Propylene glycol, or propane-1,2-diol in IUPAC nomenclature, is an organic double alcohol. It has a chemical formula of C3H8O2 and a CAS number of 57-55-6. It is a thick, clear, and nearly odorless substance with a faintly sweet taste. Propylene glycol is similar in characteristics with glycerin - hygroscopic, soluble with water, acetone, and chloroform.
Manufacture
Propylene glycol is usually sourced from propylene oxide. Production is more or less similar with glycerin, using either catalytic (150°-180°C) or non-catalytic high-temperature process (200°-220°C). the process is manufactured using ion exchange resin or a small amount of sulfuric acid or alkali. Final products include 20% propylene glycol, 1.5% dipropylene glycol, and other polypropylene glycols. Glycerol can be converted from propylene glycol as well.
Usage
Propylene glycol serves as humectant and preservative for various food products. It is mixed in snacks, pastries, soda drinks, and ice cream. It serves as cooling agent for alcoholic beverages and further extends freezing time for food. Likewise, propylene glycol is used as a solvent for different medical preparations like oral, injectable, and topical formulations. As a humectant, it is labeled as E1520. Sunscreens, shampoos, make-ups, creams, deodorants, and other toiletry items contain this versatile alcohol as well. Its hygroscopic property makes it a suitable moisturizer for toothpaste, mouth wash, and cigarettes. Propylene glycol serves as a carrier for perfume oils and soap bases.
Industrially, propylene glycol is used as antifreeze for water systems and heaters because it is less toxic. Moreover, it is added to other household items like furniture polish and glass cleaners. Photographic chemicals use propylene glycol as a solvent.
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