Propylene glycol (chemical formula: C₃H₈O₂) is a synthetic organic compound that is colorless, odorless, and tasteless. It is a type of alcohol, specifically a diol (a compound containing two hydroxyl groups, -OH), and is commonly used in a variety of applications, particularly in food, pharmaceuticals, and industrial products.
It is closely related to ethylene glycol, but is considered safer for human consumption and general use, which is why it’s preferred in many consumer products.
Properties:
- Molecular Formula: C₃H₈O₂
- IUPAC Name: Propane-1,2-diol
- Molar Mass: 76.09 g/mol
- Boiling Point: 188.2°C (370.8°F)
- Melting Point: −59°C (−74.2°F)
- Density: 1.036 g/cm³ at 20°C
Key Uses of Propylene Glycol:
Paints and Coatings
Solvent: PG is used in paints, varnishes, and coatings as a solvent to help disperse pigments and other ingredients, aiding in the smooth application and drying of the product.
Chemical Intermediate in Manufacturing
Production of other chemicals: PG is used as a precursor or intermediate in the production of other chemicals such as propylene glycol ethers, propylene carbonate, and plasticizers.
Food Industry
Propylene Glycol (PG) is commonly used as a humectant (moisture-retaining agent), solvent, and preservative in food products. It’s used in:
- Salad dressings, processed foods, and baked goods.
- Food coloring and flavoring, ensuring they dissolve properly.
- Ice cream, as it prevents the formation of ice crystals and helps maintain texture.
Pharmaceuticals
PG is used as a carrier for active ingredients in pharmaceuticals, helping to dissolve and deliver the medicine effectively. It is found in:
- Oral medications, cough syrups, elixirs, and oral suspensions.
- As a stabilizer in injectable drugs and topical ointments.
Cosmetics and Personal Care
PG is used extensively in moisturizers, shampoos, lotions, and other personal care products. It:
- Acts as a humectant, retaining moisture and enhancing product stability.
- Is found in deodorants, skin care products, and hair care items.
Vaping Products
Propylene glycol is a common ingredient in e-liquids for vaping. It is used to:
- Produce the vapor when heated and to carry flavorings.
Antifreeze and Coolants
Propylene glycol is used as an alternative to ethylene glycol in some automotive and industrial antifreeze products, especially in:
- Applications where non-toxic properties are desired, such as in food processing facilities.
- Situations where accidental spills might occur in animal areas.
Industrial Applications
PG is used in various industrial applications, including:
- Hydraulic fluids, brake fluids, and de-icing solutions for airplanes and runways.
- Air conditioning systems as a heat transfer fluid.