What is Polyethylene glycol

Polyethylene glycol is a high molecular polymer with the chemical formula HO(CH2CH2O)nH. It is non-irritating, slightly bitter in taste, has good water solubility, and has good compatibility with many organic components. It has excellent lubricity, moisture retention, dispersibility, adhesive, can be used as antistatic agent and softener, etc., in cosmetics, pharmaceuticals, chemical fiber, rubber, plastics, paper, paint, electroplating, pesticides, metal processing and food It is widely used in processing and other industries.

Chemical structure

HO(CH2CH2O)nH is formed by the gradual addition polymerization of ethylene oxide and water or ethylene glycol.

Chemical traits

The properties vary according to the relative molecular mass, ranging from colorless and odorless viscous liquid to waxy solid. Those with a molecular weight of 200-600 are liquid at room temperature, and those with a molecular weight of 600 or more will gradually become semi-solid. The properties vary with the average molecular weight. From colorless and odorless viscous liquid to waxy solid. As the molecular weight increases, its moisture absorption capacity decreases accordingly. This product is soluble in water, ethanol and many other organic solvents. Low vapor pressure, stable to heat, acid and alkali. Does not work with many chemicals. It has good hygroscopicity, lubricity and cohesiveness. Non-toxic and non-irritating. The average molecular weight is 300, n=5～5.75, the melting point is -15～8℃, and the relative density is 1.124～1.130. The average molecular weight is 600, n=12-13, the melting point is 20-25℃, the flash point is 246℃, and the relative density is 1.13 (20℃). The average molecular weight is 4000, n=70-85, and the melting point is 53-56°C.

Under normal conditions, polyethylene glycol is very stable, but it can interact with oxygen in the air at a temperature of 120°C or higher. In an inert atmosphere (such as nitrogen and carbon dioxide), it will not change even if it is heated to 200-240°C, and thermal cracking will occur when the temperature rises to 300°C. Adding antioxidants, such as phenothiazine with a mass fraction of 0.25% to 0.5%, can improve its chemical stability. Any of its decomposition products are volatile and will not produce hard shells or slimy deposits.

Polyethylene glycol is a polymer of ethylene oxide hydrolysate. It is non-toxic and non-irritating and is widely used in various pharmaceutical preparations. Low-molecular-weight polyethylene glycols are relatively more toxic. Taken together, glycols have relatively low toxicity. Topical application of polyethylene glycol, especially mucosal administration, can cause irritation and pain. In the topical lotion, this product can increase the flexibility of the skin and has a moisturizing effect similar to that of glycerin. Diarrhea can occur in large doses orally. In injections, the maximum concentration of polyethylene glycol 300 is about 30% (V/V), and hemolysis may occur if the concentration is greater than 40% (V/V).

Polyethylene oxide and water addition polymer. Those with a molecular weight below 700 are colorless, odorless, non-volatile viscous liquids at 20°C, slightly water-absorbent. Those with a molecular weight between 700 and 900 are semi-solid. Those with a molecular weight of 1000 and above are light white waxy solids, flake paraffins, or fluid powders. It is miscible in water, soluble in many organic solvents, such as alcohols, ketones, chloroform, glycerides and aromatic hydrocarbons, etc.; insoluble in most aliphatic hydrocarbons and ether.

As the molecular weight increases, the water solubility, vapor pressure, water absorption, and solubility of organic solvents decrease, while the freezing point, relative density, flash point and viscosity increase accordingly. It is thermally stable, does not work with many chemicals, and does not hydrolyze.

Compatibility

Polyethylene glycol is a non-ionic water-soluble polymer. It can be compatible with many more polar substances, and has poor compatibility with low polar substances. Polyethylene glycol with low molecular weight has better compatibility. Polyethylene glycol can be compatible or partially compatible with protein, oxidized starch, nitrocellulose, polyvinyl acetate and zein. It is immiscible with beeswax, castor oil, gelatin, gum arabic, mineral oil, olive oil and paraffin wax.

Compatibility taboo

Liquid and solid grades of polyethylene glycol are not compatible with certain pigments;

Can reduce the activity of antibiotics, especially penicillin and bacitracin;

Preservatives of hydroxyphenyl esters can weaken the antiseptic effect due to the complexation of polyethylene glycol;

Phenol, tannic acid and salicylic acid can soften and liquefy;

Sulfonamides and anthranol can change color with their effects;

Compatible with sorbitol can produce precipitation.

The main purpose

Polyethylene glycol and polyethylene glycol fatty acid esters are widely used in the cosmetics industry and the pharmaceutical industry. Because polyethylene glycol has many excellent properties: water solubility, non-volatility, physiological inertness, mildness, lubricity, and makes the skin moist, soft, and pleasant after use. Different molecular weight fractions of polyethylene glycol can be selected to change the viscosity, hygroscopicity and tissue structure of the product. Polyethylene glycol with low molecular weight (Mr<2000) is suitable for use as a wetting agent and consistency regulator, used in creams, lotions, toothpaste and shaving cream, etc., and also suitable for non-washed hair care products. Gives hair a silky luster. Polyethylene glycol with high molecular weight (Mr>2000) is suitable for lipsticks, deodorant sticks, soaps, shaving soaps, foundations and cosmetics. In cleaning agents, polyethylene glycol is also used as a suspending agent and thickening agent. In the pharmaceutical industry, it is used as a base for ointments, emulsions, ointments, lotions and suppositories.

Polyethylene glycol is widely used in a variety of pharmaceutical preparations, such as injections, topical preparations, and ophthalmic preparations, oral and rectal preparations. Solid-grade polyethylene glycol can be added to liquid polyethylene glycol to adjust the viscosity for topical ointment; polyethylene glycol mixture can be used as a suppository base; polyethylene glycol aqueous solution can be used as a suspending agent or used to adjust other The viscosity of the suspension medium; polyethylene glycol is used in combination with other emulsifiers to increase the stability of the emulsion. In addition, polyethylene glycol is also used as a film coating agent, tablet lubricant, controlled release material and so on.

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