, foam plastics and elastomer formulations.

3. Metalworking fluids and industrial lubricants (metalworking industry)

Corresponding products: water-soluble cutting fluid, grinding fluid, wire drawing fluid, rolling fluid, quenching media, metal cleaning agents, water-soluble rust inhibitors and lubricants, etc.

Why it can be used in this application: Polyethylene glycol has good water solubility and flexible molecular chains, which can be adsorbed on metal surfaces to form films, reducing friction and wear. At the same time, it is easily soluble in water and easy to clean, and has cooling, lubrication and cleaning functions. It is an important component of water-based metalworking fluids and industrial lubricants.

4. Plastics and Rubber Processing Aids (Plastics/Rubber Industry)

Corresponding products: PVC plasticizers, plastic release agents, internal lubricants, antistatic agents, rubber processing aids, color masterbatch carriers, etc.

Why it can be used for this purpose: Polyethylene glycol with a suitable molecular weight can penetrate into the polymer chains to weaken the inter-chain forces, reduce the hardness and brittleness of plastics, and play a plasticizing role; its flexible chains form a film at the interface between the mold and the product, which facilitates demolding, and has internal lubrication and antistatic functions, making it a general-purpose additive for plastic and rubber processing.

5. Coatings, inks, and printing consumables additives (coating/ink industry)

Corresponding products: inkjet ink solvents, printhead lubricants, water-based coating leveling agents, ink dispersants, paint fillers, paper coating agents, etc.

Why it can be used for this purpose: Polyethylene glycol has good solubility and compatibility with dyes and pigments. It can adjust the viscosity and jetting performance of ink and lubricate the printhead. In water-based coatings, it acts as a leveling and dispersing agent to improve the uniformity of the coating film. It is a commonly used additive in the formulation of coatings, inks and printing consumables.

6. Textile printing and dyeing auxiliaries (textile industry)

Corresponding products: softeners, antistatic agents, leveling agents, penetrants, warp sizing agents, chemical fiber oils, etc.

Why it can be used in this way: Polyethylene glycol adsorbs onto the fiber surface to form a hydrophilic lubricating film, giving the fabric a soft feel and reducing static electricity accumulation. Its derivatives improve leveling and penetration in the dye bath and are commonly used auxiliary components in textile printing and dyeing processes.

7. Papermaking additives (papermaking industry)

Corresponding products: coating lubricants, paper softeners, calendering aids, anti-blocking agents, wet end additives, etc.

Why it can be used for this purpose: Polyethylene glycol acts as a lubricant in paper coating formulations, which can reduce friction between the doctor blade and the coating, improve the gloss and smoothness of the coating, and give the paper softness and non-stick properties. It is a commonly used additive in paper coating and paper processing.

8. Ceramic binders and powder metallurgy additives (ceramics/metallurgical industry)

Corresponding products: technical ceramic binders, alumina/silicon carbide molding binders, ceramic granulation agents, powder metallurgy binders, electronic ceramic additives, etc.

Why it can be used for this purpose: Polyethylene glycol aqueous solution has adhesive properties and can be used as a molding binder for ceramic powder and metal powder. It allows the powder to maintain the strength of the green body before pressing and sintering, and completely burns off the ash during the sintering process, leaving no ash. It is a commonly used organic binder for technical ceramics and powder metallurgy molding.

9. Cultural Relics Conservation and Wood Stabilizers (Cultural Relics Conservation/Wood Industry)

Corresponding products: water-immersed wood preservative, archaeological artifact reinforcement agent, green wood stabilizer, desalination aid for wooden artifacts, etc.

Why it can be used for this purpose: Polyethylene glycol can penetrate into the interior of cultural relics such as wood to replace moisture. After drying, it maintains dimensional stability and prevents cracking and deformation. It is used for the protection and restoration of shipwrecks and water-damaged wooden cultural relics, as well as for the stabilization of raw materials. It is a classic material in the field of cultural relic protection.

Summarize

Polyethylene glycol (CAS 25322-68-3) is a polyether polymer formed by the ring-opening polymerization of ethylene oxide. Its core properties include water solubility, adjustable molecular weight, reactive terminal hydroxyl groups, flexible chain lubrication, and low toxicity. Industrially, it is widely used as a raw material for surfactants and emulsifiers, polyurethane polyols, metalworking fluids, plastics and rubber processing aids, coatings and inks, textiles and papermaking, ceramic binders, and cultural relic preservation materials. Understanding its polyether structure and the activity of its terminal hydroxyl groups explains why it can function as a hydrophilic segment of nonionic surfactants, a soft segment of polyurethane polyols, and also provide lubrication, plasticizing, bonding, ion conduction, and cultural relic preservation—this is precisely why it spans the fields of surfactants, polyurethanes, metalworking, plastics, coatings and inks, textiles, papermaking, ceramics, and cultural relic preservation.