Propylene glycol (IUPAC name: propane-1,2-diol) is a viscous, colorless liquid, which is nearly odorless but possesses a faintly sweet taste. Its chemical formula is CH3CH(OH)CH2OH. Containing two alcohol groups, it is classed as a diol. It is miscible with a broad range of solvents, including water, acetone, and chloroform. In general, glycols are non-irritating and have very low volatility.[4]
It is produced on a large scale primarily for the production of polymers. In the European Union, it has E-number E1520 for food applications. For cosmetics and pharmacology, the number is E490. Propylene glycol is also present in propylene glycol alginate, which is known as E405. Propylene glycol is a compound which is GRAS (generally recognized as safe) by the US Food and Drug Administration under 21 CFR x184.1666, and is also approved by the FDA for certain uses as an indirect food additive. Propylene glycol is approved and used as a vehicle for topical, oral, and some intravenous pharmaceutical preparations in the U.S. and in Europe.
| Names | |
|---|---|
| Preferred IUPAC name Propane-1,2-diol | |
| Other names Propylene glycol α-Propylene glycol 1,2-Propanediol 1,2-Dihydroxypropane Methyl ethyl glycol Methylethylene glycol |
| Related compounds | |
|---|---|
Related glycols | Ethylene glycol, 1,3-propanediol |
Propylene glycol is also used in various edible items such as coffee-based drinks, liquid sweeteners, ice cream, whipped dairy products and soda.[9][10] Vaporizers used for delivery of pharmaceuticals or personal-care products often include propylene glycol among the ingredients.[4] In alcohol-based hand sanitizers, it is used as a humectant to prevent the skin from drying.[11] Propylene glycol is used as a solvent in many pharmaceuticals, including oral, injectable, and topical formulations. Many pharmaceutical drugs which are insoluble in water utilize propylene glycol as a solvent and carrier; benzodiazepine tablets are one example.[12]Propylene glycol is also used as a solvent and carrier for many pharmaceutical capsule preparations. Additionally, certain formulations of artificial tears use propylene glycol as an ingredient.[13]
The freezing point of water is depressed when mixed with propylene glycol. It is used as aircraft de-icing fluid.[4][14] Water-propylene glycol mixtures dyed pink to indicate the mixture is relatively nontoxic are sold under the name of RV or marine antifreeze. Propylene glycol is frequently used as a substitute for ethylene glycol in low toxicity, environmentally friendly automotive antifreeze. It is also used to winterize the plumbing systems in vacant structures.[15] The eutectic composition/temperature is 60:40 propylene glycol:water/-60 °C.[16][17] The −50 °F/−45 °C commercial product is, however, water rich; a typical formulation is 40:60.[18]
Along with vegetable glycerin as the main ingredient (<1–92%) in e-liquid used in electronic cigarettes, where it is aerosolized to resemble smoke. It serves as both the carrier for substances like nicotine and cannabinoids, as well as for creating a vapor which resembles smoke.[19]
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Propylene glycol is expected to degrade rapidly in water from biological processes, but is not expected to be significantly influenced by hydrolysis, oxidation, volatilization, bioconcentration, or adsorption to sediment.[70] Propylene glycol is readily biodegradable under aerobic conditions in freshwater, in seawater and in soil. Therefore, propylene glycol is considered as not persistent in the environment.
https://en.wikipedia.org/wiki/Propylene_glycol
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