glycols

Glycols are a subset of diols, organic compounds that contain two hydroxyl groups. They are typically colorless liquids at room temperature and are highly soluble in water. The most widely produced and used glycols are ethylene glycol and propylene glycol, but numerous other glycols such as diethylene glycol, triethylene glycol, dipropylene glycol, and higher oligomers are also manufactured and sold for specialized applications.

Ethylene glycol (ethane-1,2-diol) is a clear, sweet-tasting liquid used mainly as an antifreeze formulation and as a feedstock for polyester resins and polyurethanes. Propylene glycol (propylene-1,2-diol) is similarly a clear, nearly odorless liquid that is less toxic and widely used as a food additive, humectant, cosmetic vehicle, and pharmaceutical excipient, as well as a heat-transfer fluid and antifreeze in some engines.

Most glycols are produced by the catalytic hydration or hydroxyethylation of epoxides derived from ethylene or propylene oxide, themselves produced from ethylene and propylene, typically via petrochemical routes. In industry, glycols serve as solvents, plasticizers, and monomer precursors for polymers such as PET and polyurethanes.

Safety and environmental considerations: Ethylene glycol is highly toxic if ingested, causing metabolic acidosis and kidney failure; propylene glycol has lower acute toxicity but can cause adverse effects at high doses. Handling requires proper ventilation and personal protective equipment. Glycols are generally biodegradable, but spills can pose aquatic toxicity; disposal should follow local regulations and industry guidelines.