What Is Propylene Glycol?

Propylene Glycol, also known as 1,2-Propanediol, is a clear, colorless, viscous liquid with the chemical formula C₃H₈O₂ and CAS No. 57-55-6. It is a dihydric alcohol with two hydroxyl groups, giving it good water miscibility and solvent properties.

Propylene Glycol has a molecular weight of approximately 76.09 g/mol and a boiling point of about 187°C. It has a low melting point of approximately -60°C and a density of around 1.04 g/cm³, depending on the measurement temperature.

Because of its combination of low volatility, hygroscopicity, solvent capability and broad compatibility with other substances, Propylene Glycol is widely used in industrial and consumer applications.

Physical and Chemical Properties

Propylene Glycol is a colorless, nearly odorless and hygroscopic liquid. It is miscible with water and many common organic solvents, making it useful as a solvent and carrier in a wide range of formulations.

Basic properties of Propylene Glycol:

• Chemical Name: Propylene Glycol
• CAS No.: 57-55-6
• Chemical Formula: C₃H₈O₂
• Molecular Weight: 76.09 g/mol
• Appearance: Colorless, viscous liquid
• Boiling Point: Approximately 187°C
• Melting Point: Approximately -60°C
• Density: Approximately 1.036–1.04 g/cm³
• Solubility: Miscible with water and many organic solvents

These properties make Propylene Glycol suitable for applications requiring an effective solvent, humectant, heat-transfer medium or formulation ingredient.

Main Applications of Propylene Glycol

Solvent and Formulation Ingredient

Propylene Glycol is widely used as a solvent for various organic substances. Its ability to dissolve or carry different ingredients makes it useful in formulations for coatings, inks, cleaners, fragrances and other chemical products.

It can also be used as a carrier or co-solvent where controlled evaporation and good compatibility with water are required.

Paints, Coatings and Resins

In the coatings and chemical industries, Propylene Glycol can function as a solvent, coalescing aid or formulation component. Its compatibility with water and organic materials makes it useful in certain water-based coatings, paints, resins and surface-treatment formulations.

It is also used in the production and formulation of polyester-related materials and other chemical products.

Pharmaceutical and Personal Care Products

Propylene Glycol is widely used in pharmaceutical formulations as a solvent and excipient. It can help dissolve active ingredients and improve the stability or uniformity of formulations.

It is also used in cosmetics and personal care products, including creams, lotions and other formulations where its solvent and moisture-retaining properties are beneficial.

Food and Flavor Applications

Certain grades of Propylene Glycol are used in food-related applications as a solvent, humectant and carrier for flavors and other ingredients. Food-grade Propylene Glycol is manufactured and controlled according to the applicable requirements for its intended use.

Antifreeze and Heat Transfer Fluids

Propylene Glycol is also used as a component of antifreeze and heat-transfer formulations. Its relatively low freezing point and favorable physical properties make it suitable for applications where reduced toxicity compared with some alternative glycols is desirable.

It can be found in refrigeration, cooling and deicing-related applications as well as other heat-transfer systems.

Propylene Glycol Grades

Different grades of Propylene Glycol are available for different end uses. Industrial grade, USP/EP or pharmaceutical grade, and food-grade Propylene Glycol may have different specifications and purity requirements.

For industrial applications, customers should select the appropriate grade according to the intended use and required specifications. For pharmaceutical or food applications, relevant regulatory and quality requirements should be confirmed before purchase.

Packaging and Storage

Propylene Glycol should be stored in tightly closed containers in a cool, dry and well-ventilated area. Suitable packaging may include drums, IBC tanks and bulk containers, depending on the customer's required quantity and transportation conditions.

Before shipment, buyers should confirm the required grade, purity, packaging, loading quantity and applicable documentation, such as COA and SDS.

Conclusion

Propylene Glycol (CAS No. 57-55-6) is a versatile diol with excellent water miscibility, solvent properties and broad application potential. It is widely used in coatings, resins, pharmaceuticals, cosmetics, food-related formulations, antifreeze and heat-transfer fluids.

Its combination of chemical compatibility, low volatility and moisture-retaining properties makes Propylene Glycol an important chemical raw material for both industrial and specialty applications.