
Propylene glycol is a chemical that is produced by reaction of propylene oxide with water. It is a colorless, clear, almost odorless, viscous liquid which has a faint sweet taste. Propylene glycol is miscible with water, chloroform, and acetone and is hygroscopic in nature. It is chemically neutral that does not react with other substances. This property of propylene glycol makes it useful in mixing contrasting elements such as perfumes. Unique features of propylene glycol makes it useful in a wide variety of applications. It is used as solvent, holds and dissolves active ingredients equally in the medium, acts as an emulsifier and excipient, reduced freezing point and many more. Propylene glycol is manufactured in two grades namely, industrial or technical grade and USD/EP grade. It designates the requirements for the U.S. and European Pharmacopeia, but it has use in the personal care, food and feed applications. Dipropylene glycol is used in unsaturated polyester resins and personal care products and tripropylene glycol has application in acrylates and polyurethanes.