propyleenglycol

Propylene glycol, or propane-1,2-diol (C3H8O2), is a synthetic organic compound widely used as a solvent, humectant, and vehicle in food, pharmaceuticals, cosmetics, and industrial applications.

It is a colorless, nearly odorless, viscous liquid that is hygroscopic and miscible with water and many organic solvents. Its boiling point is about 188°C and its melting point is -59°C; density is around 1.04 g/cm3 at 20°C.

Production primarily involves the catalytic hydration of propylene oxide to give propylene glycol, followed by purification. Alternative routes include hydrogenation of glycerol. The processes aim to minimize diol impurities and residual catalysts to meet product specifications for various end-uses.

In food, cosmetics, and pharmaceuticals, propylene glycol serves as a humectant, solvent, and carrier for flavors and active ingredients; in the chemical industry, it is used as an antifreeze, heat-transfer fluid, and plasticizer. It is also employed as a solvent in inks, coatings, and personal care products, and as a vehicle for certain injectable and oral medicines.

Safety and regulation: Propylene glycol is generally regarded as having relatively low acute toxicity and is widely approved for use in foods (as a GRAS substance) and pharmaceuticals. It can cause skin or eye irritation in concentrated forms and may cause central nervous system effects or metabolic disturbances at very high oral doses. It is readily biodegradable and typically presents low environmental risk at conventional-use concentrations.